Strategic Applications of Ultra-Cold Atoms

DTIC Science & Technology

2008-03-07

journals or in conference proceedings (N/A for none) 68.00Number of Papers published in peer-reviewed journals: Wolfgang Ketterle: New Frontiers with...Helmerson, V.S. Bagnato (American Institute of Physics, 2005) pp. 25-29. Wolfgang Ketterle: The Bose-Einstein Condensate- a Superfluid Gas of Coherent Atoms...Vuletic 0.10 No Wolfgang Ketterle 0.10 Yes David Pritchard 0.10 Yes Mara Prentiss 0.10 No 0.80FTE Equivalent: 8Total Number: Names of Under

EDITORIAL: Focus on Cold and Ultracold Molecules FOCUS ON COLD AND ULTRACOLD MOLECULES

NASA Astrophysics Data System (ADS)

Carr, Lincoln D.; Ye, Jun

2009-05-01

Cold and ultracold molecules are the next wave of ultracold physics, giving rise to an exciting array of scientific opportunities, including many body physics for novel quantum phase transitions, new states of matter, and quantum information processing. Precision tests of fundamental physical laws benefit from the existence of molecular internal structure with exquisite control. The study of novel collision and reaction dynamics will open a new chapter of quantum chemistry. Cold molecules bring together researchers from a variety of fields, including atomic, molecular, and optical physics, chemistry and chemical physics, quantum information science and quantum simulations, condensed matter physics, nuclear physics, and astrophysics, a truly remarkable synergy of scientific explorations. For the past decade there have been steady advances in direct cooling techniques, from buffer-gas cooling to cold molecular beams to electro- and magneto-molecular decelerators. These techniques have allowed a large variety of molecules to be cooled for pioneering studies. Recent amazing advances in experimental techniques combining the ultracold and the ultraprecise have furthermore brought molecules to the point of quantum degeneracy. These latter indirect cooling techniques magnetically associate atoms from a Bose-Einstein condensate and/or a quantum degenerate Fermi gas, transferring at 90% efficiency highly excited Fano-Feshbach molecules, which are on the order of 10 000 Bohr radii in size, to absolute ground state molecules just a few Bohr across. It was this latter advance, together with significant breakthroughs in internal state manipulations, which inspired us to coordinate this focus issue now, and is the reason why we say the next wave of ultracold physics has now arrived. Whether directly or indirectly cooled, heteronuclear polar molecules offer distinct new features in comparison to cold atoms, while sharing all of their advantages (purity, high coherence, controllability, tunable interactions, no disorder, etc). First, they are more easily manipulated because of the strong response of their electric dipole moment to external electric fields, DC or AC. The electric dipole moment also creates the new aspect of long range interactions. Second, they have a rich internal structure, with vibrational and rotational states, fine or hyperfine structure, and Ω- or Λ-doublets. This internal structure allows for wonderful new possibilities in areas such as precision measurement and exquisite control of system dynamics. Therefore, although this focus issue contains a few articles on homonuclear molecules, more complex molecules such as benzene, and even a contribution on atomic chromium, which has a significant magnetic dipole moment, our main focus is on the heteronuclear polar case. This focus issue explores both direct and indirect cooling of mainly polar molecules, and the theory to support and inspire these advances. Thirty-eight research groups have contributed original work, and there are two review articles to complement these advances: the first covers cold and ultracold molecules broadly from few body to many body physics, including foundational theory, the technology to make them, and their scientific applications. The second is on the search for time variation of fundamental constants. The former review, which is comprehensive in nature, concludes with a list of open questions. This sets the tone for the focus issue, namely, openness, innovation, and possibility, an emphasis for which New Journal of Physics, an open-access journal of the highest quality, is especially fitted. Focus on Cold and Ultracold Molecules Contents Cold and ultracold molecules: science, technology and applications Lincoln D Carr, David DeMille, Roman V Krems and Jun Ye Ultracold molecules: new probes on the variation of fundamental constants Cheng Chin, V V Flambaum and M G Kozlov Probing the unitarity limit at low laser intensities Philippe Pellegrini and Robin Côté Single-photon molecular cooling Edvardas Narevicius, S Travis Bannerman and Mark G Raizen Quantum simulations of extended Hubbard models with dipolar crystals M Ortner, A Micheli, G Pupillo and P Zoller Collisional and molecular spectroscopy in an ultracold Bose-Bose mixture G Thalhammer, G Barontini, J Catani, F Rabatti, C Weber, A Simoni, F Minardi and M Inguscio Multi-channel modelling of the formation of vibrationally cold polar KRb molecules Svetlana Kotochigova, Eite Tiesinga and Paul S Julienne Formation of ultracold, highly polar X1Σ+ NaCs molecules C Haimberger, J Kleinert, P Zabawa, A Wakim and N P Bigelow Quantum polarization spectroscopy of correlations in attractive fermionic gases T Roscilde, M Rodríguez, K Eckert, O Romero-Isart, M Lewenstein, E Polzik and A Sanpera Inelastic semiclassical collisions in cold dipolar gases Michael Cavagnero and Catherine Newell Quasi-universal dipolar scattering in cold and ultracold gases J L Bohn, M Cavagnero and C Ticknor Stark deceleration of lithium hydride molecules S K Tokunaga, J M Dyne, E A Hinds and M R Tarbutt Molecular vibrational cooling by optical pumping with shaped femtosecond pulses D Sofikitis, S Weber, A Fioretti, R Horchani, M Allegrini, B Chatel, D Comparat and P Pillet Deeply bound ultracold molecules in an optical lattice Johann G Danzl, Manfred J Mark, Elmar Haller, Mattias Gustavsson, Russell Hart, Andreas Liem, Holger Zellmer and Hanns-Christoph Nägerl Toward the production of quantum degenerate bosonic polar molecules, 41K87Rb K Aikawa, D Akamatsu, J Kobayashi, M Ueda, T Kishimoto and S Inouye Influence of a Feshbach resonance on the photoassociation of LiCs J Deiglmayr, P Pellegrini, A Grochola, M Repp, R Côté, O Dulieu, R Wester and M Weidemüller The kinematic cooling of molecules with laser-cooled atoms Ken Takase, Larry A Rahn, David W Chandler and Kevin E Strecker Coherent collapses of dipolar Bose-Einstein condensates for different trap geometries J Metz, T Lahaye, B Fröhlich, A Griesmaier, T Pfau, H Saito, Y Kawaguchi and M Ueda High-energy-resolution molecular beams for cold collision studies L P Parazzoli, N Fitch, D S Lobser and H J Lewandowski Collisional effects in the formation of cold guided beams of polar molecules M Motsch, C Sommer, M Zeppenfeld, L D van Buuren, P W H Pinkse and G Rempe Towards sympathetic cooling of large molecules: cold collisions between benzene and rare gas atoms P Barletta, J Tennyson and P F Barker Efficient formation of ground-state ultracold molecules via STIRAP from the continuum at a Feshbach resonance Elena Kuznetsova, Marko Gacesa, Philippe Pellegrini, Susanne F Yelin and Robin Côté Emergent timescales in entangled quantum dynamics of ultracold molecules in optical lattices M L Wall and L D Carr Rotational state resolved photodissociation spectroscopy of translationally and vibrationally cold MgH+ ions: toward rotational cooling of molecular ions K Højbjerre, A K Hansen, P S Skyt, P F Staanum and M Drewsen Collective transverse cavity cooling of a dense molecular beam Thomas Salzburger and Helmut Ritsch A Stark decelerator on a chip Samuel A Meek, Horst Conrad and Gerard Meijer Deceleration of molecules by dipole force potential: a numerical simulation Susumu Kuma and Takamasa Momose Ultracold molecules: vehicles to scalable quantum information processing Kathy-Anne Brickman Soderberg, Nathan Gemelke and Cheng Chin Magnetic field modification of ultracold molecule-molecule collisions T V Tscherbul, Yu V Suleimanov, V Aquilanti and R V Krems Spectroscopy of 39K85Rb triplet excited states using ultracold a 3Σ+ state molecules formed by photoassociation J T Kim, D Wang, E E Eyler, P L Gould and W C Stwalley Pumping vortex into a Bose-Einstein condensate of heteronuclear molecules Z F Xu, R Q Wang and L You Intense atomic and molecular beams via neon buffer-gas cooling David Patterson, Julia Rasmussen and John M Doyle Dynamical properties of dipolar Fermi gases T Sogo, L He, T Miyakawa, S Yi, H Lu and H Pu Collisions of bosonic ultracold polar molecules in microwave traps Alexander V Avdeenkov Cold TiO(X3Δ)-He collisions Mei-Ju Lu and Jonathan D Weinstein Investigation of dephasing rates in an interacting Rydberg gas U Raitzsch, R Heidemann, H Weimer, B Butscher, P Kollmann, R Löw, H P Büchler and T Pfau Impact of electric fields on highly excited rovibrational states of polar dimers Rosario González-Férez and Peter Schmelcher Phase transition from straight into twisted vortex lines in dipolar Bose-Einstein condensates M Klawunn and L Santos Stimulating the production of deeply bound RbCs molecules with laser pulses: the role of spin-orbit coupling in forming ultracold molecules Subhas Ghosal, Richard J Doyle, Christiane P Koch and Jeremy M Hutson Sensitive measurement of mp/me variance using vibrational transition frequencies of cold molecules Masatoshi Kajita

An apparatus for immersing trapped ions into an ultracold gas of neutral atoms

NASA Astrophysics Data System (ADS)

Schmid, Stefan; Härter, Arne; Frisch, Albert; Hoinka, Sascha; Denschlag, Johannes Hecker

2012-05-01

We describe a hybrid vacuum system in which a single ion or a well-defined small number of trapped ions (in our case Ba+ or Rb+) can be immersed into a cloud of ultracold neutral atoms (in our case Rb). This apparatus allows for the study of collisions and interactions between atoms and ions in the ultracold regime. Our setup is a combination of a Bose-Einstein condensation apparatus and a linear Paul trap. The main design feature of the apparatus is to first separate the production locations for the ion and the ultracold atoms and then to bring the two species together. This scheme has advantages in terms of stability and available access to the region where the atom-ion collision experiments are carried out. The ion and the atoms are brought together using a moving one-dimensional optical lattice transport which vertically lifts the atomic sample over a distance of 30 cm from its production chamber into the center of the Paul trap in another chamber. We present techniques to detect and control the relative position between the ion and the atom cloud.

Universality and Quantum Criticality of the One-Dimensional Spinor Bose Gas

NASA Astrophysics Data System (ADS)

PâÅ£u, Ovidiu I.; Klümper, Andreas; Foerster, Angela

2018-06-01

We investigate the universal thermodynamics of the two-component one-dimensional Bose gas with contact interactions in the vicinity of the quantum critical point separating the vacuum and the ferromagnetic liquid regime. We find that the quantum critical region belongs to the universality class of the spin-degenerate impenetrable particle gas which, surprisingly, is very different from the single-component case and identify its boundaries with the peaks of the specific heat. In addition, we show that the compressibility Wilson ratio, which quantifies the relative strength of thermal and quantum fluctuations, serves as a good discriminator of the quantum regimes near the quantum critical point. Remarkably, in the Tonks-Girardeau regime, the universal contact develops a pronounced minimum, reflected in a counterintuitive narrowing of the momentum distribution as we increase the temperature. This momentum reconstruction, also present at low and intermediate momenta, signals the transition from the ferromagnetic to the spin-incoherent Luttinger liquid phase and can be detected in current experiments with ultracold atomic gases in optical lattices.

Role of thermal two-phonon scattering for impurity dynamics in a low-dimensional Bose-Einstein condensate

NASA Astrophysics Data System (ADS)

Lausch, Tobias; Widera, Artur; Fleischhauer, Michael

2018-03-01

We numerically study the relaxation dynamics of a single, heavy impurity atom interacting with a finite one- or two-dimensional, ultracold Bose gas. While there is a clear separation of time scales between processes resulting from single- and two-phonon scattering in three spatial dimensions, the thermalization in lower dimensions is dominated by two-phonon processes. This is due to infrared divergences in the corresponding scattering rates in the thermodynamic limit, which are a manifestation of the Mermin-Wagner-Hohenberg theorem. This makes it necessary to include second-order phonon scattering above a crossover temperature T2ph . T2ph scales inversely with the system size and is much smaller than currently experimentally accessible.

Dirac-, Rashba-, and Weyl-type spin-orbit couplings: Toward experimental realization in ultracold atoms

NASA Astrophysics Data System (ADS)

Wang, Bao-Zong; Lu, Yue-Hui; Sun, Wei; Chen, Shuai; Deng, Youjin; Liu, Xiong-Jun

2018-01-01

We propose a hierarchy set of minimal optical Raman lattice schemes to pave the way for experimental realization of high-dimensional spin-orbit (SO) couplings for ultracold atoms, including two-dimensional (2D) Dirac type, 2D Rashba type, and three-dimensional (3D) Weyl type. The proposed Dirac-type SO coupling exhibits precisely controllable high symmetry, for which a large topological phase region is predicted. The generation of 2D Rashba and 3D Weyl types requires that two sources of laser beams have distinct frequencies of factor 2 difference. Surprisingly, we find that 133Cs atoms provide an ideal candidate for the realization. A common and essential feature is of high controllability and absent of any fine-tuning in the realization, and the resulting SO coupled ultracold atoms have a long lifetime. In particular, a long-lived topological Bose gas of 2D Dirac SO coupling has been proved in the follow-up experiment. These schemes essentially improve over the current experimental accessibility and controllability, and open a realistic way to explore novel high-dimensional SO physics, particularly quantum many-body physics and quantum far-from-equilibrium dynamics with novel topology for ultracold atoms.

Two-dimensional Fermi gas in spin-dependent magnetic fields

NASA Astrophysics Data System (ADS)

Anzai, Takaaki; Nishida, Yusuke

Experimental techniques in ultracold atoms allow us to tune parameters of the system at will. In particular, synthetic magnetic fields have been created by using the atom-light coupling and, therefore, it is interesting to study what kinds of quantum phenomena appear in correlated ultracold atoms subjected to synthetic magnetic fields. In this work, we consider a two-dimensional Fermi gas with two spin states in spin-dependent magnetic fields which are assumed to be antiparallel for different spin states. By studying the ground-state phase diagram within the mean-field approximation, we find quantum spin Hall and superfluid phases separated by a second-order phase transition. We also show that there are regions where the superfluid gap parameter is proportional to the attractive coupling, which is in marked contrast to the usual exponential dependence. Moreover, we elucidate that the universality class of the phase transition belongs to that of the XY model at special points of the phase boundary, while it belongs to that of a dilute Bose gas anywhere else. International Research Center for Nanoscience and Quantum Physics, Tokyo Institute of Technology.

Fundamental Physics

NASA Image and Video Library

2003-02-09

This image depicts the formation of multiple whirlpools in a sodium gas cloud. Scientists who cooled the cloud and made it spin created the whirlpools in a Massachusetts Institute of Technology laboratory, as part of NASA-funded research. This process is similar to a phenomenon called starquakes that appear as glitches in the rotation of pulsars in space. MIT's Wolgang Ketterle and his colleagues, who conducted the research under a grant from the Biological and Physical Research Program through NASA's Jet Propulsion Laboratory, Pasadena, Calif., cooled the sodium gas to less than one millionth of a degree above absolute zero (-273 Celsius or -460 Fahrenheit). At such extreme cold, the gas cloud converts to a peculiar form of matter called Bose-Einstein condensate, as predicted by Albert Einstein and Satyendra Bose of India in 1927. No physical container can hold such ultra-cold matter, so Ketterle's team used magnets to keep the cloud in place. They then used a laser beam to make the gas cloud spin, a process Ketterle compares to stroking a ping-pong ball with a feather until it starts spirning. The spinning sodium gas cloud, whose volume was one- millionth of a cubic centimeter, much smaller than a raindrop, developed a regular pattern of more than 100 whirlpools.

Mean-field scaling of the superfluid to Mott insulator transition in a 2D optical superlattice.

NASA Astrophysics Data System (ADS)

Okano, Masayuki; Thomas, Claire; Barter, Thomas; Leung, Tsz-Him; Jo, Gyu-Boong; Guzman, Jennie; Kimchi, Itamar; Vishwanath, Ashvin; Stamper-Kurn, Dan

2017-04-01

Quantum gases within optical lattices provide a nearly ideal experimental representation of the Bose-Hubbard model. The mean-field treatment of this model predicts properties of non-zero temperature lattice-trapped gasses to be insensitive to the specific lattice geometry once system energies are scaled by the lattice coordination number z. We examine an ultracold Bose gas of rubidium atoms prepared within a two-dimensional lattice whose geometry can be tuned between two configurations, triangular and kagome, for which z varies from six to four, respectively. Measurements of the coherent fraction of the gas thereby provide a quantitative test of the mean-field scaling prediction. We observe the suppression of superfluidity upon decreasing z, and find our results to be consistent with the predicted mean-field scaling. These optical lattice systems can offer a way to study paradigmatic solid-state phenomena in highly controlled crystal structures. This work was supported by the NSF and by the Army Research Office with funding from the DARPA OLE program.

Ultra-Cold Atoms on Optical Lattices

ERIC Educational Resources Information Center

Ghosh, Parag

2009-01-01

The field of ultra-cold atoms, since the achievement of Bose-Einstein Condensation (Anderson et al., 1995; Davis et al., 1995; Bradley et al., 1995), have seen an immensely growing interest over the past decade. With the creation of optical lattices, new possibilities of studying some of the widely used models in condensed matter have opened up.…

Bose-Einstein condensation. Twenty years after

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bagnato, V. S.; Frantzeskakis, D. J.; Kevrekidis, P. G.

The aim of this introductory article is two-fold. First, we aim to offer a general introduction to the theme of Bose-Einstein condensates, and briefly discuss the evolution of a number of relevant research directions during the last two decades. Second, we introduce and present the articles that appear in this Special Volume of Romanian Reports in Physics celebrating the conclusion of the second decade since the experimental creation of Bose-Einstein condensation in ultracold gases of alkali-metal atoms.

Bose-Einstein condensation. Twenty years after

DOE PAGES

Bagnato, V. S.; Frantzeskakis, D. J.; Kevrekidis, P. G.; ...

2015-02-23

The aim of this introductory article is two-fold. First, we aim to offer a general introduction to the theme of Bose-Einstein condensates, and briefly discuss the evolution of a number of relevant research directions during the last two decades. Second, we introduce and present the articles that appear in this Special Volume of Romanian Reports in Physics celebrating the conclusion of the second decade since the experimental creation of Bose-Einstein condensation in ultracold gases of alkali-metal atoms.

Excess Noise Depletion of a Bose-Einstein Condensate in an Optical Cavity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Szirmai, G.; Nagy, D.; Domokos, P.

2009-02-27

Quantum fluctuations of a cavity field coupled into the motion of ultracold bosons can be strongly amplified by a mechanism analogous to the Petermann excess noise factor in lasers with unstable cavities. For a Bose-Einstein condensate in a stable optical resonator, the excess noise effect amounts to a significant depletion on long time scales.

Artist's Rendering of Multiple Whirlpools in a Sodium Gas Cloud

NASA Technical Reports Server (NTRS)

2003-01-01

This image depicts the formation of multiple whirlpools in a sodium gas cloud. Scientists who cooled the cloud and made it spin created the whirlpools in a Massachusetts Institute of Technology laboratory, as part of NASA-funded research. This process is similar to a phenomenon called starquakes that appear as glitches in the rotation of pulsars in space. MIT's Wolgang Ketterle and his colleagues, who conducted the research under a grant from the Biological and Physical Research Program through NASA's Jet Propulsion Laboratory, Pasadena, Calif., cooled the sodium gas to less than one millionth of a degree above absolute zero (-273 Celsius or -460 Fahrenheit). At such extreme cold, the gas cloud converts to a peculiar form of matter called Bose-Einstein condensate, as predicted by Albert Einstein and Satyendra Bose of India in 1927. No physical container can hold such ultra-cold matter, so Ketterle's team used magnets to keep the cloud in place. They then used a laser beam to make the gas cloud spin, a process Ketterle compares to stroking a ping-pong ball with a feather until it starts spirning. The spinning sodium gas cloud, whose volume was one- millionth of a cubic centimeter, much smaller than a raindrop, developed a regular pattern of more than 100 whirlpools.

Two-stage crossed beam cooling with ⁶Li and ¹³³Cs atoms in microgravity.

PubMed

Luan, Tian; Yao, Hepeng; Wang, Lu; Li, Chen; Yang, Shifeng; Chen, Xuzong; Ma, Zhaoyuan

2015-05-04

Applying the direct simulation Monte Carlo (DSMC) method developed for ultracold Bose-Fermi mixture gases research, we study the sympathetic cooling process of 6Li and 133Cs atoms in a crossed optical dipole trap. The obstacles to producing 6Li Fermi degenerate gas via direct sympathetic cooling with 133Cs are also analyzed, by which we find that the side-effect of the gravity is one of the main obstacles. Based on the dynamic nature of 6Li and 133Cs atoms, we suggest a two-stage cooling process with two pairs of crossed beams in microgravity environment. According to our simulations, the temperature of 6Li atoms can be cooled to T = 29.5 pK and T/TF = 0.59 with several thousand atoms, which propose a novel way to get ultracold fermion atoms with quantum degeneracy near pico-Kelvin.

Dark soliton pair of ultracold Fermi gases for a generalized Gross-Pitaevskii equation model.

PubMed

Wang, Ying; Zhou, Yu; Zhou, Shuyu; Zhang, Yongsheng

2016-07-01

We present the theoretical investigation of dark soliton pair solutions for one-dimensional as well as three-dimensional generalized Gross-Pitaevskii equation (GGPE) which models the ultracold Fermi gas during Bardeen-Cooper-Schrieffer-Bose-Einstein condensates crossover. Without introducing any integrability constraint and via the self-similar approach, the three-dimensional solution of GGPE is derived based on the one-dimensional dark soliton pair solution, which is obtained through a modified F-expansion method combined with a coupled modulus-phase transformation technique. We discovered the oscillatory behavior of the dark soliton pair from the theoretical results obtained for the three-dimensional case. The calculated period agrees very well with the corresponding reported experimental result [Weller et al., Phys. Rev. Lett. 101, 130401 (2008)PRLTAO0031-900710.1103/PhysRevLett.101.130401], demonstrating the applicability of the theoretical treatment presented in this work.

Quantum noise of a Bose-Einstein condensate in an optical cavity, correlations, and entanglement

NASA Astrophysics Data System (ADS)

Szirmai, G.; Nagy, D.; Domokos, P.

2010-04-01

A Bose-Einstein condensate of ultracold atoms inside the field of a laser-driven optical cavity exhibits dispersive optical bistability. We describe this system by using mean-field approximation and by analyzing the correlation functions of the linearized quantum fluctuations around the mean-field solution. The entanglement and the statistics of the atom-field quadratures are given in the stationary state. It is shown that the mean-field solution, that is, the Bose-Einstein condensate, is robust against entanglement generation for most of the phase diagram.

Universal Themes of Bose-Einstein Condensation

NASA Astrophysics Data System (ADS)

Proukakis, Nick P.; Snoke, David W.; Littlewood, Peter B.

2017-04-01

Foreword; List of contributors; Preface; Part I. Introduction: 1. Universality and Bose-Einstein condensation: perspectives on recent work D. W. Snoke, N. P. Proukakis, T. Giamarchi and P. B. Littlewood; 2. A history of Bose-Einstein condensation of atomic hydrogen T. Greytak and D. Kleppner; 3. Twenty years of atomic quantum gases: 1995-2015 W. Ketterle; 4. Introduction to polariton condensation P. B. Littlewood and A. Edelman; Part II. General Topics: Editorial notes; 5. The question of spontaneous symmetry breaking in condensates D. W. Snoke and A. J. Daley; 6. Effects of interactions on Bose-Einstein condensation R. P. Smith; 7. Formation of Bose-Einstein condensates M. J. Davis, T. M. Wright, T. Gasenzer, S. A. Gardiner and N. P. Proukakis; 8. Quenches, relaxation and pre-thermalization in an isolated quantum system T. Langen and J. Schmiedmayer; 9. Ultracold gases with intrinsic scale invariance C. Chin; 10. Berezinskii-Kosterlitz-Thouless phase of a driven-dissipative condensate N. Y. Kim, W. H. Nitsche and Y. Yamamoto; 11. Superfluidity and phase correlations of driven dissipative condensates J. Keeling, L. M. Sieberer, E. Altman, L. Chen, S. Diehl and J. Toner; 12. BEC to BCS crossover from superconductors to polaritons A. Edelman and P. B. Littlewood; Part III. Condensates in Atomic Physics: Editorial notes; 13. Probing and controlling strongly correlated quantum many-body systems using ultracold quantum gases I. Bloch; 14. Preparing and probing chern bands with cold atoms N. Goldman, N. R. Cooper and J. Dalibard; 15. Bose-Einstein condensates in artificial gauge fields L. J. LeBlanc and I. B. Spielman; 16. Second sound in ultracold atomic gases L. Pitaevskii and S. Stringari; 17. Quantum turbulence in atomic Bose-Einstein condensates N. G. Parker, A. J. Allen, C. F. Barenghi and N. P. Proukakis; 18. Spinor-dipolar aspects of Bose-Einstein condensation M. Ueda; Part IV. Condensates in Condensed Matter Physics: Editorial notes; 19. Bose-Einstein condensation of photons and grand-canonical condensate fluctuations J. Klaers and M. Weitz; 20. Laser operation and Bose-Einstein condensation: analogies and differences A. Chiocchetta, A. Gambassi and I. Carusotto; 21. Vortices in resonant polariton condensates in semiconductor microcavities D. N. Krizhanovskii, K. Guda, M. Sich, M. S. Skolnick, L. Dominici and D. Sanvitto; 22. Optical control of polariton condensates G. Christmann, P. G. Savvidis and J. J. Baumberg; 23. Disorder, synchronization and phase-locking in non-equilibrium Bose-Einstein condensates P. R. Eastham and B. Rosenow; 24. Collective topological excitations in 1D polariton quantum fluids H. Terças, D. D. Solnyshkov and G. Malpuech; 25. Microscopic theory of Bose-Einstein condensation of magnons at room temperature H. Salman, N. G. Berloff and S. O. Demokritov; 26. Spintronics and magnon Bose-Einstein condensation R. A. Duine, A. Brataas, S. A. Bender and Y. Tserkovnyak; 27. Spin-superfluidity and spin-current mediated non-local transport H. Chen and A. H. MacDonald; 28. Bose-Einstein condensation in quantum magnets C. Kollath, T. Giamarchi and C. Rüegg; Part V. Condensates in Astrophysics and Cosmology: Editorial notes; 29. Bose-Einstein condensates in neutron stars C. J. Pethick, T. Schäfer and A. Schwenk; 30. A simulated cosmological metric: the superfluid 3He condensate G. R. Pickett; 31. Cosmic axion Bose-Einstein condensation N. Banik and P. Sikivie; 32. Graviton BECs: a new approach to quantum gravity G. Dvali and C. Gomez; Universal Bose-Einstein condensation workshop; Index.

All-optical spinor Bose-Einstein condensation and the spinor dynamics-driven atom laser

NASA Astrophysics Data System (ADS)

Lundblad, Nathan Eric

Optical trapping as a viable means of exploring the physics of ultracold dilute atomic gases has revealed a new spectrum of physical phenomena. In particular, macroscopic and sudden occupation of the ground state below a critical temperature---a phenomenon known as Bose-Einstein condensation---has become an even richer system for the study of quantum mechanics, ultracold collisions, and many-body physics in general. Optical trapping liberates the spin degree of the BEC, making the order parameter vectorial ('spinor BEC'), as opposed to the scalar order of traditional magnetically trapped condensates. The work described within is divided into two main efforts. The first encompasses the all-optical creation of a Bose-Einstein condensate in rubidium vapor. An all-optical path to spinor BEC (as opposed to transfer to an optical trap from a magnetic trap condensate) was desired both for the simplicity of the experimental setup and also for the potential gains in speed of creation; evaporative cooling, the only known path to dilute-gas condensation, works only as efficiently as the rate of elastic collisions in the gas, a rate that starts out much higher in optical traps. The first all-optical BEC was formed elsewhere in 2001; the years following saw many groups worldwide seeking to create their own version. Our own all-optical spinor BEC, made with a single-beam dipole trap formed by a focused CO2 laser, is described here, with particular attention paid to trap loading, measurement of trap parameters, and the use of a novel 780 nm high-power laser system. The second part describes initial experiments performed with the nascent condensate. The spinor properties of the condensate are documented, and a measurement is made of the density-dependent rate of spin mixing in the condensate. In addition, we demonstrate a novel dual-beam atom laser formed by outcoupling oppositely polarized components of the condensate, whose populations have been coherently evolved through spin dynamics. We drive coherent spin-mixing evolution through adiabatic compression of the initially weak trap. Such dual beams, nominally number-correlated through the angular momentum-conserving collision 2m0 ⇋ m+1 + m-1 have been proposed as tools to explore entanglement and squeezing in Bose-Einstein condensates.

Stochastic and equilibrium pictures of the ultracold Fano-Feshbach-resonance molecular conversion rate

NASA Astrophysics Data System (ADS)

Yamakoshi, Tomotake; Watanabe, Shinichi; Zhang, Chen; Greene, Chris H.

2013-05-01

The ultracold molecular conversion rate occurring in an adiabatic ramp through a Fano-Feshbach resonance is studied and compared in two statistical models. One model, the so-called stochastic phase-space sampling (SPSS) [Hodby , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.94.120402 94, 120402 (2005)] evaluates the overlap of two atomic distributions in phase space by sampling atomic pairs according to a phase-space criterion. The other model, the chemical equilibrium theory (ChET) [Watabe and Nikuni, Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.77.013616 77, 013616 (2008)] considers atomic and molecular distributions in the limit of the chemical and thermal equilibrium. The present study applies SPSS and ChET to a prototypical system of K+K→ K2 in all the symmetry combinations, namely Fermi-Fermi, Bose-Bose, and Bose-Fermi cases. To examine implications of the phase-space criterion for SPSS, the behavior of molecular conversion is analyzed using four distinct geometrical constraints. Our comparison of the results of SPSS with those of ChET shows that while they appear similar in most situations, the two models give rise to rather dissimilar behaviors when the presence of a Bose-Einstein condensate strongly affects the molecule formation.

Coherent all-optical control of ultracold atoms arrays in permanent magnetic traps.

PubMed

Abdelrahman, Ahmed; Mukai, Tetsuya; Häffner, Hartmut; Byrnes, Tim

2014-02-10

We propose a hybrid architecture for quantum information processing based on magnetically trapped ultracold atoms coupled via optical fields. The ultracold atoms, which can be either Bose-Einstein condensates or ensembles, are trapped in permanent magnetic traps and are placed in microcavities, connected by silica based waveguides on an atom chip structure. At each trapping center, the ultracold atoms form spin coherent states, serving as a quantum memory. An all-optical scheme is used to initialize, measure and perform a universal set of quantum gates on the single and two spin-coherent states where entanglement can be generated addressably between spatially separated trapped ultracold atoms. This allows for universal quantum operations on the spin coherent state quantum memories. We give detailed derivations of the composite cavity system mediated by a silica waveguide as well as the control scheme. Estimates for the necessary experimental conditions for a working hybrid device are given.

Quantum Many-Body Dynamics with Driven Bose Condensates: Kibble-Zurek Mechanism and Bose Fireworks

NASA Astrophysics Data System (ADS)

Clark, Logan William

In recent years there has been an explosion of interest in the field of quantum many-body physics. Understanding the complex and often unintuitive behavior of systems containing interacting quantum constituents is not only fascinating but also crucial for developing the next generation of quantum technology, including better materials, sensors, and computers. Yet understanding such systems remains a challenge, particularly when considering the dynamics which occur when they are excited far from equilibrium. Ultracold atomic gases provide an ideal system with which to study dynamics by enabling clean, well-controlled experiments at length- and time-scales which allow us to observe the dynamics directly. This thesis describes experiments on the many-body dynamics of ultracold, bosonic cesium atoms. Our apparatus epitomizes the versatility of ultracold atoms by providing extensive control over the quantum gas. In particular, we will discuss our use of a digital micromirror device to project arbitrary, dynamic external potentials onto the gas; our development of a powerful new scheme for optically controlling Feshbach resonances to enable spatiotemporal control of the interactions between atoms; and our use of near-resonant shaking lattices to modify the kinetic energy of atoms. Taking advantage of this flexible apparatus, we have been able to test a longstanding conjecture based on the Kibble-Zurek mechanism, which says that the dynamics of a system crossing a quantum phase transition should obey a universal scaling symmetry of space and time. After accounting for this scaling symmetry, critical dynamics would be essentially independent of the rate at which a system crossed a phase transition. We tested the universal scaling of critical dynamics by using near-resonant shaking to drive Bose-Einstein condensates across an effectively ferromagnetic quantum phase transition. After crossing the phase transition, condensates divide themselves spatially into domains with finite quasimomentum. We measured the growth of these domains over time and the correlation functions describing their spatial distribution by directly reconstructing the quasimomentum distribution. We observed the expected scaling laws across more than an order of magnitude in the crossing rate, aside from which the observed critical dynamics were indeed independent of the crossing rate. These experiments provide strong support for the universal scaling symmetry of space and time and the extension of the Kibble-Zurek mechanism to quantum phase transitions. We also present the first observation of Bose Fireworks: the sudden emission of many bright, narrow jets of atoms from condensates with oscillating interaction strength. Even though the underlying inelastic s-wave collisions induced by oscillating interactions are isotropic, the collective nature of collisions in the condensate causes the outgoing bosonic atoms to bunch into narrow jets in the horizontal plane. This bunching results from runaway stimulated collisions, which we find can only occur above a threshold oscillation amplitude. The observed atom number in the jets suggests that they are seeded by quantum fluctuations. Moreover, in azimuthal correlation functions we observe forward correlations consistent with theory, which saturate the limit from the uncertainty principle. We also observe partial correlation between counterpropagating jets. Bose Fireworks provide a well-controlled platform for understanding the diverse class of systems in which a coherent source rapidly emits pairs of counterpropagating bosons.

Coherent inflationary dynamics for Bose-Einstein condensates crossing a quantum critical point

NASA Astrophysics Data System (ADS)

Feng, Lei; Clark, Logan W.; Gaj, Anita; Chin, Cheng

2018-03-01

Quantum phase transitions, transitions between many-body ground states, are of extensive interest in research ranging from condensed-matter physics to cosmology1-4. Key features of the phase transitions include a stage with rapidly growing new order, called inflation in cosmology5, followed by the formation of topological defects6-8. How inflation is initiated and evolves into topological defects remains a hot topic of debate. Ultracold atomic gas offers a pristine and tunable platform to investigate quantum critical dynamics9-21. We report the observation of coherent inflationary dynamics across a quantum critical point in driven Bose-Einstein condensates. The inflation manifests in the exponential growth of density waves and populations in well-resolved momentum states. After the inflation stage, extended coherent dynamics is evident in both real and momentum space. We present an intuitive description of the quantum critical dynamics in our system and demonstrate the essential role of phase fluctuations in the formation of topological defects.

Nonlinear Schrödinger equations for Bose-Einstein condensates

NASA Astrophysics Data System (ADS)

Galati, Luigi; Zheng, Shijun

2013-10-01

The Gross-Pitaevskii equation, or more generally the nonlinear Schrödinger equation, models the Bose-Einstein condensates in a macroscopic gaseous superfluid wave-matter state in ultra-cold temperature. We provide analytical study of the NLS with L2 initial data in order to understand propagation of the defocusing and focusing waves for the BEC mechanism in the presence of electromagnetic fields. Numerical simulations are performed for the two-dimensional GPE with anisotropic quadratic potentials.

Specific heat and effects of strong pairing fluctuations in a superfluid Fermi atom gas in the BCS-BEC crossover region

NASA Astrophysics Data System (ADS)

van Wyk, Pieter; Inotani, Daisuke; Ohashi, Yoji

2018-03-01

We theoretically investigate the specific heat at constant volume C V in the BCS(Bardeen-Cooper-Schrieffer)-BEC(Bose-Einstein-condensation)-crossover regime of an ultracold Fermi gas, below the superfluid phase transition temperature T c. Within the strong-coupling framework developed by Nozières and Schmitt-Rink, we show that the temperature dependence of C V drastically changes as one passes through the crossover region, and is sensitive to strong fluctuations in the Cooper channel near the unitarity limit. We also compare our results to a recent experiment on a 6Li unitary Fermi gas. Since fluctuation effects are a crucial key in the BCS-BEC-crossover phenomenon, our results would be helpful in considering how the fermionic BCS superfluid changes into BEC with increasing the interaction strength, from the viewpoint of specific heat.

Multimode Bose-Hubbard model for quantum dipolar gases in confined geometries

NASA Astrophysics Data System (ADS)

Cartarius, Florian; Minguzzi, Anna; Morigi, Giovanna

2017-06-01

We theoretically consider ultracold polar molecules in a wave guide. The particles are bosons: They experience a periodic potential due to an optical lattice oriented along the wave guide and are polarized by an electric field orthogonal to the guide axis. The array is mechanically unstable by opening the transverse confinement in the direction orthogonal to the polarizing electric field and can undergo a transition to a double-chain (zigzag) structure. For this geometry we derive a multimode generalized Bose-Hubbard model for determining the quantum phases of the gas at the mechanical instability, taking into account the quantum fluctuations in all directions of space. Our model limits the dimension of the numerically relevant Hilbert subspace by means of an appropriate decomposition of the field operator, which is obtained from a field theoretical model of the linear-zigzag instability. We determine the phase diagrams of small systems using exact diagonalization and find that, even for tight transverse confinement, the aspect ratio between the two transverse trap frequencies controls not only the classical but also the quantum properties of the ground state in a nontrivial way. Convergence tests at the linear-zigzag instability demonstrate that our multimode generalized Bose-Hubbard model can catch the essential features of the quantum phases of dipolar gases in confined geometries with a limited computational effort.

Strong-coupling phases of the spin-orbit-coupled spin-1 Bose-Hubbard chain: Odd-integer Mott lobes and helical magnetic phases

NASA Astrophysics Data System (ADS)

Pixley, J. H.; Cole, William S.; Spielman, I. B.; Rizzi, Matteo; Das Sarma, S.

2017-10-01

We study the odd-integer filled Mott phases of a spin-1 Bose-Hubbard chain and determine their fate in the presence of a Raman induced spin-orbit coupling which has been achieved in ultracold atomic gases; this system is described by a quantum spin-1 chain with a spiral magnetic field. The spiral magnetic field initially induces helical order with either ferromagnetic or dimer order parameters, giving rise to a spiral paramagnet at large field. The spiral ferromagnet-to-paramagnet phase transition is in a universality class with critical exponents associated with the divergence of the correlation length ν ≈2 /3 and the order-parameter susceptibility γ ≈1 /2 . We solve the effective spin model exactly using the density-matrix renormalization group, and compare with both a large-S classical solution and a phenomenological Landau theory. We discuss how these exotic bosonic magnetic phases can be produced and probed in ultracold atomic experiments in optical lattices.

Bose and Fermi Gases of Ultracold Ytterbium in a Triangular Optical Lattice

NASA Astrophysics Data System (ADS)

Thobe, Alexander; Doerscher, Soeren; Hundt, Bastian; Kochanke, Andre; Becker, Christoph; Sengstock, Klaus

2013-05-01

Quantum gases of alkaline-earth like atoms such as Calcium, Strontium and Ytterbium (Yb) open up exciting new possibilities for the study of many body physics in optical lattices, ranging from SU(N) symmetric spin Hamiltonians to the Kondo Lattice Model. Here, we present experimental studies of ultracold bosonic and fermionic Yb quantum gases. Unlike other experiments studying ultracold alkaline earth-like atoms, we have implemented a 2D-MOT instead of a Zeeman slower as a source of cold atoms. From the 2D-MOT, operating on the broad 1S0 -->1P1 transtition, the atoms are directly loaded into the 3D-MOT operating on a narrow intercombination line. The atoms are then evaporatively cooled to quantum degeneracy in a crossed optical dipole trap. With this setup we routinely produce BECs and degenerate Fermi gases of different Yb isotopes. Moreover, we present first results on spectroscopy of an interacting fermi gas on the ultranarrow 1S0 -->3P0 clock transition in a magic wavelength optical lattice. In future experiments, this spectroscopy will serve as a versatile tool for interaction sensing and selective addressing of atoms in a wavelength tunable, state dependent, triangular optical lattice, which we are currently implementing. This work is supported by DFG within SFB 925 and GrK 1355, as well as EU FETOpen (iSense).

Studying non-equilibrium many-body dynamics using one-dimensional Bose gases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Langen, Tim; Gring, Michael; Kuhnert, Maximilian

2014-12-04

Non-equilibrium dynamics of isolated quantum many-body systems play an important role in many areas of physics. However, a general answer to the question of how these systems relax is still lacking. We experimentally study the dynamics of ultracold one-dimensional (1D) Bose gases. This reveals the existence of a quasi-steady prethermalized state which differs significantly from the thermal equilibrium of the system. Our results demonstrate that the dynamics of non-equilibrium quantum many-body systems is a far richer process than has been assumed in the past.

Analogue Hawking radiation in an exactly solvable model of BEC

NASA Astrophysics Data System (ADS)

Parola, Alberto; Tettamanti, Manuele; Cacciatori, Sergio L.

2017-09-01

Hawking radiation, the spontaneous emission of thermal photons from an event horizon, is one of the most intriguing and elusive predictions of field theory in curved spacetimes. A formally analogue phenomenon occurs at the supersonic transition of a fluid: in this respect, ultracold gases stand out among the most promising systems but the theoretical modelling of this effect has always been carried out in semiclassical approximation, borrowing part of the analysis from the gravitational analogy. Here we discuss the exact solution of a one-dimensional Bose gas flowing against an obstacle, showing that spontaneous phonon emission (the analogue of Hawking radiation) is predicted without reference to the gravitational analogy. Long after the creation of the obstacle, the fluid settles into a stationary state displaying the emission of sound waves (phonons) in the upstream direction. A careful analysis shows that a precise correspondence between this phenomenon and the spontaneous emission of radiation from an event horizon requires additional conditions to be met in future experiments aimed at identifying the occurrence of the Hawking-like mechanism in Bose-Einstein condensates.

Disordered Supersolids in the Extended Bose-Hubbard Model

DOE PAGES

Lin, Fei; Maier, T. A.; Scarola, V. W.

2017-10-06

The extended Bose-Hubbard model captures the essential properties of a wide variety of physical systems including ultracold atoms and molecules in optical lattices, Josephson junction arrays, and certain narrow band superconductors. It exhibits a rich phase diagram including a supersolid phase where a lattice solid coexists with a superfluid. We use quantum Monte Carlo to study the supersolid part of the phase diagram of the extended Bose-Hubbard model on the simple cubic lattice. We add disorder to the extended Bose-Hubbard model and find that the maximum critical temperature for the supersolid phase tends to be suppressed by disorder. But wemore » also find a narrow parameter window in which the supersolid critical temperature is enhanced by disorder. Our results show that supersolids survive a moderate amount of spatial disorder and thermal fluctuations in the simple cubic lattice.« less

Momentum distribution functions in ensembles: the inequivalence of microcannonical and canonical ensembles in a finite ultracold system.

PubMed

Wang, Pei; Xianlong, Gao; Li, Haibin

2013-08-01

It is demonstrated in many thermodynamic textbooks that the equivalence of the different ensembles is achieved in the thermodynamic limit. In this present work we discuss the inequivalence of microcanonical and canonical ensembles in a finite ultracold system at low energies. We calculate the microcanonical momentum distribution function (MDF) in a system of identical fermions (bosons). We find that the microcanonical MDF deviates from the canonical one, which is the Fermi-Dirac (Bose-Einstein) function, in a finite system at low energies where the single-particle density of states and its inverse are finite.

Interference, focusing and excitation of ultracold atoms

NASA Astrophysics Data System (ADS)

Kandes, M. C.; Fahy, B. M.; Williams, S. R.; Tally, C. H., IV; Bromley, M. W. J.

2011-05-01

One of the pressing technological challenges in atomic physics is to go orders-of-magnitude beyond the limits of photon-based optics by harnessing the wave-nature of dilute clouds of ultracold atoms. We have developed parallelised algorithms to perform numerical calculations of the Gross-Pitaevskii equation in up to three dimensions and with up to three components to simulate Bose-Einstein condensates. A wide-ranging array of the physics associated with atom optics-based systems will be presented including BEC-based Sagnac interferometry in circular waveguides, the focusing of BECs using Laguerre-Gauss beams, and the interactions between BECs and Ince-Gaussian laser beams and their potential applications. One of the pressing technological challenges in atomic physics is to go orders-of-magnitude beyond the limits of photon-based optics by harnessing the wave-nature of dilute clouds of ultracold atoms. We have developed parallelised algorithms to perform numerical calculations of the Gross-Pitaevskii equation in up to three dimensions and with up to three components to simulate Bose-Einstein condensates. A wide-ranging array of the physics associated with atom optics-based systems will be presented including BEC-based Sagnac interferometry in circular waveguides, the focusing of BECs using Laguerre-Gauss beams, and the interactions between BECs and Ince-Gaussian laser beams and their potential applications. Performed on computational resources via NSF grants PHY-0970127, CHE-0947087 and DMS-0923278.

Synthetic clock states generated in a Bose-Einstein condensate via continuous dynamical decoupling

NASA Astrophysics Data System (ADS)

Lundblad, Nathan; Trypogeorgos, Dimitrios; Valdes-Curiel, Ana; Marshall, Erin; Spielman, Ian

2017-04-01

Radiofrequency- or microwave-dressed states have been used in NV center and ion-trap experiments to extend coherence times, shielding qubits from magnetic field noise through a process known as continuous dynamical decoupling. Such field-insensitive dressed states, as applied in the context of ultracold neutral atoms, have applications related to the creation of novel phases of spin-orbit-coupled quantum matter. We present observations of such a protected dressed-state system in a Bose-Einstein condensate, including measurements of the dependence of the protection on rf coupling strength, and estimates of residual field sensitivities.

Experimental Observation of One-Dimensional Superradiance Lattices in Ultracold Atoms

NASA Astrophysics Data System (ADS)

Chen, Liangchao; Wang, Pengjun; Meng, Zengming; Huang, Lianghui; Cai, Han; Wang, Da-Wei; Zhu, Shi-Yao; Zhang, Jing

2018-05-01

We measure the superradiant emission in a one-dimensional (1D) superradiance lattice (SL) in ultracold atoms. Resonantly excited to a superradiant state, the atoms are further coupled to other collectively excited states, which form a 1D SL. The directional emission of one of the superradiant excited states in the 1D SL is measured. The emission spectra depend on the band structure, which can be controlled by the frequency and intensity of the coupling laser fields. This work provides a platform for investigating the collective Lamb shift of resonantly excited superradiant states in Bose-Einstein condensates and paves the way for realizing higher dimensional superradiance lattices.

Chladni solitons and the onset of the snaking instability for dark solitons in confined superfluids.

PubMed

Muñoz Mateo, A; Brand, J

2014-12-19

Complex solitary waves composed of intersecting vortex lines are predicted in a channeled superfluid. Their shapes in a cylindrical trap include a cross, spoke wheels, and Greek Φ, and trace the nodal lines of unstable vibration modes of a planar dark soliton in analogy to Chladni's figures of membrane vibrations. The stationary solitary waves extend a family of solutions that include the previously known solitonic vortex and vortex rings. Their bifurcation points from the dark soliton indicating the onset of new unstable modes of the snaking instability are predicted from scale separation for Bose-Einstein condensates (BECs) and superfluid Fermi gases across the BEC-BCS crossover, and confirmed by full numerical calculations. Chladni solitons could be observed in ultracold gas experiments by seeded decay of dark solitons.

Chladni Solitons and the Onset of the Snaking Instability for Dark Solitons in Confined Superfluids

NASA Astrophysics Data System (ADS)

Muñoz Mateo, A.; Brand, J.

2014-12-01

Complex solitary waves composed of intersecting vortex lines are predicted in a channeled superfluid. Their shapes in a cylindrical trap include a cross, spoke wheels, and Greek Φ , and trace the nodal lines of unstable vibration modes of a planar dark soliton in analogy to Chladni's figures of membrane vibrations. The stationary solitary waves extend a family of solutions that include the previously known solitonic vortex and vortex rings. Their bifurcation points from the dark soliton indicating the onset of new unstable modes of the snaking instability are predicted from scale separation for Bose-Einstein condensates (BECs) and superfluid Fermi gases across the BEC-BCS crossover, and confirmed by full numerical calculations. Chladni solitons could be observed in ultracold gas experiments by seeded decay of dark solitons.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Fei; Maier, T. A.; Scarola, V. W.

The extended Bose-Hubbard model captures the essential properties of a wide variety of physical systems including ultracold atoms and molecules in optical lattices, Josephson junction arrays, and certain narrow band superconductors. It exhibits a rich phase diagram including a supersolid phase where a lattice solid coexists with a superfluid. We use quantum Monte Carlo to study the supersolid part of the phase diagram of the extended Bose-Hubbard model on the simple cubic lattice. We add disorder to the extended Bose-Hubbard model and find that the maximum critical temperature for the supersolid phase tends to be suppressed by disorder. But wemore » also find a narrow parameter window in which the supersolid critical temperature is enhanced by disorder. Our results show that supersolids survive a moderate amount of spatial disorder and thermal fluctuations in the simple cubic lattice.« less

PT -symmetric gain and loss in a rotating Bose-Einstein condensate

NASA Astrophysics Data System (ADS)

Haag, Daniel; Dast, Dennis; Cartarius, Holger; Wunner, Günter

2018-03-01

PT -symmetric quantum mechanics allows finding stationary states in mean-field systems with balanced gain and loss of particles. In this work we apply this method to rotating Bose-Einstein condensates with contact interaction which are known to support ground states with vortices. Due to the particle exchange with the environment transport phenomena through ultracold gases with vortices can be studied. We find that even strongly interacting rotating systems support stable PT -symmetric ground states, sustaining a current parallel and perpendicular to the vortex cores. The vortices move through the nonuniform particle density and leave or enter the condensate through its borders creating the required net current.

Experimental investigation of early-time diffusion in the quantum kicked rotor using a Bose-Einstein condensate.

PubMed

Duffy, G J; Parkins, S; Müller, T; Sadgrove, M; Leonhardt, R; Wilson, A C

2004-11-01

We report measurements of the early-time momentum diffusion for the atom-optical delta-kicked rotor. In this experiment a Bose-Einstein condensate provides a source of ultracold atoms with an ultranarrow initial momentum distribution, which is then subjected to periodic pulses (or "kicks") using an intense far-detuned optical standing wave. We characterize the effect of varying the effective Planck's constant for the system, while keeping all other parameters fixed. The observed behavior includes both quantum resonances (ballistic energy growth) and antiresonances (re-establishment of the initial state). Our experimental results are compared with theoretical predictions.

Quantum entangled dark solitons formed by ultracold atoms in optical lattices.

PubMed

Mishmash, R V; Carr, L D

2009-10-02

Inspired by experiments on Bose-Einstein condensates in optical lattices, we study the quantum evolution of dark soliton initial conditions in the context of the Bose-Hubbard Hamiltonian. An extensive set of quantum measures is utilized in our analysis, including von Neumann and generalized quantum entropies, quantum depletion, and the pair correlation function. We find that quantum effects cause the soliton to fill in. Moreover, soliton-soliton collisions become inelastic, in strong contrast to the predictions of mean-field theory. These features show that the lifetime and collision properties of dark solitons in optical lattices provide clear signals of quantum effects.

Manipulation of ultracold Rb atoms using a single linearly chirped laser pulse.

PubMed

Collins, T A; Malinovskaya, S A

2012-06-15

At ultracold temperatures, atoms are free from thermal motion, which makes them ideal objects of investigations aiming to advance high-precision spectroscopy, metrology, quantum computation, producing Bose condensates, etc. The quantum state of ultracold atoms may be created and manipulated by making use of quantum control methods employing low-intensity pulses. We theoretically investigate population dynamics of ultracold Rb vapor induced by nanosecond linearly chirped pulses having kW/cm2 beam intensity and show a possibility of controllable population transfer between hyperfine (HpF) levels of 5(2)/S(1/2) state through Raman transitions. Satisfying the one-photon resonance condition with the lowest of the HpF states of 5(2)/P(1/2) or 5(2)/P(3/2) state allows us to enter the adiabatic region of population transfer at very low field intensities, such that corresponding Rabi frequencies are less than or equal to the HpF splitting. This methodology provides a robust way to create a specifically designed superposition state in Rb in the basis of HpF levels and perform state manipulation controllable on the picosecond-to-nanosecond time scale.

Magnon edge states in the hardcore- Bose-Hubbard model.

PubMed

Owerre, S A

2016-11-02

Quantum Monte Carlo (QMC) simulation has uncovered nonzero Berry curvature and bosonic edge states in the hardcore-Bose-Hubbard model on the gapped honeycomb lattice. The competition between the chemical potential and staggered onsite potential leads to an interesting quantum phase diagram comprising the superfluid phase, Mott insulator, and charge density wave insulator. In this paper, we present a semiclassical perspective of this system by mapping to a spin-1/2 quantum XY model. We give an explicit analytical origin of the quantum phase diagram, the Berry curvatures, and the edge states using semiclassical approximations. We find very good agreement between the semiclassical analyses and the QMC results. Our results show that the topological properties of the hardcore-Bose-Hubbard model are the same as those of magnon in the corresponding quantum spin system. Our results are applicable to systems of ultracold bosonic atoms trapped in honeycomb optical lattices.

Disordered Quantum Gases and Spin-Dependent Lattices

DTIC Science & Technology

2013-07-07

regarding the role of disorder in many-particle quantum systems, such as superconductors and electronic solids. These issues are of great technological...REPORT Disordered Quantum Gases and Spin-Dependent Lattices 14. ABSTRACT 16. SECURITY CLASSIFICATION OF: This grant supported the first realization of...the disordered Bose-Hubbard models using ultra-cold atoms trapped in a disordered optical lattice. Several critical questions regarding this crucial

Critical behavior of a relativistic Bose gas.

PubMed

Pandita, P N

2014-03-01

We show that the thermodynamic behavior of relativistic ideal Bose gas, recently studied numerically by Grether et al., can be obtained analytically. Using the analytical results, we obtain the critical behavior of the relativistic Bose gas exactly for all the regimes. We show that these analytical results reduce to those of Grether et al. in different regimes of the Bose gas. Furthermore, we also obtain an analytically closed-form expression for the energy density for the Bose gas that is valid in all regimes.

Thermo-optical interactions in a dye-microcavity photon Bose-Einstein condensate

NASA Astrophysics Data System (ADS)

Alaeian, Hadiseh; Schedensack, Mira; Bartels, Clara; Peterseim, Daniel; Weitz, Martin

2017-11-01

Superfluidity and Bose-Einstein condensation are usually considered as two closely related phenomena. Indeed, in most macroscopic quantum systems, like liquid helium, ultracold atomic Bose gases, and exciton-polaritons, condensation and superfluidity occur in parallel. In photon Bose-Einstein condensates realized in the dye microcavity system, thermalization does not occur by direct interaction of the condensate particles as in the above described systems, i.e. photon-photon interactions, but by absorption and re-emission processes on the dye molecules, which act as a heat reservoir. Currently, there is no experimental evidence for superfluidity in the dye microcavity system, though effective photon interactions have been observed from thermo-optic effects in the dye medium. In this work, we theoretically investigate the implications of effective thermo-optic photon interactions, a temporally delayed and spatially non-local effect, on the photon condensate, and derive the resulting Bogoliubov excitation spectrum. The calculations suggest a linear photon dispersion at low momenta, fulfilling the Landau’s criterion of superfluidity. We envision that the temporally delayed and long-range nature of the thermo-optic photon interaction offer perspectives for novel quantum fluid phenomena.

Non-equilibrium dynamics of artificial quantum matter

NASA Astrophysics Data System (ADS)

Babadi, Mehrtash

The rapid progress of the field of ultracold atoms during the past two decades has set new milestones in our control over matter. By cooling dilute atomic gases and molecules to nano-Kelvin temperatures, novel quantum mechanical states of matter can be realized and studied on a table-top experimental setup while bulk matter can be tailored to faithfully simulate abstract theoretical models. Two of such models which have witnessed significant experimental and theoretical attention are (1) the two-component Fermi gas with resonant s-wave interactions, and (2) the single-component Fermi gas with dipole-dipole interactions. This thesis is devoted to studying the non-equilibrium collective dynamics of these systems using the general framework of quantum kinetic theory. We present a concise review of the utilized mathematical methods in the first two chapters, including the Schwinger-Keldysh formalism of non-equilibrium quantum fields, two-particle irreducible (2PI) effective actions and the framework of quantum kinetic theory. We study the collective dynamics of the dipolar Fermi gas in a quasi-two-dimensional optical trap in chapter 3 and provide a detailed account of its dynamical crossover from the collisionless to the hydrodynamical regime. Chapter 4 is devoted to studying the dynamics of the attractive Fermi gas in the normal phase. Starting from the self-consistent T-matrix (pairing fluctuation) approximation, we systematically derive a set of quantum kinetic equations and show that they provide a globally valid description of the dynamics of the attractive Fermi gas, ranging from the weak-coupling Fermi liquid phase to the intermediate non-Fermi liquid pairing pseudogap regime and finally the strong-coupling Bose liquid phase. The shortcomings of the self-consistent T-matrix approximation in two spatial dimensions are discussed along with a proposal to overcome its unphysical behaviors. The developed kinetic formalism is finally utilized to reproduce and interpret the findings of a recent experiment done on the collective dynamics of trapped two-dimensional ultracold gases.

Atom chip apparatus for experiments with ultracold rubidium and potassium gases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ivory, M. K.; Ziltz, A. R.; Fancher, C. T.

2014-04-15

We present a dual chamber atom chip apparatus for generating ultracold {sup 87}Rb and {sup 39}K atomic gases. The apparatus produces quasi-pure Bose-Einstein condensates of 10{sup 4} {sup 87}Rb atoms in an atom chip trap that features a dimple and good optical access. We have also demonstrated production of ultracold {sup 39}K and subsequent loading into the chip trap. We describe the details of the dual chamber vacuum system, the cooling lasers, the magnetic trap, the multicoil magnetic transport system, the atom chip, and two optical dipole traps. Due in part to the use of light-induced atom desorption, the lasermore » cooling chamber features a sufficiently good vacuum to also support optical dipole trap-based experiments. The apparatus is well suited for studies of atom-surface forces, quantum pumping and transport experiments, atom interferometry, novel chip-based traps, and studies of one-dimensional many-body systems.« less

Interaction-induced effects on Bose-Hubbard parameters

NASA Astrophysics Data System (ADS)

Kremer, Mark; Sachdeva, Rashi; Benseny, Albert; Busch, Thomas

2017-12-01

We study the effects of repulsive on-site interactions on the broadening of the localized Wannier functions used for calculating the parameters to describe ultracold atoms in optical lattices. For this, we replace the common single-particle Wannier functions, which do not contain any information about the interactions, by two-particle Wannier functions obtained from an exact solution which takes the interactions into account. We then use these interaction-dependent basis functions to calculate the Bose-Hubbard model parameters, showing that they are substantially different both at low and high lattice depths from the ones calculated using single-particle Wannier functions. Our results suggest that density effects are not negligible for many parameter ranges and need to be taken into account in metrology experiments.

Experiments with Ultracold Quantum-degenerate Fermionic Lithium Atoms

NASA Technical Reports Server (NTRS)

Ketterle, Wolfgang

2003-01-01

Experimental methods of laser and evaporative cooling, used in the production of atomic Bose-Einstein condensates have recently been extended to realize quantum degeneracy in trapped Fermi gases. Fermi gases are a new rich system to explore the implications of Pauli exclusion on scattering properties of the system, and ultimately fermionic superfluidity. We have produced a new macroscopic quantum system, in which a degenerate Li-6 Fermi gas coexists with a large and stable Na-23 BEC. This was accomplished using inter-species sympathetic cooling of fermionic 6Li in a thermal bath of bosonic Na-23. We have achieved high numbers of both fermions (less than 10(exp 5) and bosons (less than 10(exp 6), and Li-6 quantum degeneracy corresponding to one half of the Fermi temperature. This is the first time that a Fermi sea was produced with a condensate as a "refrigerator".

Exploring the Kibble-Zurek mechanism with homogeneous Bose gases

NASA Astrophysics Data System (ADS)

Beugnon, Jérôme; Navon, Nir

2017-01-01

Out-of-equilibrium phenomena are a subject of considerable interest in many fields of physics. Ultracold quantum gases, which are extremely clean, well-isolated and highly controllable systems, offer ideal platforms to investigate this topic. The recent progress in tailoring trapping potentials now allows the experimental production of homogeneous samples in custom geometries, which is a key advance for studies of the emergence of coherence in interacting quantum systems. Here we review recent experiments in which temperature quenches have been performed across the Bose-Einstein condensation phase transition in an annular geometry and in homogeneous 3D and quasi-2D gases. Combined, these experiments comprehensively explore and validate the Kibble-Zurek (KZ) scenario through complementary measurements of correlation functions and density of topological defects. They allow the measurement of KZ scaling laws, the direct confirmation of the ‘freeze-out’ hypothesis that underlies the KZ theory, and the extraction of critical exponents of the Bose-Einstein condensation transition.

Global thermodynamics of confined inhomogeneous dilute gases: A semi-classical approach

NASA Astrophysics Data System (ADS)

Poveda-Cuevas, F. J.; Reyes-Ayala, I.; Seman, J. A.; Romero-Rochín, V.

2018-04-01

In this work we present our contribution to the Latin American School of Physics "Marcos Moshinsky" 2017 on Quantum Correlations which was held in Mexico City during the summer of 2017. We review the efforts that have been done to construct a global thermodynamic description of ultracold dilute gases confined in inhomogeneous potentials. This is difficult because the presence of this non-uniform trap makes the pressure of the gas to be a spatially dependent variable and its volume an ambiguously defined quantity. In this paper we introduce new global thermodynamic variables, equivalent to pressure and volume, and propose a realistic model of the equation of state of the system. This model is based on a mean-field approach which asymptotically reaches the Thomas-Fermi limit for a weakly interacting Bose gas. We put special emphasis to the transition between the normal and superfluid phases by studying the behavior of the isothermal compressibility across the transition. We reveal how the potential modifies the critical properties of the transition by determining the critical exponents associated to the divergences not of the susceptibilities but of their derivatives.

Formation of molecules in an expanding Bose-Einstein condensate

NASA Astrophysics Data System (ADS)

Yurovsky, Vladimir; Ben-Reuven, Abraham

2004-05-01

A mean field theory [1] is extended to an inhomogeneous case of expanding hybrid atom-molecule Bose-Einstein condensates. This theory is applied to the recent MPI experiments [2] on ^87Rb demonstrating the formation of ultracold molecules due to Feshbach resonance. The subsequent dissociation of the molecules is treated using a non-mean-field parametric approximation [3]. The latter method is also used in determining optimal conditions for the formation of molecular BEC. [1] V. A. Yurovsky, A. Ben-Reuven, P. S. Julienne and C. J. Williams, Phys. Rev. A 60, R765 (1999); Phys. Rev. A 62, 043605 (2000). [2] S. Dürr, T. Volz, A. Marte, and G. Rempe, Phys. Rev. Lett. 92, 020406 (2004). [3] V. A. Yurovsky and A. Ben-Reuven, Phys. Rev. A 67, 043611 (2003).

Atomic Bose-Hubbard Systems with Single-Particle Control

NASA Astrophysics Data System (ADS)

Preiss, Philipp Moritz

Experiments with ultracold atoms in optical lattices provide outstanding opportunities to realize exotic quantum states due to a high degree of tunability and control. In this thesis, I present experiments that extend this control from global parameters to the level of individual particles. Using a quantum gas microscope for 87Rb, we have developed a single-site addressing scheme based on digital amplitude holograms. The system self-corrects for aberrations in the imaging setup and creates arbitrary beam profiles. We are thus able to shape optical potentials on the scale of single lattice sites and control the dynamics of individual atoms. We study the role of quantum statistics and interactions in the Bose-Hubbard model on the fundamental level of two particles. Bosonic quantum statistics are apparent in the Hong-Ou-Mandel interference of massive particles, which we observe in tailored double-well potentials. These underlying statistics, in combination with tunable repulsive interactions, dominate the dynamics in single- and two-particle quantum walks. We observe highly coherent position-space Bloch oscillations, bosonic bunching in Hanbury Brown-Twiss interference and the fermionization of strongly interacting bosons. Many-body states of indistinguishable quantum particles are characterized by large-scale spatial entanglement, which is difficult to detect in itinerant systems. Here, we extend the concept of Hong-Ou-Mandel interference from individual particles to many-body states to directly quantify entanglement entropy. We perform collective measurements on two copies of a quantum state and detect entanglement entropy through many-body interference. We measure the second order Renyi entropy in small Bose-Hubbard systems and detect the buildup of spatial entanglement across the superfluid-insulator transition. Our experiments open new opportunities for the single-particle-resolved preparation and characterization of many-body quantum states.

Observations of density fluctuations in an elongated Bose gas: ideal gas and quasicondensate regimes.

PubMed

Esteve, J; Trebbia, J-B; Schumm, T; Aspect, A; Westbrook, C I; Bouchoule, I

2006-04-07

We report in situ measurements of density fluctuations in a quasi-one-dimensional 87Rb Bose gas at thermal equilibrium in an elongated harmonic trap. We observe an excess of fluctuations compared to the shot-noise level expected for uncorrelated atoms. At low atomic density, the measured excess is in good agreement with the expected "bunching" for an ideal Bose gas. At high density, the measured fluctuations are strongly reduced compared to the ideal gas case. We attribute this reduction to repulsive interatomic interactions. The data are compared with a calculation for an interacting Bose gas in the quasicondensate regime.

Solving Coupled Gross--Pitaevskii Equations on a Cluster of PlayStation 3 Computers

NASA Astrophysics Data System (ADS)

Edwards, Mark; Heward, Jeffrey; Clark, C. W.

2009-05-01

At Georgia Southern University we have constructed an 8+1--node cluster of Sony PlayStation 3 (PS3) computers with the intention of using this computing resource to solve problems related to the behavior of ultra--cold atoms in general with a particular emphasis on studying bose--bose and bose--fermi mixtures confined in optical lattices. As a first project that uses this computing resource, we have implemented a parallel solver of the coupled time--dependent, one--dimensional Gross--Pitaevskii (TDGP) equations. These equations govern the behavior of dual-- species bosonic mixtures. We chose the split--operator/FFT to solve the coupled 1D TDGP equations. The fast Fourier transform component of this solver can be readily parallelized on the PS3 cpu known as the Cell Broadband Engine (CellBE). Each CellBE chip contains a single 64--bit PowerPC Processor Element known as the PPE and eight ``Synergistic Processor Element'' identified as the SPE's. We report on this algorithm and compare its performance to a non--parallel solver as applied to modeling evaporative cooling in dual--species bosonic mixtures.

Collective emission of matter-wave jets from driven Bose-Einstein condensates.

PubMed

Clark, Logan W; Gaj, Anita; Feng, Lei; Chin, Cheng

2017-11-16

Scattering is used to probe matter and its interactions in all areas of physics. In ultracold atomic gases, control over pairwise interactions enables us to investigate scattering in quantum many-body systems. Previous experiments on colliding Bose-Einstein condensates have revealed matter-wave interference, haloes of scattered atoms, four-wave mixing and correlations between counter-propagating pairs. However, a regime with strong stimulation of spontaneous collisions analogous to superradiance has proved elusive. In this regime, the collisions rapidly produce highly correlated states with macroscopic population. Here we find that runaway stimulated collisions in Bose-Einstein condensates with periodically modulated interaction strength cause the collective emission of matter-wave jets that resemble fireworks. Jets appear only above a threshold modulation amplitude and their correlations are invariant even when the number of ejected atoms grows exponentially. Hence, we show that the structures and atom occupancies of the jets stem from the quantum fluctuations of the condensate. Our findings demonstrate the conditions required for runaway stimulated collisions and reveal the quantum nature of matter-wave emission.

Time-reversal-invariant spin-orbit-coupled bilayer Bose-Einstein condensates

NASA Astrophysics Data System (ADS)

Maisberger, Matthew; Wang, Lin-Cheng; Sun, Kuei; Xu, Yong; Zhang, Chuanwei

2018-05-01

Time-reversal invariance plays a crucial role for many exotic quantum phases, particularly for topologically nontrivial states, in spin-orbit coupled electronic systems. Recently realized spin-orbit coupled cold-atom systems, however, lack the time-reversal symmetry due to the inevitable presence of an effective transverse Zeeman field. We address this issue by analyzing a realistic scheme to preserve time-reversal symmetry in spin-orbit-coupled ultracold atoms, with the use of Hermite-Gaussian-laser-induced Raman transitions that preserve spin-layer time-reversal symmetry. We find that the system's quantum states form Kramers pairs, resulting in symmetry-protected gap closing of the lowest two bands at arbitrarily large Raman coupling. We also show that Bose gases in this setup exhibit interaction-induced layer-stripe and uniform phases as well as intriguing spin-layer symmetry and spin-layer correlation.

Non-destructive imaging of spinor Bose-Einstein condensates

NASA Astrophysics Data System (ADS)

Samson, E.; Vinit, Anshuman; Raman, Chandra

2013-05-01

We present a non-destructive differential imaging technique that enables the observation of the spatial distribution of the magnetization in a spinor Bose-Einstein condensate (BEC) through a Faraday rotation protocol. In our procedure, we utilize a linearly polarized, far-detuned laser beam as our imaging probe, and upon interaction with the condensate, the beam's polarization direction undergoes Faraday rotation. A differential measurement of the orthogonal polarization components of the rotated beam provides a spatial map of the net magnetization density within the BEC. The non-destructive aspect of this method allows for continuous imaging of the condensate. This imaging technique will prove useful in experimental BEC studies, such as spatially resolved magnetometry using ultracold atoms, and non-destructive imaging of non-equilibrium behavior of antiferromagnetic spinor condensates. This work was supported by the DARPA QuASAR program through a grant from ARO.

Quantum gas-liquid condensation in an attractive Bose gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koh, Shun-ichiro

Gas-liquid condensation (GLC) in an attractive Bose gas is studied on the basis of statistical mechanics. Using some results in combinatorial mathematics, the following are derived. (1) With decreasing temperature, the Bose-statistical coherence grows in the many-body wave function, which gives rise to the divergence of the grand partition function prior to Bose-Einstein condensation. It is a quantum-mechanical analogue to the GLC in a classical gas (quantum GLC). (2) This GLC is triggered by the bosons with zero momentum. Compared with the classical GLC, an incomparably weaker attractive force creates it. For the system showing the quantum GLC, we discussmore » a cold helium 4 gas at sufficiently low pressure.« less

Pseudogap temperature and effects of a harmonic trap in the BCS-BEC crossover regime of an ultracold Fermi gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsuchiya, Shunji; Research and Education Center for Natural Sciences, Keio University, 4-1-1 Hiyoshi, Kanagawa 223-8521; CREST

2011-10-15

We theoretically investigate excitation properties in the pseudogap regime of a trapped Fermi gas. Using a combined T-matrix theory with the local density approximation, we calculate strong-coupling corrections to single-particle local density of states (LDOS), as well as the single-particle local spectral weight (LSW). Starting from the superfluid phase transition temperature T{sub c}, we clarify how the pseudogap structures in these quantities disappear with increasing the temperature. As in the case of a uniform Fermi gas, LDOS and LSW give different pseudogap temperatures T{sup *} and T{sup **} at which the pseudogap structures in these quantities completely disappear. Determining T{supmore » *} and T{sup **} over the entire BCS (Bardeen-Cooper-Schrieffer)-BEC (Bose-Einstein condensation) crossover region, we identify the pseudogap regime in the phase diagram with respect to the temperature and the interaction strength. We also show that the so-called back-bending peak recently observed in the photoemission spectra by the JILA group may be explained as an effect of pseudogap phenomenon in the trap center. Since strong pairing fluctuations, spatial inhomogeneity, and finite temperatures are important keys in considering real cold Fermi gases, our results would be useful for clarifying normal-state properties of this strongly interacting Fermi system.« less

Interactions of Ultracold Impurity Particles with Bose-Einstein Condensates

DTIC Science & Technology

2015-06-23

Lukin et al ., Phys. Rev. Lett. 87, 037901 (2001). [2] D. Jaksch et al ., Phys. Rev. Lett. 85, 2208 (2000). [3] L. Isenhower et al ., Phys. Rev. Lett...104, 010503 (2010). [4] T. Wilk et al ., Phys. Rev. Lett. 104, 010502 (2010). [5] I. Mourachko et al ., Phys. Rev. Lett. 80, 253 (1998). [6] W. R...Phys. 12, 103044 (2010). [12] R. M. W. van Bijnen et al ., J. Phys. B 44, 184008 (2011). [13] I. Lesanovsky, Phys. Rev. Lett. 106, 025301 (2011). [14] E

A quantum trampoline for ultra-cold atoms

NASA Astrophysics Data System (ADS)

Robert-de-Saint-Vincent, M.; Brantut, J.-P.; Bordé, Ch. J.; Aspect, A.; Bourdel, T.; Bouyer, P.

2010-01-01

We have observed the interferometric suspension of a free-falling Bose-Einstein condensate periodically submitted to multiple-order diffraction by a vertical 1D standing wave. This scheme permits simultaneously the compensation of gravity and coherent splitting/recombination of the matter waves. It results in high-contrast interference in the number of atoms detected at constant height. For long suspension times, multiple-wave interference is revealed through a sharpening of the fringes. We characterize our atom interferometer and use it to measure the acceleration of gravity.

Quantum phase transition modulation in an atomtronic Mott switch

NASA Astrophysics Data System (ADS)

McLain, Marie A.; Carr, Lincoln D.

2018-07-01

Mott insulators provide stable quantum states and long coherence times due to small number fluctuations, making them good candidates for quantum memory and atomic circuits. We propose a proof-of-principle for a 1D Mott switch using an ultracold Bose gas and optical lattice. With time-evolving block decimation simulations—efficient matrix product state methods—we design a means for transient parameter characterization via a local excitation for ease of engineering into more complex atomtronics. We perform the switch operation by tuning the intensity of the optical lattice, and thus the interaction strength through a conductance transition due to the confined modifications of the ‘wedding cake’ Mott structure. We demonstrate the time-dependence of Fock state transmission and fidelity of the excitation as a means of tuning up the device in a double well and as a measure of noise performance. Two-point correlations via the g (2) measure provide additional information regarding superfluid fragments on the Mott insulating background due to the confinement of the potential.

Diffusion Monte Carlo study of strongly interacting two-dimensional Fermi gases

DOE PAGES

Galea, Alexander; Dawkins, Hillary; Gandolfi, Stefano; ...

2016-02-01

Ultracold atomic Fermi gases have been a popular topic of research, with attention being paid recently to two-dimensional (2D) gases. In this work, we perform T=0 ab initio diffusion Monte Carlo calculations for a strongly interacting two-component Fermi gas confined to two dimensions. We first go over finite-size systems and the connection to the thermodynamic limit. After that, we illustrate pertinent 2D scattering physics and properties of the wave function. We then show energy results for the strong-coupling crossover, in between the Bose-Einstein condensation (BEC) and Bardeen-Cooper-Schrieffer (BCS) regimes. Our energy results for the BEC-BCS crossover are parametrized to producemore » an equation of state, which is used to determine Tan's contact. We carry out a detailed comparison with other microscopic results. Lastly, we calculate the pairing gap for a range of interaction strengths in the strong coupling regime, following from variationally optimized many-body wave functions.« less

Two Impurities in a Bose-Einstein Condensate: From Yukawa to Efimov Attracted Polarons

NASA Astrophysics Data System (ADS)

Naidon, Pascal

2018-04-01

The well-known Yukawa and Efimov potentials are two different mediated interaction potentials. The first one arises in quantum field theory from the exchange of virtual particles. The second one is mediated by a real particle resonantly interacting with two other particles. This Letter shows how two impurities immersed in a Bose-Einstein condensate can exhibit both phenomena. For a weak attraction with the condensate, the two impurities form two polarons that interact through a weak Yukawa attraction mediated by virtual excitations. For a resonant attraction with the condensate, the exchanged excitation becomes a real boson and the mediated interaction changes to a strong Efimov attraction that can bind the two polarons. The resulting bipolarons turn into in-medium Efimov trimers made of the two impurities and one boson. Evidence of this physics could be seen in ultracold mixtures of atoms.

Atom loss resonances in a Bose-Einstein condensate.

PubMed

Langmack, Christian; Smith, D Hudson; Braaten, Eric

2013-07-12

Atom loss resonances in ultracold trapped atoms have been observed at scattering lengths near atom-dimer resonances, at which Efimov trimers cross the atom-dimer threshold, and near two-dimer resonances, at which universal tetramers cross the dimer-dimer threshold. We propose a new mechanism for these loss resonances in a Bose-Einstein condensate of atoms. As the scattering length is ramped to the large final value at which the atom loss rate is measured, the time-dependent scattering length generates a small condensate of shallow dimers coherently from the atom condensate. The coexisting atom and dimer condensates can be described by a low-energy effective field theory with universal coefficients that are determined by matching exact results from few-body physics. The classical field equations for the atom and dimer condensates predict narrow enhancements in the atom loss rate near atom-dimer resonances and near two-dimer resonances due to inelastic dimer collisions.

Searching for Supersolidity in Ultracold Atomic Bose Condensates with Rashba Spin-Orbit Coupling

NASA Astrophysics Data System (ADS)

Liao, Renyuan

2018-04-01

We developed a functional integral formulation for the stripe phase of spinor Bose-Einstein condensates with Rashba spin-orbit coupling. The excitation spectrum is found to exhibit double gapless band structures, identified to be two Goldstone modes resulting from spontaneously broken internal gauge symmetry and translational invariance symmetry. The sound velocities display anisotropic behavior with the lower branch vanishing in the direction perpendicular to the stripe in the x -y plane. At the transition point between the plane-wave phase and the stripe phase, physical quantities such as fluctuation correction to the ground-state energy and quantum depletion of the condensates exhibit discontinuity, characteristic of the first-order phase transition. Despite strong quantum fluctuations induced by Rashba spin-orbit coupling, we show that the supersolid phase is stable against quantum depletion. Finally, we extend our formulation to finite temperatures to account for interactions between excitations.

Herbert P. Broida Prize Talk: A single Rydberg electron in a Bose-Einstein condensate: from two to few to many-body physics

NASA Astrophysics Data System (ADS)

Pfau, Tilman

2017-04-01

Modern quantum scattering theory was developed in the context of Rydberg spectroscopy in 1934 by Enrico Fermi. He showed that for slow electrons the scattering from polarizable atoms via a 1/r4 potential is purely s-wave and can be described by a Fermi pseudopotential and a scattering length. To study this interaction Rydberg electrons are well suited as they are slow and trapped by the charged nucleus. In a high pressure discharge Amaldi and Segre, observed a line shift proportional to the scattering length. At ultracold temperatures one can ask the opposite question: What does a Rydberg electron do to the neutral atom sitting in the electronic orbit? We found that one, two or many ground state atoms can be trapped in the mean-field potential created by the Rydberg electron, leading to so called ultra-long range Rydberg molecules. I will explain this novel molecular binding mechanism and the properties of these exotic molecules. At higher Rydberg states the spatial extent of the Rydberg electron orbit is increasing. For principal quantum numbers n in the range of 100-200 up to several ten thousand ultracold ground state atoms can be located inside one Rydberg atom, When we excite a single Rydberg electron in a Bose-Einstein Condensate, the orbital size of which becomes comparable to the size of the BEC we observe the coupling between the electron and phonons in the BEC.

Bose-Einstein condensation in the relativistic ideal Bose gas.

PubMed

Grether, M; de Llano, M; Baker, George A

2007-11-16

The Bose-Einstein condensation (BEC) critical temperature in a relativistic ideal Bose gas of identical bosons, with and without the antibosons expected to be pair-produced abundantly at sufficiently hot temperatures, is exactly calculated for all boson number densities, all boson point rest masses, and all temperatures. The Helmholtz free energy at the critical BEC temperature is lower with antibosons, thus implying that omitting antibosons always leads to the computation of a metastable state.

Bose-Einstein condensation on a manifold with non-negative Ricci curvature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Akant, Levent, E-mail: levent.akant@boun.edu.tr; Ertuğrul, Emine, E-mail: emine.ertugrul@boun.edu.tr; Tapramaz, Ferzan, E-mail: waskhez@gmail.com

The Bose-Einstein condensation for an ideal Bose gas and for a dilute weakly interacting Bose gas in a manifold with non-negative Ricci curvature is investigated using the heat kernel and eigenvalue estimates of the Laplace operator. The main focus is on the nonrelativistic gas. However, special relativistic ideal gas is also discussed. The thermodynamic limit of the heat kernel and eigenvalue estimates is taken and the results are used to derive bounds for the depletion coefficient. In the case of a weakly interacting gas, Bogoliubov approximation is employed. The ground state is analyzed using heat kernel methods and finite sizemore » effects on the ground state energy are proposed. The justification of the c-number substitution on a manifold is given.« less

Bose-Einstein condensation of paraxial light

NASA Astrophysics Data System (ADS)

Klaers, J.; Schmitt, J.; Damm, T.; Vewinger, F.; Weitz, M.

2011-10-01

Photons, due to the virtually vanishing photon-photon interaction, constitute to very good approximation an ideal Bose gas, but owing to the vanishing chemical potential a (free) photon gas does not show Bose-Einstein condensation. However, this is not necessarily true for a lower-dimensional photon gas. By means of a fluorescence induced thermalization process in an optical microcavity one can achieve a thermal photon gas with freely adjustable chemical potential. Experimentally, we have observed thermalization and subsequently Bose-Einstein condensation of the photon gas at room temperature. In this paper, we give a detailed description of the experiment, which is based on a dye-filled optical microcavity, acting as a white-wall box for photons. Thermalization is achieved in a photon number-conserving way by photon scattering off the dye molecules, and the cavity mirrors both provide an effective photon mass and a confining potential-key prerequisites for the Bose-Einstein condensation of photons. The experimental results are in good agreement with both a statistical and a simple rate equation model, describing the properties of the thermalized photon gas.

Dipole-dipole interactions in a hot atomic vapor and in an ultracold gas of Rydberg atoms

NASA Astrophysics Data System (ADS)

Sautenkov, V. A.; Saakyan, S. A.; Bronin, S. Ya; Klyarfeld, A. B.; Zelener, B. B.; Zelener, B. V.

2018-01-01

In our paper ideal and non-ideal gas media of neutral atoms are analyzed. The first we discuss a dipole broadening of atomic transitions in excited dilute and dense metal vapors. Then the theoretical studies of the dipole-dipole interactions in dense ultracold gas of Rydberg atoms are considered. Possible future experiments on a base of our experimental arrangement are suggested.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: On the gravitational-deceleration initiation of the phase transition of gas to a Bose condensate

NASA Astrophysics Data System (ADS)

Rivlin, L. A.

2008-01-01

A scenario of the experiment on the observation of the isothermal Bose condensation of cooled gas with increasing the concentration of atoms caused by the deceleration of a vertical atomic beam in the gravitational field resulting in a decrease in the phase transition critical temperature below the gas temperature is considered. Coherent phenomena accompanying the evolution of the Bose condensate during further beam deceleration are pointed out.

Satyendranath Bose: Co-Founder of Quantum Statistics

ERIC Educational Resources Information Center

Blanpied, William A.

1972-01-01

Satyendranath Bose was first to prove Planck's Law by using ideal quantum gas. Einstein credited Bose for this first step in the development of quantum statistical mechanics. Bose did not realize the importance of his work, perhaps because of peculiar academic settings in India under British rule. (PS)

Vortex rings in Bose gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belyaev, S. T., E-mail: bst@kiae.ru

2016-06-15

We consider excitations that exist, in addition to phonons, in the ideal Bose gas at zero temperature. These excitations are vortex rings whose energy spectrum is similar to the roton one in liquid helium.

Off-equilibrium infrared structure of self-interacting scalar fields: Universal scaling, vortex-antivortex superfluid dynamics, and Bose-Einstein condensation

NASA Astrophysics Data System (ADS)

Deng, Jian; Schlichting, Soeren; Venugopalan, Raju; Wang, Qun

2018-05-01

We map the infrared dynamics of a relativistic single-component (N =1 ) interacting scalar field theory to that of nonrelativistic complex scalar fields. The Gross-Pitaevskii (GP) equation, describing the real-time dynamics of single-component ultracold Bose gases, is obtained at first nontrivial order in an expansion proportional to the powers of λ ϕ2/m2 where λ , ϕ , and m are the coupling constant, the scalar field, and the particle mass respectively. Our analytical studies are corroborated by numerical simulations of the spatial and momentum structure of overoccupied scalar fields in (2+1)-dimensions. Universal scaling of infrared modes, vortex-antivortex superfluid dynamics, and the off-equilibrium formation of a Bose-Einstein condensate are observed. Our results for the universal scaling exponents are in agreement with those extracted in the numerical simulations of the GP equation. As in these simulations, we observe coarsening phase kinetics in the Bose superfluid with strongly anomalous scaling exponents relative to that of vertex resummed kinetic theory. Our relativistic field theory framework further allows one to study more closely the coupling between superfluid and normal fluid modes, specifically the turbulent momentum and spatial structure of the coupling between a quasiparticle cascade to the infrared and an energy cascade to the ultraviolet. We outline possible applications of the formalism to the dynamics of vortex-antivortex formation and to the off-equilibrium dynamics of the strongly interacting matter formed in heavy-ion collisions.

Contact interaction in an unitary ultracold Fermi gas

DOE PAGES

Pessoa, Renato; Gandolfi, Stefano; Vitiello, S. A.; ...

2015-12-16

An ultracold Fermi atomic gas at unitarity presents universal properties that in the dilute limit can be well described by a contact interaction. By employing a guiding function with correct boundary conditions and making simple modifications to the sampling procedure we are able to calculate the properties of a true contact interaction with the diffusion Monte Carlo method. The results are obtained with small variances. Our calculations for the Bertsch and contact parameters are in excellent agreement with published experiments. The possibility of using a more faithful description of ultracold atomic gases can help uncover additional features of ultracold atomicmore » gases. In addition, this work paves the way to perform quantum Monte Carlo calculations for other systems interacting with contact interactions, where the description using potentials with finite effective range might not be accurate.« less

Quantum chaos in ultracold collisions of gas-phase erbium atoms.

PubMed

Frisch, Albert; Mark, Michael; Aikawa, Kiyotaka; Ferlaino, Francesca; Bohn, John L; Makrides, Constantinos; Petrov, Alexander; Kotochigova, Svetlana

2014-03-27

Atomic and molecular samples reduced to temperatures below one microkelvin, yet still in the gas phase, afford unprecedented energy resolution in probing and manipulating the interactions between their constituent particles. As a result of this resolution, atoms can be made to scatter resonantly on demand, through the precise control of a magnetic field. For simple atoms, such as alkalis, scattering resonances are extremely well characterized. However, ultracold physics is now poised to enter a new regime, where much more complex species can be cooled and studied, including magnetic lanthanide atoms and even molecules. For molecules, it has been speculated that a dense set of resonances in ultracold collision cross-sections will probably exhibit essentially random fluctuations, much as the observed energy spectra of nuclear scattering do. According to the Bohigas-Giannoni-Schmit conjecture, such fluctuations would imply chaotic dynamics of the underlying classical motion driving the collision. This would necessitate new ways of looking at the fundamental interactions in ultracold atomic and molecular systems, as well as perhaps new chaos-driven states of ultracold matter. Here we describe the experimental demonstration that random spectra are indeed found at ultralow temperatures. In the experiment, an ultracold gas of erbium atoms is shown to exhibit many Fano-Feshbach resonances, of the order of three per gauss for bosons. Analysis of their statistics verifies that their distribution of nearest-neighbour spacings is what one would expect from random matrix theory. The density and statistics of these resonances are explained by fully quantum mechanical scattering calculations that locate their origin in the anisotropy of the atoms' potential energy surface. Our results therefore reveal chaotic behaviour in the native interaction between ultracold atoms.

Investigation of Bose Condensation in Ideal Bose Gas Trapped under Generic Power Law Potential in d Dimension

NASA Astrophysics Data System (ADS)

Mehedi Faruk, Mir; Sazzad Hossain, Md.; Muktadir Rahman, Md.

2016-02-01

The changes in characteristics of Bose condensation of ideal Bose gas due to an external generic power law potential U=\\sumi=1dci\\vert xi/ai\\vertni are studied carefully. Detailed calculation of Kim et al. (J. Phys. Condens. Matter 11 (1999) 10269) yielded the hierarchy of condensation transitions with changing fractional dimensionality. In this manuscript, some theorems regarding specific heat at constant volume CV are presented. Careful examination of these theorems reveal the existence of hidden hierarchy of the condensation transition in trapped systems as well.

Kolmogorov Turbulence Defeated by Anderson Localization for a Bose-Einstein Condensate in a Sinai-Oscillator Trap

NASA Astrophysics Data System (ADS)

Ermann, Leonardo; Vergini, Eduardo; Shepelyansky, Dima L.

2017-08-01

We study the dynamics of a Bose-Einstein condensate in a Sinai-oscillator trap under a monochromatic driving force. Such a trap is formed by a harmonic potential and a repulsive disk located in the center vicinity corresponding to the first experiments of condensate formation by Ketterle and co-workers in 1995. We allow that the external driving allows us to model the regime of weak wave turbulence with the Kolmogorov energy flow from low to high energies. We show that in a certain regime of weak driving and weak nonlinearity such a turbulent energy flow is defeated by the Anderson localization that leads to localization of energy on low energy modes. This is in a drastic contrast to the random phase approximation leading to energy flow to high modes. A critical threshold is determined above which the turbulent flow to high energies becomes possible. We argue that this phenomenon can be studied with ultracold atoms in magneto-optical traps.

Blue-detuned optical ring trap for Bose-Einstein condensates based on conical refraction.

PubMed

Turpin, A; Polo, J; Loiko, Yu V; Küber, J; Schmaltz, F; Kalkandjiev, T K; Ahufinger, V; Birkl, G; Mompart, J

2015-01-26

We present a novel approach for the optical manipulation of neutral atoms in annular light structures produced by the phenomenon of conical refraction occurring in biaxial optical crystals. For a beam focused to a plane behind the crystal, the focal plane exhibits two concentric bright rings enclosing a ring of null intensity called the Poggendorff ring. We demonstrate both theoretically and experimentally that the Poggendorff dark ring of conical refraction is confined in three dimensions by regions of higher intensity. We derive the positions of the confining intensity maxima and minima and discuss the application of the Poggendorff ring for trapping ultra-cold atoms using the repulsive dipole force of blue-detuned light. We give analytical expressions for the trapping frequencies and potential depths along both the radial and the axial directions. Finally, we present realistic numerical simulations of the dynamics of a ⁸⁷Rb Bose-Einstein condensate trapped inside the Poggendorff ring which are in good agreement with corresponding experimental results.

Kolmogorov Turbulence Defeated by Anderson Localization for a Bose-Einstein Condensate in a Sinai-Oscillator Trap.

PubMed

Ermann, Leonardo; Vergini, Eduardo; Shepelyansky, Dima L

2017-08-04

We study the dynamics of a Bose-Einstein condensate in a Sinai-oscillator trap under a monochromatic driving force. Such a trap is formed by a harmonic potential and a repulsive disk located in the center vicinity corresponding to the first experiments of condensate formation by Ketterle and co-workers in 1995. We allow that the external driving allows us to model the regime of weak wave turbulence with the Kolmogorov energy flow from low to high energies. We show that in a certain regime of weak driving and weak nonlinearity such a turbulent energy flow is defeated by the Anderson localization that leads to localization of energy on low energy modes. This is in a drastic contrast to the random phase approximation leading to energy flow to high modes. A critical threshold is determined above which the turbulent flow to high energies becomes possible. We argue that this phenomenon can be studied with ultracold atoms in magneto-optical traps.

Tunable Spin-orbit Coupling and Quantum Phase Transition in a Trapped Bose-Einstein Condensate

PubMed Central

Zhang, Yongping; Chen, Gang; Zhang, Chuanwei

2013-01-01

Spin-orbit coupling (SOC), the intrinsic interaction between a particle spin and its motion, is responsible for various important phenomena, ranging from atomic fine structure to topological condensed matter physics. The recent experimental breakthrough on the realization of SOC for ultra-cold atoms provides a completely new platform for exploring spin-orbit coupled superfluid physics. However, the SOC strength in the experiment is not tunable. In this report, we propose a scheme for tuning the SOC strength through a fast and coherent modulation of the laser intensities. We show that the many-body interaction between atoms, together with the tunable SOC, can drive a quantum phase transition (QPT) from spin-balanced to spin-polarized ground states in a harmonic trapped Bose-Einstein condensate (BEC), which resembles the long-sought Dicke QPT. We characterize the QPT using the periods of collective oscillations of the BEC, which show pronounced peaks and damping around the quantum critical point. PMID:23727689

Observation of the Mott insulator to superfluid crossover of a driven-dissipative Bose-Hubbard system

PubMed Central

Tomita, Takafumi; Nakajima, Shuta; Danshita, Ippei; Takasu, Yosuke; Takahashi, Yoshiro

2017-01-01

Dissipation is ubiquitous in nature and plays a crucial role in quantum systems such as causing decoherence of quantum states. Recently, much attention has been paid to an intriguing possibility of dissipation as an efficient tool for the preparation and manipulation of quantum states. We report the realization of successful demonstration of a novel role of dissipation in a quantum phase transition using cold atoms. We realize an engineered dissipative Bose-Hubbard system by introducing a controllable strength of two-body inelastic collision via photoassociation for ultracold bosons in a three-dimensional optical lattice. In the dynamics subjected to a slow ramp-down of the optical lattice, we find that strong on-site dissipation favors the Mott insulating state: The melting of the Mott insulator is delayed, and the growth of the phase coherence is suppressed. The controllability of the dissipation is highlighted by quenching the dissipation, providing a novel method for investigating a quantum many-body state and its nonequilibrium dynamics. PMID:29291246

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mazzarella, G.; Toigo, F.; Salasnich, L.

We consider a bosonic Josephson junction made of N ultracold and dilute atoms confined by a quasi-one-dimensional double-well potential within the two-site Bose-Hubbard model framework. The behavior of the system is investigated at zero temperature by varying the interatomic interaction from the strongly attractive regime to the repulsive one. We show that the ground state exhibits a crossover from a macroscopic Schroedinger-cat state to a separable Fock state through an atomic coherent regime. By diagonalizing the Bose-Hubbard Hamiltonian we characterize the emergence of the macroscopic cat states by calculating the Fisher information F, the coherence by means of the visibilitymore » {alpha} of the interference fringes in the momentum distribution, and the quantum correlations by using the entanglement entropy S. Both Fisher information and visibility are shown to be related to the ground-state energy by employing the Hellmann-Feynman theorem. This result, together with a perturbative calculation of the ground-state energy, allows simple analytical formulas for F and {alpha} to be obtained over a range of interactions, in excellent agreement with the exact diagonalization of the Bose-Hubbard Hamiltonian. In the attractive regime the entanglement entropy attains values very close to its upper limit for a specific interaction strength lying in the region where coherence is lost and self-trapping sets in.« less

Atomic quantum simulation of dynamical gauge fields coupled to fermionic matter: from string breaking to evolution after a quench.

PubMed

Banerjee, D; Dalmonte, M; Müller, M; Rico, E; Stebler, P; Wiese, U-J; Zoller, P

2012-10-26

Using a Fermi-Bose mixture of ultracold atoms in an optical lattice, we construct a quantum simulator for a U(1) gauge theory coupled to fermionic matter. The construction is based on quantum links which realize continuous gauge symmetry with discrete quantum variables. At low energies, quantum link models with staggered fermions emerge from a Hubbard-type model which can be quantum simulated. This allows us to investigate string breaking as well as the real-time evolution after a quench in gauge theories, which are inaccessible to classical simulation methods.

Rigorous investigation of the reduced density matrix for the ideal Bose gas in harmonic traps by a loop-gas-like approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beau, Mathieu, E-mail: mbeau@stp.dias.ie; Savoie, Baptiste, E-mail: baptiste.savoie@gmail.com

2014-05-15

In this paper, we rigorously investigate the reduced density matrix (RDM) associated to the ideal Bose gas in harmonic traps. We present a method based on a sum-decomposition of the RDM allowing to treat not only the isotropic trap, but also general anisotropic traps. When focusing on the isotropic trap, the method is analogous to the loop-gas approach developed by Mullin [“The loop-gas approach to Bose-Einstein condensation for trapped particles,” Am. J. Phys. 68(2), 120 (2000)]. Turning to the case of anisotropic traps, we examine the RDM for some anisotropic trap models corresponding to some quasi-1D and quasi-2D regimes. Formore » such models, we bring out an additional contribution in the local density of particles which arises from the mesoscopic loops. The close connection with the occurrence of generalized-Bose-Einstein condensation is discussed. Our loop-gas-like approach provides relevant information which can help guide numerical investigations on highly anisotropic systems based on the Path Integral Monte Carlo method.« less

Thermometry of ultracold atoms by electromagnetically induced transparency

NASA Astrophysics Data System (ADS)

Peters, Thorsten; Wittrock, Benjamin; Blatt, Frank; Halfmann, Thomas; Yatsenko, Leonid P.

2012-06-01

We report on systematic numerical and experimental investigations of electromagnetically induced transparency (EIT) to determine temperatures in an ultracold atomic gas. The technique relies on the strong dependence of EIT on atomic motion (i.e., Doppler shifts), when the relevant atomic transitions are driven with counterpropagating probe and control laser beams. Electromagnetically induced transparency permits thermometry with satisfactory precision over a large temperature range, which can be addressed by the appropriate choice of Rabi frequency in the control beam. In contrast to time-of-flight techniques, thermometry by EIT is fast and nondestructive, i.e., essentially it does not affect the ultracold medium. In an experimental demonstration we apply both EIT and time-of-flight measurements to determine temperatures along different symmetry axes of an anisotropic ultracold gas. As an interesting feature we find that the temperatures in the anisotropic atom cloud vary in different directions.

Artificial Gauge Fields for Ultracold Neutral Atoms

NASA Astrophysics Data System (ADS)

Jimenez-Garcia, Karina

2013-05-01

Ultracold atoms are a versatile probe for physics at the core of the most intriguing and fascinating systems in the quantum world. Due to the high degree of experimental control offered by such systems, effective Hamiltonians can be designed and experimentally implemented on them. This unique feature makes ultracold atom systems ideal for quantum simulation of complex phenomena as important as high-temperature superconductivity, and recently of novel artificial gauge fields. Suitably designed artificial gauge fields allow neutral particles to experience synthetic- electric or magnetic fields; furthermore, their generalization to matrix valued gauge fields leads to spin-orbit coupling featuring unprecedented control in contrast to ordinary condensed matter systems, thus allowing the characterization of the underlying mechanism of phenomena such as the spin Hall effect and topological insulators. In this talk, I will present an overview of our experiments on quantum simulation with ultracold atom systems by focusing on the realization of light induced artificial gauge fields. We illuminate our Bose-Einstein condensates with a pair of far detuned ``Raman'' lasers, thus creating dressed states that are spin and momentum superpositions. We adiabatically load the atoms into the lowest energy dressed state, where they acquire an experimentally-tunable effective dispersion relation, i.e. we introduce gauge terms into the Hamiltonian. We control such light-induced gauge terms via the strength of the Raman coupling and the detuning from Raman resonance. Our experimental techniques for ultracold bosons have surpassed the apparent limitations imposed by their neutral charge, bosonic nature, and ultra-low energy and have allowed the observation of these new and exciting phenomena. Future work might allow the realization of the bosonic quantum Hall effect, of topological insulators and of systems supporting Majorana fermions using cold atoms. This work was partially supported by the ONR; the ARO with funds from the DARPA OLE program; the Atomtronics MURI; and the NSF through the PFC at the JQI. I acknowledge the support from CONACYT.

Creation of Rydberg Polarons in a Bose Gas

NASA Astrophysics Data System (ADS)

Camargo, F.; Schmidt, R.; Whalen, J. D.; Ding, R.; Woehl, G.; Yoshida, S.; Burgdörfer, J.; Dunning, F. B.; Sadeghpour, H. R.; Demler, E.; Killian, T. C.

2018-02-01

We report spectroscopic observation of Rydberg polarons in an atomic Bose gas. Polarons are created by excitation of Rydberg atoms as impurities in a strontium Bose-Einstein condensate. They are distinguished from previously studied polarons by macroscopic occupation of bound molecular states that arise from scattering of the weakly bound Rydberg electron from ground-state atoms. The absence of a p -wave resonance in the low-energy electron-atom scattering in Sr introduces a universal behavior in the Rydberg spectral line shape and in scaling of the spectral width (narrowing) with the Rydberg principal quantum number, n . Spectral features are described with a functional determinant approach (FDA) that solves an extended Fröhlich Hamiltonian for a mobile impurity in a Bose gas. Excited states of polyatomic Rydberg molecules (trimers, tetrameters, and pentamers) are experimentally resolved and accurately reproduced with a FDA.

Ultracold Mixtures of Rubidium and Ytterbium for Open Quantum System Engineering

NASA Astrophysics Data System (ADS)

Herold, Creston David

Exquisite experimental control of quantum systems has led to sharp growth of basic quantum research in recent years. Controlling dissipation has been crucial in producing ultracold, trapped atomic samples. Recent theoretical work has suggested dissipation can be a useful tool for quantum state preparation. Controlling not only how a system interacts with a reservoir, but the ability to engineer the reservoir itself would be a powerful platform for open quantum system research. Toward this end, we have constructed an apparatus to study ultracold mixtures of rubidium (Rb) and ytterbium (Yb). We have developed a Rb-blind optical lattice at 423.018(7) nm, which will enable us to immerse a lattice of Yb atoms (the system) into a Rb BEC (superfluid reservoir). We have produced Bose-Einstein condensates of 170Yb and 174Yb, two of the five bosonic isotopes of Yb, which also has two fermionic isotopes. Flexible optical trapping of Rb and Yb was achieved with a two-color dipole trap of 532 and 1064 nm, and we observed thermalization in ultracold mixtures of Rb and Yb. Using the Rb-blind optical lattice, we measured very small light shifts of 87Rb BECs near the light shift zero-wavelengths adjacent the 6p electronic states, through a coherent series of lattice pulses. The positions of the zero-wavelengths are sensitive to the electric dipole matrix elements between the 5s and 6p states, and we made the first experimental measurement of their strength. By measuring a light shift, we were not sensitive to excited state branching ratios, and we achieved a precision better than 0.3%.

Competition between Bose-Einstein Condensation and Spin Dynamics.

PubMed

Naylor, B; Brewczyk, M; Gajda, M; Gorceix, O; Maréchal, E; Vernac, L; Laburthe-Tolra, B

2016-10-28

We study the impact of spin-exchange collisions on the dynamics of Bose-Einstein condensation by rapidly cooling a chromium multicomponent Bose gas. Despite relatively strong spin-dependent interactions, the critical temperature for Bose-Einstein condensation is reached before the spin degrees of freedom fully thermalize. The increase in density due to Bose-Einstein condensation then triggers spin dynamics, hampering the formation of condensates in spin-excited states. Small metastable spinor condensates are, nevertheless, produced, and they manifest in strong spin fluctuations.

Many-body interferometry of magnetic polaron dynamics

NASA Astrophysics Data System (ADS)

Ashida, Yuto; Schmidt, Richard; Tarruell, Leticia; Demler, Eugene

2018-02-01

The physics of quantum impurities coupled to a many-body environment is among the most important paradigms of condensed-matter physics. In particular, the formation of polarons, quasiparticles dressed by the polarization cloud, is key to the understanding of transport, optical response, and induced interactions in a variety of materials. Despite recent remarkable developments in ultracold atoms and solid-state materials, the direct measurement of their ultimate building block, the polaron cloud, has remained a fundamental challenge. We propose and analyze a platform to probe time-resolved dynamics of polaron-cloud formation with an interferometric protocol. We consider an impurity atom immersed in a two-component Bose-Einstein condensate where the impurity generates spin-wave excitations that can be directly measured by the Ramsey interference of surrounding atoms. The dressing by spin waves leads to the formation of magnetic polarons and reveals a unique interplay between few- and many-body physics that is signified by single- and multi-frequency oscillatory dynamics corresponding to the formation of many-body bound states. Finally, we discuss concrete experimental implementations in ultracold atoms.

Off-diagonal long-range order, cycle probabilities, and condensate fraction in the ideal Bose gas.

PubMed

Chevallier, Maguelonne; Krauth, Werner

2007-11-01

We discuss the relationship between the cycle probabilities in the path-integral representation of the ideal Bose gas, off-diagonal long-range order, and Bose-Einstein condensation. Starting from the Landsberg recursion relation for the canonic partition function, we use elementary considerations to show that in a box of size L3 the sum of the cycle probabilities of length k>L2 equals the off-diagonal long-range order parameter in the thermodynamic limit. For arbitrary systems of ideal bosons, the integer derivative of the cycle probabilities is related to the probability of condensing k bosons. We use this relation to derive the precise form of the pik in the thermodynamic limit. We also determine the function pik for arbitrary systems. Furthermore, we use the cycle probabilities to compute the probability distribution of the maximum-length cycles both at T=0, where the ideal Bose gas reduces to the study of random permutations, and at finite temperature. We close with comments on the cycle probabilities in interacting Bose gases.

Wave-function-renormalization effects in resonantly enhanced tunneling

NASA Astrophysics Data System (ADS)

Lörch, N.; Pepe, F. V.; Lignier, H.; Ciampini, D.; Mannella, R.; Morsch, O.; Arimondo, E.; Facchi, P.; Florio, G.; Pascazio, S.; Wimberger, S.

2012-05-01

We study the time evolution of ultracold atoms in an accelerated optical lattice. For a Bose-Einstein condensate with a narrow quasimomentum distribution in a shallow optical lattice the decay of the survival probability in the ground band has a steplike structure. In this regime we establish a connection between the wave-function-renormalization parameter Z introduced by P. Facchi, H. Nakazato, and S. Pascazio [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.86.2699 86, 2699 (2001)] to characterize nonexponential decay and the phenomenon of resonantly enhanced tunneling, where the decay rate is peaked for particular values of the lattice depth and the accelerating force.

Quantum localization and bound-state formation in Bose-Einstein condensates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Franzosi, Roberto; Giampaolo, Salvatore M.; Illuminati, Fabrizio

2010-12-15

We discuss the possibility of exponential quantum localization in systems of ultracold bosonic atoms with repulsive interactions in open optical lattices without disorder. We show that exponential localization occurs in the maximally excited state of the lowest energy band. We establish the conditions under which the presence of the upper energy bands can be neglected, determine the successive stages and the quantum phase boundaries at which localization occurs, and discuss schemes to detect it experimentally by visibility measurements. The discussed mechanism is a particular type of quantum localization that is intuitively understood in terms of the interplay between nonlinearity andmore » a bounded energy spectrum.« less

Competing bosonic condensates in optical lattice with a mixture of single and pair hoppings

NASA Astrophysics Data System (ADS)

Travin, V. M.; Kopeć, T. K.

2017-01-01

A system of ultra-cold atoms with single boson and pair tunneling of bosonic atoms is considered in an optical lattice at arbitrary temperature. A mean-field theory was applied to the extended Bose-Hubbard Hamiltonian describing the system in order to investigate the competition between superfluid and pair superfluid as a function of the chemical potential and the temperature. To this end we have applied a method based on the Laplace transform method for the efficient calculation of the statistical sum for the quantum Hamiltonian. These results may be of interest for experiments on cold atom systems in optical lattices.

Rapid prototyping of versatile atom chips for atom interferometry applications.

NASA Astrophysics Data System (ADS)

Kasch, Brian; Squires, Matthew; Olson, Spencer; Kroese, Bethany; Imhof, Eric; Kohn, Rudolph; Stuhl, Benjamin; Schramm, Stacy; Stickney, James

2016-05-01

We present recent advances in the manipulation of ultracold atoms with ex-vacuo atom chips (i.e. atom chips that are not inside to the UHV chamber). Details will be presented of an experimental system that allows direct bonded copper (DBC) atom chips to be removed and replaced in minutes, requiring minimal re-optimization of parameters. This system has been used to create Bose-Einstein condensates, as well as magnetic waveguides with precisely tunable axial parameters, allowing double wells, pure harmonic confinement, and modified harmonic traps. We investigate the effects of higher order magnetic field contributions to the waveguide, and the implications for confined atom interferometry.

Critical exponents of the disorder-driven superfluid-insulator transition in one-dimensional Bose-Einstein condensates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cestari, J. C. C.; Foerster, A.; Gusmao, M. A.

2011-11-15

We investigate the nature of the superfluid-insulator quantum phase transition driven by disorder for noninteracting ultracold atoms on one-dimensional lattices. We consider two different cases: Anderson-type disorder, with local energies randomly distributed, and pseudodisorder due to a potential incommensurate with the lattice, which is usually called the Aubry-Andre model. A scaling analysis of numerical data for the superfluid fraction for different lattice sizes allows us to determine quantum critical exponents characterizing the disorder-driven superfluid-insulator transition. We also briefly discuss the effect of interactions close to the noninteracting quantum critical point of the Aubry-Andre model.

Bose-Einstein condensation in an ultra-hot gas of pumped magnons.

PubMed

Serga, Alexander A; Tiberkevich, Vasil S; Sandweg, Christian W; Vasyuchka, Vitaliy I; Bozhko, Dmytro A; Chumak, Andrii V; Neumann, Timo; Obry, Björn; Melkov, Gennadii A; Slavin, Andrei N; Hillebrands, Burkard

2014-03-11

Bose-Einstein condensation of quasi-particles such as excitons, polaritons, magnons and photons is a fascinating quantum mechanical phenomenon. Unlike the Bose-Einstein condensation of real particles (like atoms), these processes do not require low temperatures, since the high densities of low-energy quasi-particles needed for the condensate to form can be produced via external pumping. Here we demonstrate that such a pumping can create remarkably high effective temperatures in a narrow spectral region of the lowest energy states in a magnon gas, resulting in strikingly unexpected transitional dynamics of Bose-Einstein magnon condensate: the density of the condensate increases immediately after the external magnon flow is switched off and initially decreases if it is switched on again. This behaviour finds explanation in a nonlinear 'evaporative supercooling' mechanism that couples the low-energy magnons overheated by pumping with all the other thermal magnons, removing the excess heat, and allowing Bose-Einstein condensate formation.

Virial Coefficients from Unified Statistical Thermodynamics of Quantum Gases Trapped under Generic Power Law Potential in d Dimension and Equivalence of Quantum Gases

NASA Astrophysics Data System (ADS)

Bahauddin, Shah Mohammad; Mehedi Faruk, Mir

2016-09-01

From the unified statistical thermodynamics of quantum gases, the virial coefficients of ideal Bose and Fermi gases, trapped under generic power law potential are derived systematically. From the general result of virial coefficients, one can produce the known results in d = 3 and d = 2. But more importantly we found that, the virial coefficients of Bose and Fermi gases become identical (except the second virial coefficient, where the sign is different) when the gases are trapped under harmonic potential in d = 1. This result suggests the equivalence between Bose and Fermi gases established in d = 1 (J. Stat. Phys. DOI 10.1007/s10955-015-1344-4). Also, it is found that the virial coefficients of two-dimensional free Bose (Fermi) gas are equal to the virial coefficients of one-dimensional harmonically trapped Bose (Fermi) gas.

Superfluid drag in the two-component Bose-Hubbard model

NASA Astrophysics Data System (ADS)

Sellin, Karl; Babaev, Egor

2018-03-01

In multicomponent superfluids and superconductors, co- and counterflows of components have, in general, different properties. A. F. Andreev and E. P. Bashkin [Sov. Phys. JETP 42, 164 (1975)] discussed, in the context of He3/He4 superfluid mixtures, that interparticle interactions produce a dissipationless drag. The drag can be understood as a superflow of one component induced by phase gradients of the other component. Importantly, the drag can be both positive (entrainment) and negative (counterflow). The effect is known to have crucial importance for many properties of diverse physical systems ranging from the dynamics of neutron stars and rotational responses of Bose mixtures of ultracold atoms to magnetic responses of multicomponent superconductors. Although substantial literature exists that includes the drag interaction phenomenologically, only a few regimes are covered by quantitative studies of the microscopic origin of the drag and its dependence on microscopic parameters. Here we study the microscopic origin and strength of the drag interaction in a quantum system of two-component bosons on a lattice with short-range interaction. By performing quantum Monte Carlo simulations of a two-component Bose-Hubbard model we obtain dependencies of the drag strength on the boson-boson interactions and properties of the optical lattice. Of particular interest are the strongly correlated regimes where the ratio of coflow and counterflow superfluid stiffnesses can diverge, corresponding to the case of saturated drag.

A vacuum gauge based on an ultracold gas

NASA Astrophysics Data System (ADS)

Makhalov, V. B.; Turlapov, A. V.

2017-06-01

We report the design and application of a primary vacuum gauge based on an ultracold gas of atoms in an optical dipole trap. The pressure is calculated from the confinement time for atoms in the trap. The relationship between pressure and confinement time is established from the first principles owing to elimination of all channels introducing losses, except for knocking out an atom from the trap due to collisions with a residual gas particle. The method requires the knowledge of the gas chemical composition in the vacuum chamber, and, in the absence of this information, the systematic error is less than that of the ionisation sensor.

Simulation of the weakly interacting Bose gas relaxation for cases of various interaction types

NASA Astrophysics Data System (ADS)

Kartsev, P. F.; Kuznetsov, I. O.

2017-12-01

In this work, we investigate the role of interactions in the process of thermalization of a weakly interacting Bose gas. The system of kinetic equations based on the ‘Fermi’s golden rule’ is solved numerically using special transformation for calculation efficiency. We study the distribution function for particles in various conditions, including interaction with phonon subsystem, i.e. energy exchange with thermal bath. The possibility to achieve the state of Bose-Einstein condensation with specific values of parameters, is also discussed.

Observation of a Degenerate Fermi Gas Trapped by a Bose-Einstein Condensate

NASA Astrophysics Data System (ADS)

DeSalvo, B. J.; Patel, Krutik; Johansen, Jacob; Chin, Cheng

2017-12-01

We report on the formation of a stable quantum degenerate mixture of fermionic 6Li and bosonic 133Cs in an optical trap by sympathetic cooling near an interspecies Feshbach resonance. New regimes of quantum degenerate Bose-Fermi mixtures are identified. With moderate attractive interspecies interactions, we show that a degenerate Fermi gas of Li can be fully confined in a Cs Bose-Einstein condensate without external potentials. For stronger attraction where mean-field collapse is expected, no such instability is observed. Potential mechanisms to explain this phenomenon are discussed.

Noise thermometry with two weakly coupled Bose-Einstein condensates.

PubMed

Gati, Rudolf; Hemmerling, Börge; Fölling, Jonas; Albiez, Michael; Oberthaler, Markus K

2006-04-07

Here we report on the experimental investigation of thermally induced fluctuations of the relative phase between two Bose-Einstein condensates which are coupled via tunneling. The experimental control over the coupling strength and the temperature of the thermal background allows for the quantitative analysis of the phase fluctuations. Furthermore, we demonstrate the application of these measurements for thermometry in a regime where standard methods fail. With this we confirm that the heat capacity of an ideal Bose gas deviates from that of a classical gas as predicted by the third law of thermodynamics.

Canonical ensemble ground state and correlation entropy of Bose-Einstein condensate

NASA Astrophysics Data System (ADS)

Svidzinsky, Anatoly; Kim, Moochan; Agarwal, Girish; Scully, Marlan O.

2018-01-01

Constraint of a fixed total number of particles yields a correlation between the fluctuation of particles in different states in the canonical ensemble. Here we show that, below the temperature of Bose-Einstein condensation (BEC), the correlation part of the entropy of an ideal Bose gas is cancelled by the ground-state contribution. Thus, in the BEC region, the thermodynamic properties of the gas in the canonical ensemble can be described accurately in a simplified model which excludes the ground state and assumes no correlation between excited levels.

Perturbative thermodynamic geometry of nonextensive ideal classical, Bose, and Fermi gases.

PubMed

Mohammadzadeh, Hosein; Adli, Fereshteh; Nouri, Sahereh

2016-12-01

We investigate perturbative thermodynamic geometry of nonextensive ideal classical, Bose, and Fermi gases. We show that the intrinsic statistical interaction of nonextensive Bose (Fermi) gas is attractive (repulsive) similar to the extensive case but the value of thermodynamic curvature is changed by a nonextensive parameter. In contrary to the extensive ideal classical gas, the nonextensive one may be divided to two different regimes. According to the deviation parameter of the system to the nonextensive case, one can find a special value of fugacity, z^{*}, where the sign of thermodynamic curvature is changed. Therefore, we argue that the nonextensive parameter induces an attractive (repulsive) statistical interaction for zz^{*}) for an ideal classical gas. Also, according to the singular point of thermodynamic curvature, we consider the condensation of nonextensive Boson gas.

Mechanism of stimulated Hawking radiation in a laboratory Bose-Einstein condensate

NASA Astrophysics Data System (ADS)

Jacobson, Ted; Wang, Yi-Hsieh; Edwards, Mark; Clark, Charles W.

2017-01-01

Analog black/white hole pairs have been achieved in recent experiment by J. Steinhauer, using an elongated Bose-Einstein condensate. He reported observations of self-amplifying Hawking radiation, via a lasing mechanism operating between the black and white hole horizons. Through the simulations using the 1D Gross-Pitaevskii equation, we find that the experimental observations should be attributed not to the black hole laser effect, but rather to a growing zero-frequency bow wave, generated at the white-hole horizon. The relative motion of the black and white hole horizons produces a Doppler shift of the bow wave at the black hole, where it stimulates the emission of monochromatic Hawking radiation. This mechanism is confirmed using temporal and spatial windowed Fourier spectra of the condensate. We also find that shot-to-shot atom number variations, of the type normally realized in ultracold-atom experiments, and quantum fluctuations of condensates, as computed in the Bogoliubov-De Gennes approximation, give density-density correlations consistent with those reported in the experiments. In particular, atom number variations can produce a spurious correlation signal.

Finite-momentum Bose-Einstein condensates in shaken two-dimensional square optical lattices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Di Liberto, M.; Scuola Superiore di Catania, Universita di Catania, Via Valdisavoia 9, I-95123 Catania; Tieleman, O.

2011-07-15

We consider ultracold bosons in a two-dimensional square optical lattice described by the Bose-Hubbard model. In addition, an external time-dependent sinusoidal force is applied to the system, which shakes the lattice along one of the diagonals. The effect of the shaking is to renormalize the nearest-neighbor-hopping coefficients, which can be arbitrarily reduced, can vanish, or can even change sign, depending on the shaking parameter. Therefore, it is necessary to account for higher-order-hopping terms, which are renormalized differently by the shaking, and to introduce anisotropy into the problem. We show that the competition between these different hopping terms leads to finite-momentummore » condensates with a momentum that may be tuned via the strength of the shaking. We calculate the boundaries between the Mott insulator and the different superfluid phases and present the time-of-flight images expected to be observed experimentally. Our results open up possibilities for the realization of bosonic analogs of the Fulde, Ferrel, Larkin, and Ovchinnikov phase describing inhomogeneous superconductivity.« less

Bose-Einstein Condensates in 1D Optical Lattices: Nonlinearity and Wannier-Stark Spectra

NASA Astrophysics Data System (ADS)

Arimondo, Ennio; Ciampini, Donatella; Morsch, Oliver

The development of powerful laser cooling and trapping techniques has made possible the controlled realization of dense and cold gaseous samples, thus opening the way for investigations in the ultracold temperature regimes not accessible with conventional techniques. A Bose-Einstein condensate (BEC) represents a peculiar gaseous state where all the particles reside in the same quantum mechanical state. Therefore BECs exhibit quantum mechanical phe-nomena on a macroscopic scale with a single quantum mechanical wavefunction describing the external degrees of freedom. That control of the external degrees of freedom is combined with a precise control of the internal degrees. The BEC investigation has become a very active area of research in contem-porary physics. The BEC study encompasses different subfields of physics, i.e., atomic and molecular physics, quantum optics, laser spectroscopy, solid state physics. Atomic physics and laser spectroscopy provide the methods for creating and manipulating the atomic and molecular BECs. However owing to the interactions between the particles composing the condensate and to the configuration of the external potential, concepts and methods from solid state physics are extensively used for BEC description.

Thermal solitons as revealed by the static structure factor

NASA Astrophysics Data System (ADS)

Gawryluk, Krzysztof; Brewczyk, Mirosław; Rzążewski, Kazimierz

2017-04-01

We study, within a framework of the classical fields approximation, the static structure factor of a weakly interacting Bose gas at thermal equilibrium. As in a recent experiment [R. Schley et al., Phys. Rev. Lett. 111, 055301 (2013), 10.1103/PhysRevLett.111.055301], we find that the thermal distribution of phonons in a three-dimensional Bose gas follows the Planck distribution. On the other hand we find a disagreement between the Planck and phonon (calculated just as for the bulk gas) distributions in the case of elongated quasi-one-dimensional systems. We attribute this discrepancy to the existence of spontaneous dark solitons [i.e., thermal solitons as reported in T. Karpiuk et al., Phys. Rev. Lett. 109, 205302 (2012), 10.1103/PhysRevLett.109.205302] in an elongated Bose gas at thermal equilibrium.

On the ground state energy of the δ-function Bose gas

NASA Astrophysics Data System (ADS)

Tracy, Craig A.; Widom, Harold

2016-07-01

The weak coupling asymptotics, to order {(c/ρ )}2, of the ground state energy of the delta-function Bose gas is derived. Here 2c≥slant 0 is the delta-function potential amplitude and ρ the density of the gas in the thermodynamic limit. The analysis uses the electrostatic interpretation of the Lieb-Liniger integral equation. Dedicated to Professor Tony Guttmann on the occasion of his 70th birthday.

Three Body Recombination and Photoassociative Ultracold Collisions Studied Using Translational Energy

DTIC Science & Technology

2009-02-27

Sumission, or Preparation 1. "Multiple Scattering and the Density Distribution of a Cs MOT," R. Overstreet, P. Zabawa , J. Tallant, A. Schwettmann... Zabawa . J. Tallant, A. Schwettmann, J. Crawford, and J.P. Shaffer, DAMOP, Knoxville, TN, (2006). 6. "Ultracold Cs Rydberg Gas Dynamics," K.R

Quantum phase slips: from condensed matter to ultracold quantum gases.

PubMed

D'Errico, C; Abbate, S Scaffidi; Modugno, G

2017-12-13

Quantum phase slips (QPS) are the primary excitations in one-dimensional superfluids and superconductors at low temperatures. They have been well characterized in most condensed-matter systems, and signatures of their existence have been recently observed in superfluids based on quantum gases too. In this review, we briefly summarize the main results obtained on the investigation of phase slips from superconductors to quantum gases. In particular, we focus our attention on recent experimental results of the dissipation in one-dimensional Bose superfluids flowing along a shallow periodic potential, which show signatures of QPS.This article is part of the themed issue 'Breakdown of ergodicity in quantum systems: from solids to synthetic matter'. © 2017 The Author(s).

Quench dynamics in strongly correlated Bose-Hubbard chains

NASA Astrophysics Data System (ADS)

Naegerl, Hanns-Christoph

2013-05-01

We present a series of experiments in the context of 1D physics with ultracold atoms, combining optical lattice potentials with the capability to tune the strength of the onsite particle interaction U. For an array of tilted 1D chains with site-to-site tilt E and initial unity occupation we record the dynamics after a quench to the phase transition point U ~E by monitoring the number of doublons created as a function of time after the quench. We observe characteristic oscillations from which we deduce a shift of the resonance condition as time progresses. For U/2 ~E and U/3 ~E we observe coupling to next-nearest neighbors and beyond.

Quantized vortices in the ideal bose gas: a physical realization of random polynomials.

PubMed

Castin, Yvan; Hadzibabic, Zoran; Stock, Sabine; Dalibard, Jean; Stringari, Sandro

2006-02-03

We propose a physical system allowing one to experimentally observe the distribution of the complex zeros of a random polynomial. We consider a degenerate, rotating, quasi-ideal atomic Bose gas prepared in the lowest Landau level. Thermal fluctuations provide the randomness of the bosonic field and of the locations of the vortex cores. These vortices can be mapped to zeros of random polynomials, and observed in the density profile of the gas.

Calculation of the critical temperature of a dilute Bose gas in the Bogoliubov approximation

NASA Astrophysics Data System (ADS)

Napiórkowski, M.; Reuvers, R.; Solovej, J. P.

2018-01-01

Following an earlier calculation in 3D, we calculate the 2D critical temperature of a dilute, translation-invariant Bose gas using a variational formulation of the Bogoliubov approximation introduced by Critchley and Solomon in 1976. This provides the first analytical calculation of the Kosterlitz-Thouless transition temperature that includes the constant in the logarithm.

Extended Bose Hubbard model of interacting bosonic atoms in optical lattices: From superfluidity to density waves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mazzarella, G.; Giampaolo, S. M.; Illuminati, F.

2006-01-15

For systems of interacting, ultracold spin-zero neutral bosonic atoms, harmonically trapped and subject to an optical lattice potential, we derive an Extended Bose Hubbard (EBH) model by developing a systematic expansion for the Hamiltonian of the system in powers of the lattice parameters and of a scale parameter, the lattice attenuation factor. We identify the dominant terms that need to be retained in realistic experimental conditions, up to nearest-neighbor interactions and nearest-neighbor hoppings conditioned by the on-site occupation numbers. In the mean field approximation, we determine the free energy of the system and study the phase diagram both at zeromore » and at finite temperature. At variance with the standard on site Bose Hubbard model, the zero-temperature phase diagram of the EBH model possesses a dual structure in the Mott insulating regime. Namely, for specific ranges of the lattice parameters, a density wave phase characterizes the system at integer fillings, with domains of alternating mean occupation numbers that are the atomic counterparts of the domains of staggered magnetizations in an antiferromagnetic phase. We show as well that in the EBH model, a zero-temperature quantum phase transition to pair superfluidity is, in principle, possible, but completely suppressed at the lowest order in the lattice attenuation factor. Finally, we determine the possible occurrence of the different phases as a function of the experimentally controllable lattice parameters.« less

Stability of a Unitary Bose Gas

NASA Astrophysics Data System (ADS)

Fletcher, Richard J.; Gaunt, Alexander L.; Navon, Nir; Smith, Robert P.; Hadzibabic, Zoran

2013-09-01

We study the stability of a thermal K39 Bose gas across a broad Feshbach resonance, focusing on the unitary regime, where the scattering length a exceeds the thermal wavelength λ. We measure the general scaling laws relating the particle-loss and heating rates to the temperature, scattering length, and atom number. Both at unitarity and for positive a≪λ we find agreement with three-body theory. However, for a<0 and away from unitarity, we observe significant four-body decay. At unitarity, the three-body loss coefficient, L3∝λ4, is 3 times lower than the universal theoretical upper bound. This reduction is a consequence of species-specific Efimov physics and makes K39 particularly promising for studies of many-body physics in a unitary Bose gas.

Conserving and gapless Hartree-Fock-Bogoliubov theory for the three-dimensional dilute Bose gas

NASA Astrophysics Data System (ADS)

Zhang, Ya-Hui; Li, Dingping

2013-11-01

The excitation spectrum for the three-dimensional Bose gas in the Bose-Einstein condensation phase is calculated nonperturbatively with the modified Hartree-Fock-Bogoliubov theory, which is both conserving and gapless. From improved Φ-derivable theory, the diagrams needed to preserve the Ward-Takahashi identity are re-summed in a systematic and nonperturbative way. It is valid up to the critical temperature where the dispersion relation of the low-energy excitation spectrum changes from linear to quadratic. Because including the higher-order fluctuation, the results show significant improvement on the calculation of the shift of critical temperature with other conserving and gapless theories.

Ultracold molecules for the masses: Evaporative cooling and magneto-optical trapping

NASA Astrophysics Data System (ADS)

Stuhl, B. K.

While cold molecule experiments are rapidly moving towards their promised benefits of precision spectroscopy, controllable chemistry, and novel condensed phases, heretofore the field has been greatly limited by a lack of methods to cool and compress chemically diverse species to temperatures below ten millikelvin. While in atomic physics these needs are fulfilled by laser cooling, magneto-optical trapping, and evaporative cooling, until now none of these techniques have been applicable to molecules. In this thesis, two major breakthroughs are reported. The first is the observation of evaporative cooling in magnetically trapped hydroxyl (OH) radicals, which potentially opens a path all the way to Bose-Einstein condensation of dipolar radicals, as well as allowing cold- and ultracold-chemistry studies of fundamental reaction mechanisms. Through the combination of an extremely high gradient magnetic quadrupole trap and the use of the OH Λ-doublet transition to enable highly selective forced evaporation, cooling by an order of magnitude in temperature was achieved and yielded a final temperature no higher than 5mK. The second breakthrough is the successful application of laser cooling and magneto-optical trapping to molecules. Motivated by a proposal in this thesis, laser cooling of molecules is now known to be technically feasible in a select but substantial pool of diatomic molecules. The demonstration of not only Doppler cooling but also two-dimensional magneto-optical trapping in yttrium (II) oxide, YO, is expected to enable rapid growth in the availability of ultracold molecules—just as the invention of the atomic magneto-optical trap stimulated atomic physics twenty-five years ago.

Detecting Friedel oscillations in ultracold Fermi gases

NASA Astrophysics Data System (ADS)

Riechers, Keno; Hueck, Klaus; Luick, Niclas; Lompe, Thomas; Moritz, Henning

2017-09-01

Investigating Friedel oscillations in ultracold gases would complement the studies performed on solid state samples with scanning-tunneling microscopes. In atomic quantum gases interactions and external potentials can be tuned freely and the inherently slower dynamics allow to access non-equilibrium dynamics following a potential or interaction quench. Here, we examine how Friedel oscillations can be observed in current ultracold gas experiments under realistic conditions. To this aim we numerically calculate the amplitude of the Friedel oscillations which are induced by a potential barrier in a 1D Fermi gas and compare it to the expected atomic and photonic shot noise in a density measurement. We find that to detect Friedel oscillations the signal from several thousand one-dimensional systems has to be averaged. However, as up to 100 parallel one-dimensional systems can be prepared in a single run with present experiments, averaging over about 100 images is sufficient.

Application of exergetic sustainability index to a nano-scale irreversible Brayton cycle operating with ideal Bose and Fermi gasses

NASA Astrophysics Data System (ADS)

Açıkkalp, Emin; Caner, Necmettin

2015-09-01

In this study, a nano-scale irreversible Brayton cycle operating with quantum gasses including Bose and Fermi gasses is researched. Developments in the nano-technology cause searching the nano-scale machines including thermal systems to be unavoidable. Thermodynamic analysis of a nano-scale irreversible Brayton cycle operating with Bose and Fermi gasses was performed (especially using exergetic sustainability index). In addition, thermodynamic analysis involving classical evaluation parameters such as work output, exergy output, entropy generation, energy and exergy efficiencies were conducted. Results are submitted numerically and finally some useful recommendations were conducted. Some important results are: entropy generation and exergetic sustainability index are affected mostly for Bose gas and power output and exergy output are affected mostly for the Fermi gas by x. At the high temperature conditions, work output and entropy generation have high values comparing with other degeneracy conditions.

Entropy of the Bose-Einstein-condensate ground state: Correlation versus ground-state entropy

NASA Astrophysics Data System (ADS)

Kim, Moochan B.; Svidzinsky, Anatoly; Agarwal, Girish S.; Scully, Marlan O.

2018-01-01

Calculation of the entropy of an ideal Bose-Einstein condensate (BEC) in a three-dimensional trap reveals unusual, previously unrecognized, features of the canonical ensemble. It is found that, for any temperature, the entropy of the Bose gas is equal to the entropy of the excited particles although the entropy of the particles in the ground state is nonzero. We explain this by considering the correlations between the ground-state particles and particles in the excited states. These correlations lead to a correlation entropy which is exactly equal to the contribution from the ground state. The correlations themselves arise from the fact that we have a fixed number of particles obeying quantum statistics. We present results for correlation functions between the ground and excited states in a Bose gas, so as to clarify the role of fluctuations in the system. We also report the sub-Poissonian nature of the ground-state fluctuations.

Onset of nanoscale dissipation in superfluid 4He at zero temperature: Role of vortex shedding and cavitation

NASA Astrophysics Data System (ADS)

Ancilotto, Francesco; Barranco, Manuel; Eloranta, Jussi; Pi, Martí

2017-08-01

Two-dimensional flow past an infinitely long cylinder of nanoscopic radius in superfluid 4He at zero temperature is studied using time-dependent density-functional theory. The calculations reveal two distinct critical phenomena for the onset of dissipation: (i) vortex-antivortex pair shedding from the periphery of the moving cylinder, and (ii) the appearance of cavitation in the wake, which possesses similar geometry to that observed experimentally for fast-moving micrometer-scale particles in superfluid 4He. The formation of cavitation bubbles behind the cylinder is accompanied by a sudden jump in the drag exerted on the moving cylinder by the fluid. Vortex pairs with the same circulation are occasionally emitted in the form of dimers, which constitute the building blocks for the Benard-von Karman vortex street structure observed in classical turbulent fluids and Bose-Einstein condensates. The cavitation-induced dissipation mechanism should be common to all superfluids that are self-bound and have a finite surface tension, which include the recently discovered self-bound droplets in ultracold Bose gases. These systems would provide an ideal testing ground for further exploration of this mechanism experimentally.

Effect of the band structure in a rigorous two-body model with long-range interactions in 1D optical lattices

NASA Astrophysics Data System (ADS)

Kristensen, Tom; Simoni, Andrea; Launay, Jean-Michel

2016-05-01

We compute scattering and bound state properties for two ultracold molecules in a pure 1D optical lattice. We introduce reference functions with complex quasi-momentum that naturally account for the effect of excited energy bands. Our exact results for a short-range interaction are first compared with the simplest version of the standard Bose-Hubbard (BH) model. Such comparison allows us to highlight the effect of the excited bands, of the non-on-site interaction and of tunneling with distant neighbor, that are not taken into account in the BH model. The effective interaction can depend strongly on the particle quasi-momenta and can present a resonant behavior even in a deep lattice. As a second step, we study scattering of two polar particles in the optical lattice. Peculiar Wigner threshold laws stem from the interplay of the long range dipolar interaction and the presence of the energy bands. We finally assess the validity of an extended Bose-Hubbard model for dipolar gases based on our exact two-body calculations. This work was supported by the Agence Nationale de la Recherche (Contract No. ANR-12-BS04-0020-01).

Engineering frequency-dependent superfluidity in Bose-Fermi mixtures

NASA Astrophysics Data System (ADS)

Arzamasovs, Maksims; Liu, Bo

2018-04-01

Unconventional superconductivity and superfluidity are among the most exciting and fascinating quantum phenomena in condensed-matter physics. Usually such states are characterized by nontrivial spin or spatial symmetry of the pairing order parameter, such as "spin triplet" or "p wave." However, besides spin and spatial dependence the order parameter may have unconventional frequency dependence which is also permitted by Fermi-Dirac statistics. Odd-frequency fermionic pairing is an exciting paradigm when discussing exotic superfluidity or superconductivity and is yet to be realized in experiments. In this paper we propose a symmetry-based method of controlling frequency dependence of the pairing order parameter via manipulating the inversion symmetry of the system. First, a toy model is introduced to illustrate that frequency dependence of the order parameter can be achieved through our proposed approach. Second, by taking advantage of recent rapid developments in producing spin-orbit-coupled dispersions in ultracold gases, we propose a Bose-Fermi mixture to realize such frequency-dependent superfluid. The key idea is introducing the frequency-dependent attraction between fermions mediated by Bogoliubov phonons with asymmetric dispersion. Our proposal should pave an alternative way for exploring frequency-dependent superfluids with cold atoms.

Thermodynamics and Dynamics of Bose condensation in a quasi-homogeneous gas

NASA Astrophysics Data System (ADS)

Navon, Nir; Schmidutz, Tobias; Gotlibovych, Igor; Gaunt, Alexander; Robert-de-Saint-Vincent, Martin; Smith, Robert; Hadzibabic, Zoran

2014-05-01

We present an experimental study of the thermodynamics and dynamics of Bose-Einstein condensation (BEC) in an optical-box trap. We first characterize the critical point for BEC, and observe saturation of the thermal component in a partially condensed cloud, in agreement with Einstein's textbook picture of a purely statistical phase transition. We also observed the quantum Joule-Thomson effect, namely isoenthalpic cooling of a non-interacting gas. We then investigate the dynamics of Bose condensation in the box potential following a rapid temperature quench through the phase transition, and focus on the time-evolution of the condensed fraction, the coherence length and the mean-field shift, that we probe via Bragg spectroscopy.

Non-equilibrium Properties of a Pumped-Decaying Bose-Condensed Electron–Hole Gas in the BCS–BEC Crossover Region

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hanai, R.; Littlewood, P. B.; Ohashi, Y.

2016-03-01

We theoretically investigate a Bose-condensed exciton gas out of equilibrium. Within the framework of the combined BCS-Leggett strong-coupling theory with the non-equilibrium Keldysh formalism, we show how the Bose-Einstein condensation (BEC) of excitons is suppressed to eventually disappear, when the system is in the non-equilibrium steady state. The supply of electrons and holes from the bath is shown to induce quasi-particle excitations, leading to the partial occupation of the upper branch of Bogoliubov single-particle excitation spectrum. We also discuss how this quasi-particle induction is related to the suppression of exciton BEC, as well as the stability of the steady state.

Perron-Frobenius theorem on the superfluid transition of an ultracold Fermi gas

NASA Astrophysics Data System (ADS)

Sakumichi, Naoyuki; Kawakami, Norio; Ueda, Masahito

2014-05-01

The Perron-Frobenius theorem is applied to identify the superfluid transition of the BCS-BEC crossover based on a cluster expansion method of Lee and Yang. Here, the cluster expansion is a systematic expansion of the equation of state (EOS) in terms of the fugacity z = exp (βμ) as βpλ3 = 2 z +b2z2 +b3z3 + ⋯ , with inverse temperature β =(kB T) - 1 , chemical potential μ, pressure p, and thermal de Broglie length λ =(2 πℏβ / m) 1 / 2 . According to the method of Lee and Yang, EOS is expressed by the Lee-Yang graphs. A singularity of an infinite series of ladder-type Lee-Yang graphs is analyzed. We point out that the singularity is governed by the Perron-Frobenius eigenvalue of a certain primitive matrix which is defined in terms of the two-body cluster functions and the Fermi distribution functions. As a consequence, it is found that there exists a unique fugacity at the phase transition point, which implies that there is no fragmentation of Bose-Einstein condensates of dimers and Cooper pairs at the ladder-approximation level of Lee-Yang graphs. An application to a BEC of strongly bounded dimers is also made.

Evaporative cooling of the dipolar hydroxyl radical.

PubMed

Stuhl, Benjamin K; Hummon, Matthew T; Yeo, Mark; Quéméner, Goulven; Bohn, John L; Ye, Jun

2012-12-20

Atomic physics was revolutionized by the development of forced evaporative cooling, which led directly to the observation of Bose-Einstein condensation, quantum-degenerate Fermi gases and ultracold optical lattice simulations of condensed-matter phenomena. More recently, substantial progress has been made in the production of cold molecular gases. Their permanent electric dipole moment is expected to generate systems with varied and controllable phases, dynamics and chemistry. However, although advances have been made in both direct cooling and cold-association techniques, evaporative cooling has not been achieved so far. This is due to unfavourable ratios of elastic to inelastic scattering and impractically slow thermalization rates in the available trapped species. Here we report the observation of microwave-forced evaporative cooling of neutral hydroxyl (OH(•)) molecules loaded from a Stark-decelerated beam into an extremely high-gradient magnetic quadrupole trap. We demonstrate cooling by at least one order of magnitude in temperature, and a corresponding increase in phase-space density by three orders of magnitude, limited only by the low-temperature sensitivity of our spectroscopic thermometry technique. With evaporative cooling and a sufficiently large initial population, much colder temperatures are possible; even a quantum-degenerate gas of this dipolar radical (or anything else it can sympathetically cool) may be within reach.

Dicke superradiance as nondestructive probe for the state of atoms in optical lattices

NASA Astrophysics Data System (ADS)

ten Brinke, Nicolai; Schützhold, Ralf

2016-04-01

We present a proposal for a probing scheme utilizing Dicke superradiance to obtain information about ultracold atoms in optical lattices. A probe photon is absorbed collectively by an ensemble of lattice atoms generating a Dicke state. The lattice dynamics (e.g., tunneling) affects the coherence properties of that Dicke state and thus alters the superradiant emission characteristics - which in turn provides insight into the lattice (dynamics). Comparing the Bose-Hubbard and the Fermi-Hubbard model, we find similar superradiance in the strongly interacting Mott insulator regime, but crucial differences in the weakly interacting (superfluid or metallic) phase. Furthermore, we study the possibility to detect whether a quantum phase transition between the two regimes can be considered adiabatic or a quantum quench.

Spatially distributed multipartite entanglement enables EPR steering of atomic clouds

NASA Astrophysics Data System (ADS)

Kunkel, Philipp; Prüfer, Maximilian; Strobel, Helmut; Linnemann, Daniel; Frölian, Anika; Gasenzer, Thomas; Gärttner, Martin; Oberthaler, Markus K.

2018-04-01

A key resource for distributed quantum-enhanced protocols is entanglement between spatially separated modes. However, the robust generation and detection of entanglement between spatially separated regions of an ultracold atomic system remain a challenge. We used spin mixing in a tightly confined Bose-Einstein condensate to generate an entangled state of indistinguishable particles in a single spatial mode. We show experimentally that this entanglement can be spatially distributed by self-similar expansion of the atomic cloud. We used spatially resolved spin read-out to reveal a particularly strong form of quantum correlations known as Einstein-Podolsky-Rosen (EPR) steering between distinct parts of the expanded cloud. Based on the strength of EPR steering, we constructed a witness, which confirmed genuine 5-partite entanglement.

Intertwined and vestigial order with ultracold atoms in multiple cavity modes

NASA Astrophysics Data System (ADS)

Gopalakrishnan, Sarang; Shchadilova, Yulia E.; Demler, Eugene

2017-12-01

Atoms in transversely pumped optical cavities "self-organize" by forming a density wave and emitting superradiantly into the cavity mode(s). For a single-mode cavity, the properties of this self-organization transition are well characterized both theoretically and experimentally. Here, we explore the self-organization of a Bose-Einstein condensate in the presence of two cavity modes—a system that recently was realized experimentally [Léonard et al., Nature (London) 543, 87 (2017), 10.1038/nature21067]. We argue that this system can exhibit a "vestigially ordered" phase in which neither cavity mode exhibits superradiance but the cavity modes are mutually phase locked by the atoms. We argue that this vestigially ordered phase should generically be present in multimode cavity geometries.

Gibbons-Hawking effect in the sonic de Sitter space-time of an expanding Bose-Einstein-condensed gas.

PubMed

Fedichev, Petr O; Fischer, Uwe R

2003-12-12

We propose an experimental scheme to observe the Gibbons-Hawking effect in the acoustic analog of a (1+1)-dimensional de Sitter universe, produced in an expanding, cigar-shaped Bose-Einstein condensate. It is shown that a two-level system created at the center of the trap, an atomic quantum dot interacting with phonons, observes a thermal Bose distribution at the de Sitter temperature.

Effects of Interaction Imbalance in a Strongly Repulsive One-Dimensional Bose Gas

NASA Astrophysics Data System (ADS)

Barfknecht, R. E.; Foerster, A.; Zinner, N. T.

2018-05-01

We calculate the spatial distributions and the dynamics of a few-body two-component strongly interacting Bose gas confined to an effectively one-dimensional trapping potential. We describe the densities for each component in the trap for different interaction and population imbalances. We calculate the time evolution of the system and show that, for a certain ratio of interactions, the minority population travels through the system as an effective wave packet.

Chemical potential of quasi-equilibrium magnon gas driven by pure spin current.

PubMed

Demidov, V E; Urazhdin, S; Divinskiy, B; Bessonov, V D; Rinkevich, A B; Ustinov, V V; Demokritov, S O

2017-11-17

Pure spin currents provide the possibility to control the magnetization state of conducting and insulating magnetic materials. They allow one to increase or reduce the density of magnons, and achieve coherent dynamic states of magnetization reminiscent of the Bose-Einstein condensation. However, until now there was no direct evidence that the state of the magnon gas subjected to spin current can be treated thermodynamically. Here, we show experimentally that the spin current generated by the spin-Hall effect drives the magnon gas into a quasi-equilibrium state that can be described by the Bose-Einstein statistics. The magnon population function is characterized either by an increased effective chemical potential or by a reduced effective temperature, depending on the spin current polarization. In the former case, the chemical potential can closely approach, at large driving currents, the lowest-energy magnon state, indicating the possibility of spin current-driven Bose-Einstein condensation.

Progress towards a rapidly rotating ultracold Fermi gas

NASA Astrophysics Data System (ADS)

Hu, Ming-Guang; van de Graaff, Michael; Cornell, Eric; Jin, Deborah

2015-05-01

We are designing an experiment with the goal of creating a rapidly rotating ultracold Fermi gas, which is promising system in which to study quantum Hall physics. We propose to use selective evaporation of a gas that has been initialized with a modest rotation rate to increase the angular momentum per particle in order to reach rapid rotation. We have performed simulations of this evaporation process for a model optical trap potential. Achieving rapid rotation will require a very smooth, very harmonic, and dynamically variable optical trap. We plan to use a setup consisting of two acousto-optical modulators to ``paint'' an optical dipole trapping potential that can be made smooth, radially symmetric, and harmonic. This project is supported by NSF, NIST, NASA.

De Haas-van Alphen effect of a two-dimensional ultracold atomic gas

NASA Astrophysics Data System (ADS)

Farias, B.; Furtado, C.

2016-01-01

In this paper, we show how the ultracold atom analogue of the two-dimensional de Haas-van Alphen effect in electronic condensed matter systems can be induced by optical fields in a neutral atomic system. The interaction between the suitable spatially varying laser fields and tripod-type trapped atoms generates a synthetic magnetic field which leads the particles to organize themselves in Landau levels. Initially, with the atomic gas in a regime of lowest Landau level, we display the oscillatory behaviour of the atomic energy and its derivative with respect to the effective magnetic field (B) as a function of 1/B. Furthermore, we estimate the area of the Fermi circle of the two-dimensional atomic gas.

EDITORIAL: Focus on Quantum Correlations in Tailored Matter

NASA Astrophysics Data System (ADS)

Muramatsu, Alejandro; Pfau, Tilman

2008-04-01

At low enough temperatures and at microscopic length scales the laws of quantum mechanics become apparent. The underlying superposition principle leads to interference phenomena for one degree of freedom and to the concept of entanglement for two and more. Entangled degrees of freedom are often correlated beyond their classically allowed correlation. These quantum correlations also appear in very large systems and are caused by strong interactions between the constituents. Strongly correlated forms of quantum matter became ubiquitous in condensed matter physics, with the discovery of heavy fermion materials, cuprates and other unconventional superconductors. Here the main players are electrons embedded in solid matter. But they also can be found in interacting quantum gases, where the main players are atoms. In the latter case the required temperatures for quantum correlations to appear are much lower. But in turn the length scales are larger and they can be embedded in well controlled potentials. A fascinating possibility offered by present day technologies is to tailor matter in order to induce the emergence of new phenomena by controlling quantum correlations. One of the routes leading to spectacular advances is the configuration of nanomaterials like quantum dots or quantum wires on the basis of semiconducting substrates that allow, e.g., to manipulate the Kondo effect or Luttinger liquids affecting transport properties through such nanostructures. Another quite different route with at the moment unlimited potential is offered by quantum optics and atomic physics, when implemented to bring quantum gases into the strongly interacting regime. This can be achieved by optical lattices leading to Mott-insulators, or to two dimensional systems displaying Kosterlitz-Thouless behavior in bosonic gases, or by Feshbach resonances, leading to fermionic systems with unconventional superfluid states like the Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) one. In spite of the very different experimental realizations leading to the two routes mentioned above, they share a common goal, namely achieving a deep understanding of quantum correlations that will ultimately allow to control them and possibly realize new forms of matter. They also share the flexibility that allows to increase the complexity in quantum correlations by joining in a controlled manner well understood building units and/or by regulating their coupling to the environment. It is under the common goal of understanding and controlling quantum correlations that we see the topics presented in this focus issue of New Journal of Physics, where both lines of development, that is on solid-state substrates or with quantum gases, give a timely view of the advances towards the above mentioned common goal. Focus on Quantum Correlations in Tailored Matter Contents Temperature changes when adiabatically ramping up an optical lattice Lode Pollet, Corinna Kollath, Kris Van Houcke and Matthias Troyer Numerical study of two-body correlation in a 1D lattice with perfect blockade B Sun and F Robicheaux Kinetic Monte Carlo modeling of dipole blockade in Rydberg excitation experiment Amodsen Chotia, Matthieu Viteau, Thibault Vogt, Daniel Comparat and Pierre Pillet Motion of Rydberg atoms induced by resonant dipole-dipole interactions C Ates, A Eisfeld and J M Rost Quantum coherence due to Bose-Einstein condensation of parametrically driven magnons S O Demokritov, V E Demidov, O Dzyapko, G A Melkov and A N Slavin Chaotic dynamics in spinor Bose-Einstein condensates J Kronjäger, K Sengstock and K Bongs Damped Bloch oscillations of Bose-Einstein condensates in disordered potential gradients S Drenkelforth, G Kleine Büning, J Will, T Schulte, N Murray, W Ertmer, L Santos and J J Arlt Rabi oscillations between ground and Rydberg states and van der Waals blockade in a mesoscopic frozen Rydberg gas M Reetz-Lamour, J Deiglmayr, T Amthor and M Weidemüller Excitations in two-component Bose gases A Kleine, C Kollath, I P McCulloch, T Giamarchi and U Schollwöck Exploring the growth of correlations in a quasi one-dimensional trapped Bose gas M Eckart, R Walser and W P Schleich How to fix a broken symmetry: quantum dynamics of symmetry restoration in a ferromagnetic Bose-Einstein condensate Bogdan Damski and Wojciech H Zurek Landau levels of cold atoms in non-Abelian gauge fields A Jacob, P Öhberg, G Juzeliunas and L Santos Atomic four-wave mixing via condensate collisions A Perrin, C M Savage, D Boiron, V Krachmalnicoff, C I Westbrook and K V Kheruntsyan Semifluxons in superconductivity and cold atomic gases R Walser, E Goldobin, O Crasser, D Koelle, R Kleiner and W P Schleich Disorder-induced trapping versus Anderson localization in Bose-Einstein condensates expanding in disordered potentials L Sanchez-Palencia, D Clément, P Lugan, P Bouyer and A Aspect Critical tunneling currents in the regime of bilayer excitons L Tiemann, W Dietsche, M Hauser and K von Klitzing Quantum phases of trapped ions in an optical lattice R Schmied, T Roscilde, V Murg, D Porras and J I Cirac Generation and detection of a spin entanglement in nonequilibrium quantum dots Stefan Legel, Jürgen König and Gerd Schön Slow light in inhomogeneous and transverse fields Leon Karpa and Martin Weitz FFLO state in 1-, 2- and 3-dimensional optical lattices combined with a non-uniform background potential T K Koponen, T Paananen, J-P Martikainen, M R Bakhtiari and P Törmä Geometry-dependent interplay of long- and short-range interactions in ultracold fermionic gases: models for condensed matter and astrophysics B Deb, G Kurizki and I E Mazets Fermionic renormalization group methods for transport through inhomogeneous Luttinger liquids V Meden, S Andergassen, T Enss, H Schoeller and K Schönhammer Luttinger hydrodynamics of confined one-dimensional Bose gases with dipolar interactions R Citro, S De Palo, E Orignac, P Pedri and M-L Chiofalo Towards deterministically controlled InGaAs/GaAs lateral quantum dot molecules L Wang, A Rastelli, S Kiravittaya, P Atkinson, F Ding, C C Bof Bufon, C Hermannstädter, M Witzany, G J Beirne, P Michler and O G Schmidt Effective parameters for weakly coupled Bose-Einstein condensates S Giovanazzi, J Esteve and M K Oberthaler Current statistics of correlated charge tunnelling through an impurity in a 1D wire Alexander Herzog and Ulrich Weiss Sideband cooling and coherent dynamics in a microchip multi-segmented ion trap Stephan A Schulz, Ulrich Poschinger, Frank Ziesel and Ferdinand Schmidt-Kaler The trapped two-dimensional Bose gas: from Bose-Einstein condensation to Berezinskii-Kosterlitz-Thouless physics Z Hadzibabic, P Krüger, M Cheneau, S P Rath and J Dalibard Dynamical protection of quantum computation from decoherence in laser-driven cold-ion and cold-atom systems Goren Gordon and Gershon Kurizki Spin-flip and spin-conserving optical transitions of the nitrogen-vacancy centre in diamond Ph Tamarat, N B Manson, J P Harrison, R L McMurtrie, A Nizovtsev, C Santori, R G Beausoleil, P Neumann, T Gaebel, F Jelezko, P Hemmer and J Wrachtrup Superconductivity in the attractive Hubbard model: functional renormalization group analysis R Gersch, C Honerkamp and W Metzner Quantum stability of Mott-insulator states of ultracold atoms in optical resonators Jonas Larson, Sonia Fernández-Vidal, Giovanna Morigi and Maciej Lewenstein

Polychronakos statistics and α-deformed Bose condensation of α-bosons

NASA Astrophysics Data System (ADS)

Chung, Won Sang; Hassanabadi, Hassan

2018-02-01

In this paper, we consider the Polychronakos statistics for α < 0. We use the Stirling formula for the α-Gamma function to find the distribution function for the α-bosons. As application, we discuss the α-deformed Bose condensation for α-boson gas.

Heating of trapped ultracold atoms by collapse dynamics

NASA Astrophysics Data System (ADS)

Laloë, Franck; Mullin, William J.; Pearle, Philip

2014-11-01

The continuous spontaneous localization (CSL) theory alters the Schrödinger equation. It describes wave-function collapse as a dynamical process instead of an ill-defined postulate, thereby providing macroscopic uniqueness and solving the so-called measurement problem of standard quantum theory. CSL contains a parameter λ giving the collapse rate of an isolated nucleon in a superposition of two spatially separated states and, more generally, characterizing the collapse time for any physical situation. CSL is experimentally testable, since it predicts some behavior different from that predicted by standard quantum theory. One example is the narrowing of wave functions, which results in energy imparted to particles. Here we consider energy given to trapped ultracold atoms. Since these are the coldest samples under experimental investigation, it is worth inquiring how they are affected by the CSL heating mechanism. We examine the CSL heating of a Bose-Einstein condensate (BEC) in contact with its thermal cloud. Of course, other mechanisms also provide heat and also particle loss. From varied data on optically trapped cesium BECs, we present an energy audit for known heating and loss mechanisms. The result provides an upper limit on CSL heating and thereby an upper limit on the parameter λ . We obtain λ ≲1 (±1 ) ×10-7 s-1.

Observation of Spin Polarons in a Tunable Fermi Liquid of Ultracold Atoms

NASA Astrophysics Data System (ADS)

Zwierlein, Martin

2009-05-01

We have observed spin polarons, dressed spin down impurities in a spin up Fermi sea of ultracold atoms via tomographic RF spectroscopy. Feshbach resonances allow to freely tune the interactions between the two spin states involved. A single spin down atom immersed in a Fermi sea of spin up atoms can do one of two things: For strong attraction, it can form a molecule with exactly one spin up partner, but for weaker interaction it will spread its attraction and surround itself with a collection of majority atoms. This spin down atom dressed with a spin up cloud constitutes the spin- or Fermi polaron. We have observed a striking spectroscopic signature of this quasi-particle for various interaction strengths, a narrow peak in the spin down spectrum that emerges above a broad background. The spectra allow us to directly measure the polaron energy and the quasi-particle residue Z. The polarons are found to be only weakly interacting with each other, and can thus be identified with the quasi-particles of Landau's Fermi liquid theory. At a critical interaction strength, we observe a transition from spin one-half polarons to spin zero molecules. At this point the Fermi liquid undergoes a phase transition into a superfluid Bose liquid.

Quantum Simulation of the Hubbard Model Using Ultra-Cold Atoms

DTIC Science & Technology

2008-11-01

explore phases that do not yet have analogous behavior in QCD . ..,.. Ultracold fennions in optical lattices . The evolution from BCS to BEC...trimer states. The three-component Fermi gas we have created will, when confined in an optical lattice , be an experimental realization of the SU(3...chromodynamics ( QCD ): the color superconducting phase and the formation of baryons. Our initial investigations have focused on understanding three-body

Ultracold Nonreactive Molecules in an Optical Lattice: Connecting Chemistry to Many-Body Physics.

PubMed

Doçaj, Andris; Wall, Michael L; Mukherjee, Rick; Hazzard, Kaden R A

2016-04-01

We derive effective lattice models for ultracold bosonic or fermionic nonreactive molecules (NRMs) in an optical lattice, analogous to the Hubbard model that describes ultracold atoms in a lattice. In stark contrast to the Hubbard model, which is commonly assumed to accurately describe NRMs, we find that the single on-site interaction parameter U is replaced by a multichannel interaction, whose properties we elucidate. Because this arises from complex short-range collisional physics, it requires no dipolar interactions and thus occurs even in the absence of an electric field or for homonuclear molecules. We find a crossover between coherent few-channel models and fully incoherent single-channel models as the lattice depth is increased. We show that the effective model parameters can be determined in lattice modulation experiments, which, consequently, measure molecular collision dynamics with a vastly sharper energy resolution than experiments in a free-space ultracold gas.

Making a molecular gas in the quantum regime

NASA Astrophysics Data System (ADS)

Ni, Kang-Kuen

2017-04-01

Ultracold molecules are exciting systems for a large range of scientific explorations including studies of novel phases of matter and precision measurement. In this talk, I will present a brief story of the first quantum gas of molecules, KRb, created under my PhD advisor, Deborah Jin, in 2008. A complete surprise was finding ultracold chemistry in such a system through measurements of reactant losses. In particular, long-range physics that determines KRb reactant collision rates, including van der Waals interactions, quantum statistics, and dipolar interactions, were studied extensively. However, the short-range behavior of these chemical reactions remains unknown. A legacy of her work is carried out in my lab at Harvard, where we are integrating physical chemistry tools with cold atom techniques to study ultracold chemistry with KRb molecules. In particular, we aim to elucidate the four-center reaction 2 KRb ->K2 + Rb2 by detecting the reaction products through ionization - both identify the product species and mapping out their complete quantum states.

Stable spin domains in a nondegenerate ultracold gas

NASA Astrophysics Data System (ADS)

Graham, S. D.; Niroomand, D.; Ragan, R. J.; McGuirk, J. M.

2018-05-01

We study the stability of two-domain spin structures in an ultracold gas of magnetically trapped 87Rb atoms above quantum degeneracy. Adding a small effective magnetic field gradient stabilizes the domains via coherent collective spin rotation effects, despite negligibly perturbing the potential energy relative to the thermal energy. We demonstrate that domain stabilization is accomplished through decoupling the dynamics of longitudinal magnetization, which remains in time-independent domains, from transverse magnetization, which undergoes a purely transverse spin wave trapped within the domain wall. We explore the effect of temperature and density on the steady-state domains, and compare our results to a hydrodynamic solution to a quantum Boltzmann equation.

Instability of Bose-Einstein condensation into the one-particle ground state on quantum graphs under repulsive perturbations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bolte, Jens, E-mail: jens.bolte@rhul.ac.uk; Kerner, Joachim, E-mail: joachim.kerner@fernuni-hagen.de

In this paper we investigate Bose-Einstein condensation into the one-particle ground state in interacting quantum many-particle systems on graphs. We extend previous results obtained for particles on an interval and show that even arbitrarily small repulsive two-particle interactions destroy the condensate in the one-particle ground state present in the non-interacting Bose gas. Our results also cover singular two-particle interactions, such as the well-known Lieb-Liniger model, in the thermodynamic limit.

Two characteristic temperatures for a Bose-Einstein condensate of a finite number of particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Idziaszek, Z.; Institut fuer Theoretische Physik, Universitaet Hannover, D-30167 Hannover,; Rzazewski, K.

2003-09-01

We consider two characteristic temperatures for a Bose-Einstein condensate, which are related to certain properties of the condensate statistics. We calculate them for an ideal gas confined in power-law traps and show that they approach the critical temperature in the limit of large number of particles. The considered characteristic temperatures can be useful in the studies of Bose-Einstein condensates of a finite number of atoms indicating the point of a phase transition.

Impurity self-energy in the strongly-correlated Bose systems

NASA Astrophysics Data System (ADS)

Panochko, Galyna; Pastukhov, Volodymyr; Vakarchuk, Ivan

2018-02-01

We proposed the nonperturbative scheme for the calculation of the impurity spectrum in the Bose system at zero temperature. The method is based on the path-integral formulation and describes an impurity as a zero-density ideal Fermi gas interacting with Bose system for which the action is written in terms of density fluctuations. On the example of the 3He atom immersed in the liquid helium-4 a good consistency with experimental data and results of Monte Carlo simulations is shown.

Relaxation of a High-Energy Quasiparticle in a One-Dimensional Bose Gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tan, Shina; Glazman, Leonid I.; Pustilnik, Michael

2010-08-27

We evaluate the relaxation rate of high-energy quasiparticles in a weakly interacting one-dimensional Bose gas. Unlike in higher dimensions, the rate is a nonmonotonic function of temperature, with a maximum at the crossover to the state of suppressed density fluctuations. At the maximum, the relaxation rate may significantly exceed its zero-temperature value. We also find the dependence of the differential inelastic scattering rate on the transferred energy. This rate yields information about temperature dependence of local pair correlations.

Superfluid transition of homogeneous and trapped two-dimensional Bose gases.

PubMed

Holzmann, Markus; Baym, Gordon; Blaizot, Jean-Paul; Laloë, Franck

2007-01-30

Current experiments on atomic gases in highly anisotropic traps present the opportunity to study in detail the low temperature phases of two-dimensional inhomogeneous systems. Although, in an ideal gas, the trapping potential favors Bose-Einstein condensation at finite temperature, interactions tend to destabilize the condensate, leading to a superfluid Kosterlitz-Thouless-Berezinskii phase with a finite superfluid mass density but no long-range order, as in homogeneous fluids. The transition in homogeneous systems is conveniently described in terms of dissociation of topological defects (vortex-antivortex pairs). However, trapped two-dimensional gases are more directly approached by generalizing the microscopic theory of the homogeneous gas. In this paper, we first derive, via a diagrammatic expansion, the scaling structure near the phase transition in a homogeneous system, and then study the effects of a trapping potential in the local density approximation. We find that a weakly interacting trapped gas undergoes a Kosterlitz-Thouless-Berezinskii transition from the normal state at a temperature slightly below the Bose-Einstein transition temperature of the ideal gas. The characteristic finite superfluid mass density of a homogeneous system just below the transition becomes strongly suppressed in a trapped gas.

Response Functions for the Two-Dimensional Ultracold Fermi Gas: Dynamical BCS Theory and Beyond

NASA Astrophysics Data System (ADS)

Vitali, Ettore; Shi, Hao; Qin, Mingpu; Zhang, Shiwei

2017-12-01

Response functions are central objects in physics. They provide crucial information about the behavior of physical systems, and they can be directly compared with scattering experiments involving particles such as neutrons or photons. Calculations of such functions starting from the many-body Hamiltonian of a physical system are challenging and extremely valuable. In this paper, we focus on the two-dimensional (2D) ultracold Fermi atomic gas which has been realized experimentally. We present an application of the dynamical BCS theory to obtain response functions for different regimes of interaction strengths in the 2D gas with zero-range attractive interaction. We also discuss auxiliary-field quantum Monte Carlo (AFQMC) methods for the calculation of imaginary time correlations in these dilute Fermi gas systems. Illustrative results are given and comparisons are made between AFQMC and dynamical BCS theory results to assess the accuracy of the latter.

How can we probe the atom mass currents induced by synthetic gauge fields?

NASA Astrophysics Data System (ADS)

Paramekanti, Arun; Killi, Matthew; Trotzky, Stefan

2013-05-01

Ultracold atomic fermions and bosons in an optical lattice can have quantum ground states which support equilibrium currents in the presence of synthetic magnetic fields or spin orbit coupling. As a tool to uncover these mass currents, we propose using an anisotropic quantum quench of the optical lattice which dynamically converts the current patterns into measurable density patterns. Using analytical calculations and numerical simulations, we show that this scheme can probe diverse equilibrium bulk current patterns in Bose superfluids and Fermi fluids induced by synthetic magnetic fields, as well as detect the chiral edge currents in topological states of atomic matter such as quantum Hall and quantum spin Hall insulators. This work is supported by NSERC of Canada and the Canadian Institute for Advanced Research.

Scattering length of composite bosons in the three-dimensional BCS-BEC crossover

NASA Astrophysics Data System (ADS)

Salasnich, L.; Bighin, G.

2015-03-01

We study the zero-temperature grand potential of a three-dimensional superfluid made of ultracold fermionic alkali-metal atoms in the BCS-BEC crossover. In particular, we analyze the zero-point energy of both fermionic single-particle excitations and bosonic collective excitations. The bosonic elementary excitations, which are crucial to obtain a reliable equation of state in the Bose-Einstein condensate regime, are obtained with a low-momentum expansion up to the forth order of the quadratic (Gaussian) action of the fluctuating pairing field. By performing a cutoff regularization and renormalization of Gaussian fluctuations, we find that the scattering length aB of composite bosons, bound states of fermionic pairs, is given by aB=(2 /3 ) aF , where aF is the scattering length of fermions.

Synthetic Unruh effect in cold atoms

NASA Astrophysics Data System (ADS)

Rodríguez-Laguna, Javier; Tarruell, Leticia; Lewenstein, Maciej; Celi, Alessio

2017-01-01

We propose to simulate a Dirac field near an event horizon using ultracold atoms in an optical lattice. Such a quantum simulator allows for the observation of the celebrated Unruh effect. Our proposal involves three stages: (1) preparation of the ground state of a massless two-dimensional Dirac field in Minkowski space-time; (2) quench of the optical lattice setup to simulate how an accelerated observer would view that state; (3) measurement of the local quantum fluctuation spectra by one-particle excitation spectroscopy in order to simulate a De Witt detector. According to Unruh's prediction, fluctuations measured in such a way must be thermal. Moreover, following Takagi's inversion theorem, they will obey the Bose-Einstein distribution, which will smoothly transform into the Fermi-Dirac as one of the dimensions of the lattice is reduced.

Solvable Hydrodynamics of Quantum Integrable Systems

NASA Astrophysics Data System (ADS)

Bulchandani, Vir B.; Vasseur, Romain; Karrasch, Christoph; Moore, Joel E.

2017-12-01

The conventional theory of hydrodynamics describes the evolution in time of chaotic many-particle systems from local to global equilibrium. In a quantum integrable system, local equilibrium is characterized by a local generalized Gibbs ensemble or equivalently a local distribution of pseudomomenta. We study time evolution from local equilibria in such models by solving a certain kinetic equation, the "Bethe-Boltzmann" equation satisfied by the local pseudomomentum density. Explicit comparison with density matrix renormalization group time evolution of a thermal expansion in the XXZ model shows that hydrodynamical predictions from smooth initial conditions can be remarkably accurate, even for small system sizes. Solutions are also obtained in the Lieb-Liniger model for free expansion into vacuum and collisions between clouds of particles, which model experiments on ultracold one-dimensional Bose gases.

On the number of Bose-selected modes in driven-dissipative ideal Bose gases

NASA Astrophysics Data System (ADS)

Schnell, Alexander; Ketzmerick, Roland; Eckardt, André

2018-03-01

In an ideal Bose gas that is driven into a steady state far from thermal equilibrium, a generalized form of Bose condensation can occur. Namely, the single-particle states unambiguously separate into two groups: the group of Bose-selected states, whose occupations increase linearly with the total particle number, and the group of all other states whose occupations saturate [Phys. Rev. Lett. 111, 240405 (2013), 10.1103/PhysRevLett.111.240405]. However, so far very little is known about how the number of Bose-selected states depends on the properties of the system and its coupling to the environment. The answer to this question is crucial since systems hosting a single, a few, or an extensive number of Bose-selected states will show rather different behavior. While in the former two scenarios each selected mode acquires a macroscopic occupation, corresponding to (fragmented) Bose condensation, the latter case rather bears resemblance to a high-temperature state of matter. In this paper, we systematically investigate the number of Bose-selected states, considering different classes of the rate matrices that characterize the driven-dissipative ideal Bose gases in the limit of weak system-bath coupling. These include rate matrices with continuum limit, rate matrices of chaotic driven systems, random rate matrices, and rate matrices resulting from thermal baths that couple to a few observables only.

On the number of Bose-selected modes in driven-dissipative ideal Bose gases.

PubMed

Schnell, Alexander; Ketzmerick, Roland; Eckardt, André

2018-03-01

In an ideal Bose gas that is driven into a steady state far from thermal equilibrium, a generalized form of Bose condensation can occur. Namely, the single-particle states unambiguously separate into two groups: the group of Bose-selected states, whose occupations increase linearly with the total particle number, and the group of all other states whose occupations saturate [Phys. Rev. Lett. 111, 240405 (2013)PRLTAO0031-900710.1103/PhysRevLett.111.240405]. However, so far very little is known about how the number of Bose-selected states depends on the properties of the system and its coupling to the environment. The answer to this question is crucial since systems hosting a single, a few, or an extensive number of Bose-selected states will show rather different behavior. While in the former two scenarios each selected mode acquires a macroscopic occupation, corresponding to (fragmented) Bose condensation, the latter case rather bears resemblance to a high-temperature state of matter. In this paper, we systematically investigate the number of Bose-selected states, considering different classes of the rate matrices that characterize the driven-dissipative ideal Bose gases in the limit of weak system-bath coupling. These include rate matrices with continuum limit, rate matrices of chaotic driven systems, random rate matrices, and rate matrices resulting from thermal baths that couple to a few observables only.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kira, M., E-mail: mackillo.kira@physik.uni-marburg.de

Atomic Bose–Einstein condensates (BECs) can be viewed as macroscopic objects where atoms form correlated atom clusters to all orders. Therefore, the presence of a BEC makes the direct use of the cluster-expansion approach–lucrative e.g. in semiconductor quantum optics–inefficient when solving the many-body kinetics of a strongly interacting Bose. An excitation picture is introduced with a nonunitary transformation that describes the system in terms of atom clusters within the normal component alone. The nontrivial properties of this transformation are systematically studied, which yields a cluster-expansion friendly formalism for a strongly interacting Bose gas. Its connections and corrections to the standard Hartree–Fock–Bogoliubov approachmore » are discussed and the role of the order parameter and the Bogoliubov excitations are identified. The resulting interaction effects are shown to visibly modify number fluctuations of the BEC. Even when the BEC has a nearly perfect second-order coherence, the BEC number fluctuations can still resolve interaction-generated non-Poissonian fluctuations. - Highlights: • Excitation picture expresses interacting Bose gas with few atom clusters. • Semiconductor and BEC many-body investigations are connected with cluster expansion. • Quantum statistics of BEC is identified in terms of atom clusters. • BEC number fluctuations show extreme sensitivity to many-body correlations. • Cluster-expansion friendly framework is established for an interacting Bose gas.« less

Atom-chip-based interferometry with Bose-Einstein condensates

NASA Astrophysics Data System (ADS)

Gebbe, Martina; Abend, Sven; Gersemann, Matthias; Ahlers, Holger; Muentinga, Hauke; Herrmann, Sven; Laemmerzahl, Claus; Ertmer, Wolfgang; Rasel, Ernst M.; Quantus Collaboration

2017-04-01

Due to their small spatial and momentum width ultracold Bose-Einstein condensates (BEC) or even delta-kick collimated (DKC) atomic ensembles are very well suited for high precision atom interferometry and measure, for example, inertial forces with high accuracy. We generate such an ensemble in a miniaturized atom-chip setup, where BEC generation and DKC can be performed in a fast and reliable way. Using the chip as a retroreflector we have realized the first atom-chip-based gravimeter. All atom-optical operations including detection take place inside a volume of a one centimeter cube. In order to investigate new geometries we studied symmetric double Bragg diffraction as well as the coherent acceleration of atoms with Bloch oscillations. By combining both techniques we developed a novel relaunch mechanism, which we use to span a fountain geometry within our gravimeter. The relaunch increases the free fall time and, thus, enhances the device's sensitivity. Additionally, we employ these techniques to implement symmetric scalable large momentum beam splitters. This work is supported by the CRC 1128 geo-Q and the DLR with funds provided by the Federal Ministry of Economic Affairs and Energy (BMWi) due to an enactment of the German Bundestag under Grant No. DLR 50WM1552-1557 (QUANTUS-IV-Fallturm).

Bose-Einstein condensation of spin wave quanta at room temperature.

PubMed

Dzyapko, O; Demidov, V E; Melkov, G A; Demokritov, S O

2011-09-28

Spin waves are delocalized excitations of magnetic media that mainly determine their magnetic dynamics and thermodynamics at temperatures far below the critical one. The quantum-mechanical counterparts of spin waves are magnons, which can be considered as a gas of weakly interacting bosonic quasi-particles. Here, we discuss the room-temperature kinetics and thermodynamics of the magnon gas in yttrium iron garnet films driven by parametric microwave pumping. We show that for high enough pumping powers, the thermalization of the driven gas results in a quasi-equilibrium state described by Bose-Einstein statistics with a non-zero chemical potential. Further increases of the pumping power cause a Bose-Einstein condensation documented by an observation of the magnon accumulation at the lowest energy level. Using the sensitivity of the Brillouin light scattering spectroscopy to the degree of coherence of the scattering magnons, we confirm the spontaneous emergence of coherence of the magnons accumulated at the bottom of the spectrum, occurring if their density exceeds a critical value.

Condensate fluctuations of interacting Bose gases within a microcanonical ensemble.

PubMed

Wang, Jianhui; He, Jizhou; Ma, Yongli

2011-05-01

Based on counting statistics and Bogoliubov theory, we present a recurrence relation for the microcanonical partition function for a weakly interacting Bose gas with a finite number of particles in a cubic box. According to this microcanonical partition function, we calculate numerically the distribution function, condensate fraction, and condensate fluctuations for a finite and isolated Bose-Einstein condensate. For ideal and weakly interacting Bose gases, we compare the condensate fluctuations with those in the canonical ensemble. The present approach yields an accurate account of the condensate fluctuations for temperatures close to the critical region. We emphasize that the interactions between excited atoms turn out to be important for moderate temperatures.

The BCS-BEC crossover: From ultra-cold Fermi gases to nuclear systems

NASA Astrophysics Data System (ADS)

Strinati, Giancarlo Calvanese; Pieri, Pierbiagio; Röpke, Gerd; Schuck, Peter; Urban, Michael

2018-04-01

This report addresses topics and questions of common interest in the fields of ultra-cold gases and nuclear physics in the context of the BCS-BEC crossover. By this crossover, the phenomena of Bardeen-Cooper-Schrieffer (BCS) superfluidity and Bose-Einstein condensation (BEC), which share the same kind of spontaneous symmetry breaking, are smoothly connected through the progressive reduction of the size of the fermion pairs involved as the fundamental entities in both phenomena. This size ranges, from large values when Cooper pairs are strongly overlapping in the BCS limit of a weak inter-particle attraction, to small values when composite bosons are non-overlapping in the BEC limit of a strong inter-particle attraction, across the intermediate unitarity limit where the size of the pairs is comparable with the average inter-particle distance. The BCS-BEC crossover has recently been realized experimentally, and essentially in all of its aspects, with ultra-cold Fermi gases. This realization, in turn, has raised the interest of the nuclear physics community in the crossover problem, since it represents an unprecedented tool to test fundamental and unanswered questions of nuclear many-body theory. Here, we focus on the several aspects of the BCS-BEC crossover, which are of broad joint interest to both ultra-cold Fermi gases and nuclear matter, and which will likely help to solve in the future some open problems in nuclear physics (concerning, for instance, neutron stars). Similarities and differences occurring in ultra-cold Fermi gases and nuclear matter will then be emphasized, not only about the relative phenomenologies but also about the theoretical approaches to be used in the two contexts. Common to both contexts is the fact that at zero temperature the BCS-BEC crossover can be described at the mean-field level with reasonable accuracy. At finite temperature, on the other hand, inclusion of pairing fluctuations beyond mean field represents an essential ingredient of the theory, especially in the normal phase where they account for precursor pairing effects. After an introduction to present the key concepts of the BCS-BEC crossover, this report discusses the mean-field treatment of the superfluid phase, both for homogeneous and inhomogeneous systems, as well as for symmetric (spin- or isospin-balanced) and asymmetric (spin- or isospin-imbalanced) matter. Pairing fluctuations in the normal phase are then considered, with their manifestations in thermodynamic and dynamic quantities. The last two Sections provide a more specialized discussion of the BCS-BEC crossover in ultra-cold Fermi gases and nuclear matter, respectively. The separate discussion in the two contexts aims at cross communicating to both communities topics and aspects which, albeit arising in one of the two fields, share a strong common interest.

Fluctuation-induced forces in confined ideal and imperfect Bose gases

NASA Astrophysics Data System (ADS)

Diehl, H. W.; Rutkevich, Sergei B.

2017-06-01

Fluctuation-induced ("Casimir") forces caused by thermal and quantum fluctuations are investigated for ideal and imperfect Bose gases confined to d -dimensional films of size ∞d -1×D under periodic (P), antiperiodic (A), Dirichlet-Dirichlet (DD), Neumann-Neumann (NN), and Robin (R) boundary conditions (BCs). The full scaling functions ΥdBC(xλ=D /λth ,xξ=D /ξ ) of the residual reduced grand potential per area φres,dBC(T ,μ ,D ) =D-(d -1 )ΥdBC(xλ,xξ) are determined for the ideal gas case with these BCs, where λth and ξ are the thermal de Broglie wavelength and the bulk correlation length, respectively. The associated limiting scaling functions ΘdBC(xξ) ≡ΥdBC(∞ ,xξ) describing the critical behavior at the bulk condensation transition are shown to agree with those previously determined from a massive free O (2 ) theory for BC=P,A,DD,DN,NN . For d =3 , they are expressed in closed analytical form in terms of polylogarithms. The analogous scaling functions ΥdBC(xλ,xξ,c1D ,c2D ) and ΘdR(xξ,c1D ,c2D ) under the RBCs (∂z-c1) ϕ |z=0=(∂z+c2) ϕ | z =D=0 with c1≥0 and c2≥0 are also determined. The corresponding scaling functions Υ∞,d P(xλ,xξ) and Θ∞,d P(xξ) for the imperfect Bose gas are shown to agree with those of the interacting Bose gas with n internal degrees of freedom in the limit n →∞ . Hence, for d =3 , Θ∞,d P(xξ) is known exactly in closed analytic form. To account for the breakdown of translation invariance in the direction perpendicular to the boundary planes implied by free BCs such as DDBCs, a modified imperfect Bose gas model is introduced that corresponds to the limit n →∞ of this interacting Bose gas. Numerically and analytically exact results for the scaling function Θ∞,3 DD(xξ) therefore follow from those of the O (2 n ) ϕ4 model for n →∞ .

Fluctuation-induced forces in confined ideal and imperfect Bose gases.

PubMed

Diehl, H W; Rutkevich, Sergei B

2017-06-01

Fluctuation-induced ("Casimir") forces caused by thermal and quantum fluctuations are investigated for ideal and imperfect Bose gases confined to d-dimensional films of size ∞^{d-1}×D under periodic (P), antiperiodic (A), Dirichlet-Dirichlet (DD), Neumann-Neumann (NN), and Robin (R) boundary conditions (BCs). The full scaling functions Υ_{d}^{BC}(x_{λ}=D/λ_{th},x_{ξ}=D/ξ) of the residual reduced grand potential per area φ_{res,d}^{BC}(T,μ,D)=D^{-(d-1)}Υ_{d}^{BC}(x_{λ},x_{ξ}) are determined for the ideal gas case with these BCs, where λ_{th} and ξ are the thermal de Broglie wavelength and the bulk correlation length, respectively. The associated limiting scaling functions Θ_{d}^{BC}(x_{ξ})≡Υ_{d}^{BC}(∞,x_{ξ}) describing the critical behavior at the bulk condensation transition are shown to agree with those previously determined from a massive free O(2) theory for BC=P,A,DD,DN,NN. For d=3, they are expressed in closed analytical form in terms of polylogarithms. The analogous scaling functions Υ_{d}^{BC}(x_{λ},x_{ξ},c_{1}D,c_{2}D) and Θ_{d}^{R}(x_{ξ},c_{1}D,c_{2}D) under the RBCs (∂_{z}-c_{1})ϕ|_{z=0}=(∂_{z}+c_{2})ϕ|_{z=D}=0 with c_{1}≥0 and c_{2}≥0 are also determined. The corresponding scaling functions Υ_{∞,d}^{P}(x_{λ},x_{ξ}) and Θ_{∞,d}^{P}(x_{ξ}) for the imperfect Bose gas are shown to agree with those of the interacting Bose gas with n internal degrees of freedom in the limit n→∞. Hence, for d=3, Θ_{∞,d}^{P}(x_{ξ}) is known exactly in closed analytic form. To account for the breakdown of translation invariance in the direction perpendicular to the boundary planes implied by free BCs such as DDBCs, a modified imperfect Bose gas model is introduced that corresponds to the limit n→∞ of this interacting Bose gas. Numerically and analytically exact results for the scaling function Θ_{∞,3}^{DD}(x_{ξ}) therefore follow from those of the O(2n)ϕ^{4} model for n→∞.

Superstatistical Energy Distributions of an Ion in an Ultracold Buffer Gas

NASA Astrophysics Data System (ADS)

Rouse, I.; Willitsch, S.

2017-04-01

An ion in a radio frequency ion trap interacting with a buffer gas of ultracold neutral atoms is a driven dynamical system which has been found to develop a nonthermal energy distribution with a power law tail. The exact analytical form of this distribution is unknown, but has often been represented empirically by q -exponential (Tsallis) functions. Based on the concepts of superstatistics, we introduce a framework for the statistical mechanics of an ion trapped in an rf field subject to collisions with a buffer gas. We derive analytic ion secular energy distributions from first principles both neglecting and including the effects of the thermal energy of the buffer gas. For a buffer gas with a finite temperature, we prove that Tsallis statistics emerges from the combination of a constant heating term and multiplicative energy fluctuations. We show that the resulting distributions essentially depend on experimentally controllable parameters paving the way for an accurate control of the statistical properties of ion-atom hybrid systems.

Fast and accurate calculation of dilute quantum gas using Uehling–Uhlenbeck model equation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yano, Ryosuke, E-mail: ryosuke.yano@tokiorisk.co.jp

The Uehling–Uhlenbeck (U–U) model equation is studied for the fast and accurate calculation of a dilute quantum gas. In particular, the direct simulation Monte Carlo (DSMC) method is used to solve the U–U model equation. DSMC analysis based on the U–U model equation is expected to enable the thermalization to be accurately obtained using a small number of sample particles and the dilute quantum gas dynamics to be calculated in a practical time. Finally, the applicability of DSMC analysis based on the U–U model equation to the fast and accurate calculation of a dilute quantum gas is confirmed by calculatingmore » the viscosity coefficient of a Bose gas on the basis of the Green–Kubo expression and the shock layer of a dilute Bose gas around a cylinder.« less

Hyperspherical lowest-order constrained-variational approximation to resonant Bose-Einstein condensates

NASA Astrophysics Data System (ADS)

Sze, M. W. C.; Sykes, A. G.; Blume, D.; Bohn, J. L.

2018-03-01

We study the ground-state properties of a system of N harmonically trapped bosons of mass m interacting with two-body contact interactions, from small to large scattering lengths. This is accomplished in a hyperspherical coordinate system that is flexible enough to describe both the overall scale of the gas and two-body correlations. By adapting the lowest-order constrained-variational method, we are able to semiquantitatively attain Bose-Einstein condensate ground-state energies even for gases with infinite scattering length. In the large-particle-number limit, our method provides analytical estimates for the energy per particle E0/N ≈2.5 N1 /3ℏ ω and two-body contact C2/N ≈16 N1 /6√{m ω /ℏ } for a Bose gas on resonance, where ω is the trap frequency.

SISGR: Atom chip microscopy: A novel probe for strongly correlated materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lev, Benjamin L.

Microscopy techniques co-opted from nonlinear optics and high energy physics have complemented solid-state probes in elucidating the order manifest in condensed matter materials. Up until now, however, no attempts have been made to use modern techniques of ultracold atomic physics to directly explore properties of strongly correlated or topologically protected materials. Our current program is focused on introducing a novel magnetic field microscopy technique into the toolbox of imaging probes. Our prior DOE ESPM program funded the development of a novel instrument using a dilute gas Bose-Einstein condensate (BEC) as a scanning probe capable of measuring tiny magnetic (and electric)more » DC and AC fields above materials. We successfully built the world's first “scanning cryogenic atom chip microscope” [1], and we now are in the process of characterizing its performance before using the instrument to take the first wide-area images of transport flow within unconventional superconductors, pnictides and oxide interfaces (LAO/STO), topological insulators, and colossal magnetoresistive manganites. We will do so at temperatures outside the capability of scanning SQUIDs, with ~10x better resolution and without 1/f-noise. A notable goal will be to measure the surface-to-bulk conductivity ratio in topological insulators in a relatively model-independent fashion [2]. We have completed the construction of this magnetic microscope, shown in Figure 1. The instrument uses atom chips—substrates supporting micron-sized current-carrying wires that create magnetic microtraps near surfaces for ultracold thermal gases and BECs—to enable single-shot and raster-scanned large-field-of-view detection of magnetic fields. The fields emanating from electronic transport may be detected at the 10-7 flux quantum (Φ0) level and below (see Fig. 2); that is, few to sub-micron resolution of sub-nanotesla fields over single-shot, millimeter-long detection lengths. By harnessing the extreme sensitivity of atomic clocks and BECs to external perturbations, we are now in a position to use atom chips for imaging transport in new regimes. Scanning quantum gas atom chip microscopy introduces three very important features to the toolbox of high-resolution scanning microscopy of strongly correlated or topological materials: simultaneous detection of magnetic and electric fields (down to the sub-single electron charge level [3,4]; no invasive large magnetic fields or gradients; simultaneous micro- and macroscopic spatial resolution; DC to MHz detection bandwidth; freedom from 1/f flicker noise at low frequencies; and, perhaps most importantly, the complete decoupling of probe and sample temperatures. The atom chip microscope can operate at maximum sensitivity and resolution without regard to the substrate temperature. While the BEC is among the coldest objects realizable (100 nK temperatures are typical), the atom chip substrate can be positioned 1 μm away from the BEC and be as hot as 400 K or as cold as the cryostat can cool. This is because unlike superconducting probes, whose temperature is closely coupled to nearby materials, quantum gases are immune to radiative heating. The energy gap between a Rb atom’s ground state and first excited state far exceeds the typical energy of room-temperature blackbody radiation; such atoms are therefore transparent to radiation heating by materials at room temperature or below. We experimentally demonstrated a new atom chip trapping system that allows the placement and high-resolution imaging of ultracold atoms within microns from any ≤100 μm-thin, UHV-compatible material, while also allowing sample exchange with minimal experimental downtime [1]. The sample is not connected to the atom chip, allowing rapid exchange without perturbing the atom chip or laser cooling apparatus. Exchange of the sample and retrapping of atoms has been performed within a week turnaround, limited only by chamber baking. Moreover, the decoupling of sample and atom chip provides the ability to independently tune the sample temperature and its position with respect to the trapped ultracold gas, which itself may remain in the focus of a high-resolution imaging system. See Fig. 3. We confine 100-nK BECs of 104 87Rb atoms near a gold-mirrored 100-μm-thick silicon substrate. The substrate can be cooled to 35 K without use of a heat shield, while the atom chip, 120-μm away, remains at room temperature. Atoms may be imaged with 1-μm resolution and retrapped every 16 s, allowing rapid data collection. Straightforward improvements will allow us to push sample temperatures close to 4 K, and improve imaging resolution from 1 μm down to a few-100 nm, thereby providing 10-9 Φ0 detection sensitivity. We will test the utility of this technique by imaging the magnetic fields emanating from electronic transport and domain percolation in several interesting examples of strongly correlated or topologically protected materials. STM, transport, and x-ray scattering experiments have, among others, revealed the existence of a quantum liquid crystal state in iron (pnictide) and cuprate superconductors. This strongly correlated state of matter could also be detected by imaging the fluctuating transport (spatially and in time) of electrons as the phase/regime boundary is crossed between the pnictide non-Fermi liquid (cuprate strange metal) and the pnictide magnetic phase (cuprate pseudogap regime). Our ability to image wide-area inhomogeneous current flow from room-temperature to <10 K will allow us to study the developing domain structure and transport near twin boundary interfaces through the TN~50-150 K nematic transition recently identified in bulk transport experiments by Ian Fisher's group in underdoped Fe-arsinide superconductors [6]. Again, this highlights a main feature of our cryogenic atom chip microscope: the ability to image transport regardless of the sample temperature since the BEC, at nK temperatures, is transparent to blackbody radiation, even when held a microns from the surface. References: 3) S. Aigner et al., Long-range order in electronic transport through disordered metal films, Science 319 319 (2008). 4) S. Wildermuth, et al. Sensing electric and magnetic fields with Bose-Einstein condensates, Appl. Phys. Lett. 88, 264103 (2006). 5) M. Lu, N. Q. Burdick, S.-H. Youn, and B. L. Lev, Strongly Dipolar Bose-Einstein Condensate of Dysprosium, PRL 107, 190401 (2011). 6) J.-H. Chu, J. Analytis, K. De Greve, P. Mcmahon, A. Islam, Y. Yamamoto, and I. Fisher, In-Plane Resistivity Anisotropy in an Underdoped Iron Arsenide Superconductor, Science 329, 824 (2010). Publications: 1) M. A. Naides, R. W. Turner, R. A. Lai, J. M. DiSciacca, and B. L. Lev, Trapping ultracold gases near cryogenic materials with rapid reconfigurability, Applied Physics Letters 103, 251112 (2013). 2) B. Dellabetta, T. L. Hughes, M. J. Gilbert, and B. L. Lev, Imaging topologically protected transport with quantum degenerate gases, Phys. Rev. B 85, 205442 (2012).« less

Temperature Dependence of the Thermal Conductivity of a Trapped Dipolar Bose-Condensed Gas

NASA Astrophysics Data System (ADS)

Yavari, H.

2018-02-01

The thermal conductivity of a trapped dipolar Bose condensed gas is calculated as a function of temperature in the framework of linear response theory. The contributions of the interactions between condensed and noncondensed atoms and between noncondensed atoms in the presence of both contact and dipole-dipole interactions are taken into account to the thermal relaxation time, by evaluating the self-energies of the system in the Beliaev approximation. We will show that above the Bose-Einstein condensation temperature ( T > T BEC ) in the absence of dipole-dipole interaction, the temperature dependence of the thermal conductivity reduces to that of an ideal Bose gas. In a trapped Bose-condensed gas for temperature interval k B T << n 0 g B , E p << k B T ( n 0 is the condensed density and g B is the strength of the contact interaction), the relaxation rates due to dipolar and contact interactions between condensed and noncondensed atoms change as {τ}_{dd12}^{-1}∝ {e}^{-E/{k}_BT} and τ c12 ∝ T -5, respectively, and the contact interaction plays the dominant role in the temperature dependence of the thermal conductivity, which leads to the T -3 behavior of the thermal conductivity. In the low-temperature limit, k B T << n 0 g B , E p >> k B T, since the relaxation rate {τ}_{c12}^{-1} is independent of temperature and the relaxation rate due to dipolar interaction goes to zero exponentially, the T 2 temperature behavior for the thermal conductivity comes from the thermal mean velocity of the particles. We will also show that in the high-temperature limit ( k B T > n 0 g B ) and low momenta, the relaxation rates {τ}_{c12}^{-1} and {τ}_{dd12}^{-1} change linearly with temperature for both dipolar and contact interactions and the thermal conductivity scales linearly with temperature.

Strong photoassociation in a degenerate fermi gas

NASA Astrophysics Data System (ADS)

Rvachov, Timur; Jamison, Alan; Jing, Li; Son, Hyungmok; Ebadi, Sepehr; Jiang, Yijun; Zwierlein, Martin; Ketterle, Wolfgang

2016-05-01

Despite many studies there remain open questions about strong photoassociation in ultracold gases. We study the effects of strong photoassociation in ultracold fermions. Photoassociation occurs only at short range and thus can be used as a tool to probe and control the two-body correlation function in an interacting many-body system. We study the effects of strong photoassociation in 6 Li, the onset of saturation, and its effects on spin polarized and interacting spin-mixtures. This work was funded by the NSF, ARO-MURI, SAMSUNG, and NSERC.

Spatial shaping for generating arbitrary optical dipole traps for ultracold degenerate gases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Jeffrey G., E-mail: jglee@umd.edu; Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742; Hill, W. T., E-mail: wth@umd.edu

2014-10-15

We present two spatial-shaping approaches – phase and amplitude – for creating two-dimensional optical dipole potentials for ultracold neutral atoms. When combined with an attractive or repulsive Gaussian sheet formed by an astigmatically focused beam, atoms are trapped in three dimensions resulting in planar confinement with an arbitrary network of potentials – a free-space atom chip. The first approach utilizes an adaptation of the generalized phase-contrast technique to convert a phase structure embedded in a beam after traversing a phase mask, to an identical intensity profile in the image plane. Phase masks, and a requisite phase-contrast filter, can be chemicallymore » etched into optical material (e.g., fused silica) or implemented with spatial light modulators; etching provides the highest quality while spatial light modulators enable prototyping and realtime structure modification. This approach was demonstrated on an ensemble of thermal atoms. Amplitude shaping is possible when the potential structure is made as an opaque mask in the path of a dipole trap beam, followed by imaging the shadow onto the plane of the atoms. While much more lossy, this very simple and inexpensive approach can produce dipole potentials suitable for containing degenerate gases. High-quality amplitude masks can be produced with standard photolithography techniques. Amplitude shaping was demonstrated on a Bose-Einstein condensate.« less

Quench dynamics of the interacting Bose gas in one dimension.

PubMed

Iyer, Deepak; Andrei, Natan

2012-09-14

We obtain an exact expression for the time evolution of the interacting Bose gas following a quench from a generic initial state using the Yudson representation for integrable systems. We study the time evolution of the density and noise correlation for a small number of bosons and their asymptotic behavior for any number. We show that for any value of the coupling, as long as it is repulsive, the system asymptotes towards a strongly repulsive gas, while for any value of an attractive coupling the long time behavior is dominated by the maximal bound state. This occurs independently of the initial state and can be viewed as an emerging "dynamic universality."

Coherent magnon optics in a ferromagnetic spinor Bose-Einstein condensate.

PubMed

Marti, G Edward; MacRae, Andrew; Olf, Ryan; Lourette, Sean; Fang, Fang; Stamper-Kurn, Dan M

2014-10-10

We measure the dispersion relation, gap, and magnetic moment of a magnon in the ferromagnetic F = 1 spinor Bose-Einstein condensate of (87)Rb. From the dispersion relation we measure an average effective mass 1.033(2)(stat)(10)(sys) times the atomic mass, as determined by interfering standing and running coherent magnon waves within the dense and trapped condensed gas. The measured mass is higher than theoretical predictions of mean-field and beyond-mean-field Beliaev theory for a bulk spinor Bose gas with s-wave contact interactions. We observe a magnon energy gap of h × 2.5(1)(stat)(2)(sys) Hz, which is consistent with the predicted effect of magnetic dipole-dipole interactions. These dipolar interactions may also account for the high magnon mass. The effective magnetic moment of -1.04(2)(stat)(8)(sys) times the atomic magnetic moment is consistent with mean-field theory.

Bose polaron problem: Effect of mass imbalance on binding energy

NASA Astrophysics Data System (ADS)

Ardila, L. A. Peña; Giorgini, S.

2016-12-01

By means of quantum Monte Carlo methods we calculate the binding energy of an impurity immersed in a Bose-Einstein condensate at T =0 . The focus is on the attractive branch of the Bose polaron and on the role played by the mass imbalance between the impurity and the surrounding particles. For an impurity resonantly coupled to the bath, we investigate the dependence of the binding energy on the mass ratio and on the interaction strength within the medium. In particular, we determine the equation of state in the case of a static (infinite mass) impurity, where three-body correlations are irrelevant and the result is expected to be a universal function of the gas parameter. For the mass ratio corresponding to 40K impurities in a gas of 87Rb atoms, we provide an explicit comparison with the experimental findings of a recent study carried out at JILA.

Solving the Quantum Many-Body Problem via Correlations Measured with a Momentum Microscope

NASA Astrophysics Data System (ADS)

Hodgman, S. S.; Khakimov, R. I.; Lewis-Swan, R. J.; Truscott, A. G.; Kheruntsyan, K. V.

2017-06-01

In quantum many-body theory, all physical observables are described in terms of correlation functions between particle creation or annihilation operators. Measurement of such correlation functions can therefore be regarded as an operational solution to the quantum many-body problem. Here, we demonstrate this paradigm by measuring multiparticle momentum correlations up to third order between ultracold helium atoms in an s -wave scattering halo of colliding Bose-Einstein condensates, using a quantum many-body momentum microscope. Our measurements allow us to extract a key building block of all higher-order correlations in this system—the pairing field amplitude. In addition, we demonstrate a record violation of the classical Cauchy-Schwarz inequality for correlated atom pairs and triples. Measuring multiparticle momentum correlations could provide new insights into effects such as unconventional superconductivity and many-body localization.

Analytical pair correlations in ideal quantum gases: temperature-dependent bunching and antibunching.

PubMed

Bosse, J; Pathak, K N; Singh, G S

2011-10-01

The fluctuation-dissipation theorem together with the exact density response spectrum for ideal quantum gases has been utilized to yield a new expression for the static structure factor, which we use to derive exact analytical expressions for the temperature-dependent pair distribution function g(r) of the ideal gases. The plots of bosonic and fermionic g(r) display "Bose pile" and "Fermi hole" typically akin to bunching and antibunching as observed experimentally for ultracold atomic gases. The behavior of spin-scaled pair correlation for fermions is almost featureless, but bosons show a rich structure including long-range correlations near T(c). The coherent state at T=0 shows no correlation at all, just like single-mode lasers. The depicted decreasing trend in correlation with decrease in temperature for T

Evolution from Rydberg gas to ultracold plasma in a supersonic atomic beam of Xe

NASA Astrophysics Data System (ADS)

Hung, J.; Sadeghi, H.; Schulz-Weiling, M.; Grant, E. R.

2014-08-01

A Rydberg gas of xenon, entrained in a supersonic atomic beam, evolves slowly to form an ultracold plasma. In the early stages of this evolution, when the free-electron density is low, Rydberg atoms undergo long-range \\ell -mixing collisions, yielding states of high orbital angular momentum. The development of high-\\ell states promotes dipole-dipole interactions that help to drive Penning ionization. The electron density increases until it reaches the threshold for avalanche. Ninety μs after the production of a Rydberg gas with the initial state, {{n}_{0}}{{\\ell }_{0}}=42d, a 432 V cm-1 electrostatic pulse fails to separate charge in the excited volume, an effect which is ascribed to screening by free electrons. Photoexcitation cross sections, observed rates of \\ell -mixing, and a coupled-rate-equation model simulating the onset of the electron-impact avalanche point consistently to an initial Rydberg gas density of 5\\times {{10}^{8}}\\;c{{m}^{-3}}.

Potential Engineering of Fermi-Hubbard Systems using a Quantum Gas Microscope

NASA Astrophysics Data System (ADS)

Ji, Geoffrey; Mazurenko, Anton; Chiu, Christie; Parsons, Maxwell; Kanász-Nagy, Márton; Schmidt, Richard; Grusdt, Fabian; Demler, Eugene; Greif, Daniel; Greiner, Markus

2017-04-01

Arbitrary control of optical potentials has emerged as an important tool in manipulating ultracold atomic systems, especially when combined with the single-site addressing afforded by quantum gas microscopy. Already, experiments have used digital micromirror devices (DMDs) to initialize and control ultracold atomic systems in the context of studying quantum walks, quantum thermalization, and many-body localization. Here, we report on progress in using a DMD located in the image plane of a quantum gas microscope to explore static and dynamic properties of a 2D Fermi-Hubbard system. By projecting a large, ring-shaped anti-confining potential, we demonstrate entropy redistribution and controlled doping of the system. Moreover, we use the DMD to prepare localized holes, which upon release interact with and disrupt the surrounding spin environment. These techniques pave the way for controlled investigations of dynamics in the low-temperature phases of the Hubbard model.

Evidence of Antiblockade in an Ultracold Rydberg Gas

NASA Astrophysics Data System (ADS)

Amthor, Thomas; Giese, Christian; Hofmann, Christoph S.; Weidemüller, Matthias

2010-01-01

We present the experimental observation of the antiblockade in an ultracold Rydberg gas recently proposed by Ates et al. [Phys. Rev. Lett. 98, 023002 (2007)PRLTAO0031-900710.1103/PhysRevLett.98.023002]. Our approach allows the control of the pair distribution in the gas and is based on a strong coupling of one transition in an atomic three-level system, while introducing specific detunings of the other transition. When the coupling energy matches the interaction energy of the Rydberg long-range interactions, the otherwise blocked excitation of close pairs becomes possible. A time-resolved spectroscopic measurement of the Penning ionization signal is used to identify slight variations in the Rydberg pair distribution of a random arrangement of atoms. A model based on a pair interaction Hamiltonian is presented which well reproduces our experimental observations and allows one to deduce the distribution of nearest-neighbor distances.

Thermalization of a two-dimensional photonic gas in a `white wall' photon box

NASA Astrophysics Data System (ADS)

Klaers, Jan; Vewinger, Frank; Weitz, Martin

2010-07-01

Bose-Einstein condensation, the macroscopic accumulation of bosonic particles in the energetic ground state below a critical temperature, has been demonstrated in several physical systems. The perhaps best known example of a bosonic gas, blackbody radiation, however exhibits no Bose-Einstein condensation at low temperatures. Instead of collectively occupying the lowest energy mode, the photons disappear in the cavity walls when the temperature is lowered-corresponding to a vanishing chemical potential. Here we report on evidence for a thermalized two-dimensional photon gas with a freely adjustable chemical potential. Our experiment is based on a dye-filled optical microresonator, acting as a `white wall' box for photons. Thermalization is achieved in a photon-number-conserving way by photon scattering off the dye molecules, and the cavity mirrors provide both an effective photon mass and a confining potential-key prerequisites for the Bose-Einstein condensation of photons. As a striking example of the unusual system properties, we demonstrate a yet unobserved light concentration effect into the centre of the confining potential, an effect with prospects for increasing the efficiency of diffuse solar light collection.

Gravitational Thermodynamics for Interstellar Gas and Weakly Degenerate Quantum Gas

NASA Astrophysics Data System (ADS)

Zhu, Ding Yu; Shen, Jian Qi

2016-03-01

The temperature distribution of an ideal gas in gravitational fields has been identified as a longstanding problem in thermodynamics and statistical physics. According to the principle of entropy increase (i.e., the principle of maximum entropy), we apply a variational principle to the thermodynamical entropy functional of an ideal gas and establish a relationship between temperature gradient and gravitational field strength. As an illustrative example, the temperature and density distributions of an ideal gas in two simple but typical gravitational fields (i.e., a uniform gravitational field and an inverse-square gravitational field) are considered on the basis of entropic and hydrostatic equilibrium conditions. The effect of temperature inhomogeneity in gravitational fields is also addressed for a weakly degenerate quantum gas (e.g., Fermi and Bose gas). The present gravitational thermodynamics of a gas would have potential applications in quantum fluids, e.g., Bose-Einstein condensates in Earth’s gravitational field and the temperature fluctuation spectrum in cosmic microwave background radiation.

Bose-Einstein condensation of photons in a 'white-wall' photon box

NASA Astrophysics Data System (ADS)

Klärs, Jan; Schmitt, Julian; Vewinger, Frank; Weitz, Martin

2011-01-01

Bose-Einstein condensation, the macroscopic ground state occupation of a system of bosonic particles below a critical temperature, has been observed in cold atomic gases and solid-state physics quasiparticles. In contrast, photons do not show this phase transition usually, because in Planck's blackbody radiation the particle number is not conserved and at low temperature the photons disappear in the walls of the system. Here we report on the realization of a photon Bose-Einstein condensate in a dye-filled optical microcavity, which acts as a "white-wall" photon box. The cavity mirrors provide a trapping potential and a non-vanishing effective photon mass, making the system formally equivalent to a two-dimensional gas of trapped massive bosons. Thermalization of the photon gas is reached in a number conserving way by multiple scattering off the dye molecules. Signatures for a BEC upon increased photon density are: a spectral distribution that shows Bose-Einstein distributed photon energies with a macroscopically populated peak on top of a broad thermal wing, the observed threshold of the phase transition showing the predicted absolute value and scaling with resonator geometry, and condensation appearing at the trap centre even for a spatially displaced pump spot.

Landau instability and mobility edges of the interacting one-dimensional Bose gas in weak random potentials

NASA Astrophysics Data System (ADS)

Cherny, Alexander Yu; Caux, Jean-Sébastien; Brand, Joachim

2018-01-01

We study the frictional force exerted on the trapped, interacting 1D Bose gas under the influence of a moving random potential. Specifically we consider weak potentials generated by optical speckle patterns with finite correlation length. We show that repulsive interactions between bosons lead to a superfluid response and suppression of frictional force, which can inhibit the onset of Anderson localisation. We perform a quantitative analysis of the Landau instability based on the dynamic structure factor of the integrable Lieb-Liniger model and demonstrate the existence of effective mobility edges.

Non-equilibrium scale invariance and shortcuts to adiabaticity in a one-dimensional Bose gas

PubMed Central

Rohringer, W.; Fischer, D.; Steiner, F.; Mazets, I. E.; Schmiedmayer, J.; Trupke, M.

2015-01-01

We present experimental evidence for scale invariant behaviour of the excitation spectrum in phase-fluctuating quasi-1d Bose gases after a rapid change of the external trapping potential. Probing density correlations in free expansion, we find that the temperature of an initial thermal state scales with the spatial extension of the cloud as predicted by a model based on adiabatic rescaling of initial eigenmodes with conserved quasiparticle occupation numbers. Based on this result, we demonstrate that shortcuts to adiabaticity for the rapid expansion or compression of the gas do not induce additional heating. PMID:25867640

Monopole excitations of a harmonically trapped one-dimensional Bose gas from the ideal gas to the Tonks-Girardeau regime.

PubMed

Choi, S; Dunjko, V; Zhang, Z D; Olshanii, M

2015-09-11

Using a time-dependent modified nonlinear Schrödinger equation (MNLSE)-where the conventional chemical potential proportional to the density is replaced by the one inferred from Lieb-Liniger's exact solution-we study frequencies of the collective monopole excitations of a one-dimensional Bose gas. We find that our method accurately reproduces the results of a recent experimental study [E. Haller et al., Science 325, 1224 (2009)] in the full spectrum of interaction regimes from the ideal gas, through the mean-field regime, through the mean-field Thomas-Fermi regime, all the way to the Tonks-Giradeau gas. While the former two are accessible by the standard time-dependent NLSE and inaccessible by the time-dependent local density approximation, the situation reverses in the latter case. However, the MNLSE is shown to treat all these regimes within a single numerical method.

Universal Scaling Laws in the Dynamics of a Homogeneous Unitary Bose Gas

NASA Astrophysics Data System (ADS)

Eigen, Christoph; Glidden, Jake A. P.; Lopes, Raphael; Navon, Nir; Hadzibabic, Zoran; Smith, Robert P.

2017-12-01

We study the dynamics of an initially degenerate homogeneous Bose gas after an interaction quench to the unitary regime at a magnetic Feshbach resonance. As the cloud decays and heats, it exhibits a crossover from degenerate- to thermal-gas behavior, both of which are characterized by universal scaling laws linking the particle-loss rate to the total atom number N . In the degenerate and thermal regimes, the per-particle loss rate is ∝N2 /3 and N26 /9, respectively. The crossover occurs at a universal kinetic energy per particle and at a universal time after the quench, in units of energy and time set by the gas density. By slowly sweeping the magnetic field away from the resonance and creating a mixture of atoms and molecules, we also map out the dynamics of correlations in the unitary gas, which display a universal temporal scaling with the gas density, and reach a steady state while the gas is still degenerate.

Universal Scaling Laws in the Dynamics of a Homogeneous Unitary Bose Gas.

PubMed

Eigen, Christoph; Glidden, Jake A P; Lopes, Raphael; Navon, Nir; Hadzibabic, Zoran; Smith, Robert P

2017-12-22

We study the dynamics of an initially degenerate homogeneous Bose gas after an interaction quench to the unitary regime at a magnetic Feshbach resonance. As the cloud decays and heats, it exhibits a crossover from degenerate- to thermal-gas behavior, both of which are characterized by universal scaling laws linking the particle-loss rate to the total atom number N. In the degenerate and thermal regimes, the per-particle loss rate is ∝N^{2/3} and N^{26/9}, respectively. The crossover occurs at a universal kinetic energy per particle and at a universal time after the quench, in units of energy and time set by the gas density. By slowly sweeping the magnetic field away from the resonance and creating a mixture of atoms and molecules, we also map out the dynamics of correlations in the unitary gas, which display a universal temporal scaling with the gas density, and reach a steady state while the gas is still degenerate.

Renyi Entropy of the Ideal Gas in Finite Momentum Intervals

NASA Astrophysics Data System (ADS)

Bialas, A.; Czyz, W.

2003-06-01

Coincidence probabilities of multiparticle events, as measured in finite momentum intervals for Bose and Fermi ideal gas, are calculated and compared with the exact expressions given in statistical physics.

Bose gases near resonance: Renormalized interactions in a condensate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Fei, E-mail: feizhou@phas.ubc.ca; Mashayekhi, Mohammad S.

2013-01-15

Bose gases at large scattering lengths or beyond the usual dilute limit for a long time have been one of the most challenging problems in many-body physics. In this article, we investigate the fundamental properties of a near-resonance Bose gas and illustrate that three-dimensional Bose gases become nearly fermionized near resonance when the chemical potential as a function of scattering lengths reaches a maximum and the atomic condensates lose metastability. The instability and accompanying maximum are shown to be a precursor of the sign change of g{sub 2}, the renormalized two-body interaction between condensed atoms. g{sub 2} changes from effectivelymore » repulsive to attractive when approaching resonance from the molecular side, even though the scattering length is still positive. This occurs when dimers, under the influence of condensates, emerge at zero energy in the atomic gases at a finite positive scattering length. We carry out our studies of Bose gases via applying a self-consistent renormalization group equation which is further subject to a boundary condition. We also comment on the relation between the approach here and the diagrammatic calculation in an early article [D. Borzov, M.S. Mashayekhi, S. Zhang, J.-L. Song, F. Zhou, Phys. Rev. A 85 (2012) 023620]. - Highlights: Black-Right-Pointing-Pointer A Bose gas becomes nearly fermionized when its chemical potential approaches a maximum near resonance. Black-Right-Pointing-Pointer At the maximum, an onset instability sets in at a positive scattering length. Black-Right-Pointing-Pointer Condensates strongly influence the renormalization flow of few-body running coupling constants. Black-Right-Pointing-Pointer The effective two-body interaction constant changes its sign at a positive scattering length.« less

Equilibrium phases of dipolar lattice bosons in the presence of random diagonal disorder

NASA Astrophysics Data System (ADS)

Zhang, C.; Safavi-Naini, A.; Capogrosso-Sansone, B.

2018-01-01

Ultracold gases offer an unprecedented opportunity to engineer disorder and interactions in a controlled manner. In an effort to understand the interplay between disorder, dipolar interactions, and quantum degeneracy, we study two-dimensional hard-core dipolar lattice bosons in the presence of on-site bound disorder. Our results are based on large-scale path-integral quantum Monte Carlo simulations by the worm algorithm. We study the ground-state phase diagram at a fixed half-integer filling factor for which the clean system is either a superfluid at a lower dipolar interaction strength or a checkerboard solid at a larger dipolar interaction strength. We find that, even for weak dipolar interactions, superfluidity is destroyed in favor of a Bose glass at a relatively low disorder strength. Interestingly, in the presence of disorder, superfluidity persists for values of the dipolar interaction strength for which the clean system is a checkerboard solid. At a fixed disorder strength, as the dipolar interaction is increased, superfluidity is destroyed in favor of a Bose glass. As the interaction is further increased, the system eventually develops extended checkerboard patterns in the density distribution. Due to the presence of disorder, though, grain boundaries and defects, responsible for a finite residual compressibility, are present in the density distribution. Finally, we study the robustness of the superfluid phase against thermal fluctuations.

Chaoticity parameter λ in two-pion interferometry in an expanding boson gas model

DOE PAGES

Liu, Jie; Ru, Peng; Zhang, Wei-Ning; ...

2014-10-15

We investigate the chaoticity parameter λ in two-pion interferometry in an expanding boson gas model. The degree of Bose-Einstein condensation of identical pions, density distributions, and Hanbury-Brown-Twiss (HBT) correlation functions are calculated for the expanding gas within the mean-field description with a harmonic oscillator potential. The results indicate that a sources with thousands of identical pions may exhibit a degree of Bose-Einstein condensation at the temperatures during the hadronic phase in relativistic heavy-ion collisions. This finite condensation may decrease the chaoticity parameter λ in the two-pion interferometry measurements at low pion pair momenta, but influence only slightly the λ valuemore » at high pion pair momentum.« less

Creation of a strongly dipolar gas of ultracold ground-state 23 Na87 Rb molecules

NASA Astrophysics Data System (ADS)

Guo, Mingyang; Zhu, Bing; Lu, Bo; Ye, Xin; Wang, Fudong; Wang, Dajun; Vexiau, Romain; Bouloufa-Maafa, Nadia; Quéméner, Goulven; Dulieu, Olivier

2016-05-01

We report on successful creation of an ultracold sample of ground-state 23 Na87 Rb molecules with a large effective electric dipole moment. Through a carefully designed two-photon Raman process, we have successfully transferred the magneto-associated Feshbach molecules to the singlet ground state with high efficiency, obtaining up to 8000 23 Na87 Rb molecules with peak number density over 1011 cm-3 in their absolute ground-state level. With an external electric field, we have induced an effective dipole moment over 1 Debye, making 23 Na87 Rb the most dipolar ultracold particle ever achieved. Contrary to the expectation, we observed a rather fast population loss even for 23 Na87 Rb in the absolute ground state with the bi-molecular exchange reaction energetically forbidden. The origin for the short lifetime and possible ways of mitigating it are currently under investigation. Our achievements pave the way toward investigation of ultracold bosonic molecules with strong dipolar interactions. This work is supported by the Hong Kong RGC CUHK404712 and the ANR/RGC Joint Research Scheme ACUHK403/13.

Pulse length of ultracold electron bunches extracted from a laser cooled gas

PubMed Central

Franssen, J. G. H.; Frankort, T. L. I.; Vredenbregt, E. J. D.; Luiten, O. J.

2017-01-01

We present measurements of the pulse length of ultracold electron bunches generated by near-threshold two-photon photoionization of a laser-cooled gas. The pulse length has been measured using a resonant 3 GHz deflecting cavity in TM110 mode. We have measured the pulse length in three ionization regimes. The first is direct two-photon photoionization using only a 480 nm femtosecond laser pulse, which results in short (∼15 ps) but hot (∼104 K) electron bunches. The second regime is just-above-threshold femtosecond photoionization employing the combination of a continuous-wave 780 nm excitation laser and a tunable 480 nm femtosecond ionization laser which results in both ultracold (∼10 K) and ultrafast (∼25 ps) electron bunches. These pulses typically contain ∼103 electrons and have a root-mean-square normalized transverse beam emittance of 1.5 ± 0.1 nm rad. The measured pulse lengths are limited by the energy spread associated with the longitudinal size of the ionization volume, as expected. The third regime is just-below-threshold ionization which produces Rydberg states which slowly ionize on microsecond time scales. PMID:28396879

Effective interactions in a quantum Bose-Bose mixture

NASA Astrophysics Data System (ADS)

Utesov, O. I.; Baglay, M. I.; Andreev, S. V.

2018-05-01

We generalize the Beliaev diagrammatic theory of an interacting spinless Bose-Einstein condensate to the case of a binary mixture. We derive a set of coupled Dyson equations and find analytically the Green's functions of the system. The elementary excitation spectrum consists of two branches, one of which takes the characteristic parabolic form ω ∝p2 in the limit of a spin-independent interaction. We observe renormalization of the magnon mass and the spin-wave velocity due to the Andreev-Bashkin entrainment effect. For a three-dimensional weakly interacting gas the spectrum can be obtained by applying the Bogoliubov transformation to a second-quantized Hamiltonian in which the microscopic two-body potentials in each channel are replaced by the corresponding off-shell scattering amplitudes. The superfluid drag density can be calculated by considering a mixture of phonons and magnons interacting via the effective potentials. We show that this problem is identical to the second-order perturbative treatment of a Bose polaron. In two dimensions the drag contributes to the magnon dispersion already in the first approximation. Our consideration provides a basis for systematic study of emergent phases in quantum degenerate Bose-Bose mixtures.

78 FR 11866 - Sunshine Act Meetings

Federal Register 2010, 2011, 2012, 2013, 2014

2013-02-20

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Spatially distributed multipartite entanglement enables EPR steering of atomic clouds.

PubMed

Kunkel, Philipp; Prüfer, Maximilian; Strobel, Helmut; Linnemann, Daniel; Frölian, Anika; Gasenzer, Thomas; Gärttner, Martin; Oberthaler, Markus K

2018-04-27

A key resource for distributed quantum-enhanced protocols is entanglement between spatially separated modes. However, the robust generation and detection of entanglement between spatially separated regions of an ultracold atomic system remain a challenge. We used spin mixing in a tightly confined Bose-Einstein condensate to generate an entangled state of indistinguishable particles in a single spatial mode. We show experimentally that this entanglement can be spatially distributed by self-similar expansion of the atomic cloud. We used spatially resolved spin read-out to reveal a particularly strong form of quantum correlations known as Einstein-Podolsky-Rosen (EPR) steering between distinct parts of the expanded cloud. Based on the strength of EPR steering, we constructed a witness, which confirmed genuine 5-partite entanglement. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Weyl solitons in three-dimensional optical lattices

NASA Astrophysics Data System (ADS)

Shang, Ce; Zheng, Yuanlin; Malomed, Boris A.

2018-04-01

Weyl fermions are massless chiral quasiparticles existing in materials known as Weyl semimetals. Topological surface states, associated with the unusual electronic structure in the Weyl semimetals, have been recently demonstrated in linear systems. Ultracold atomic gases, featuring laser-assisted tunneling in three-dimensional optical lattices, can be used for the emulation of Weyl semimetals, including nonlinear effects induced by the collisional nonlinearity of atomic Bose-Einstein condensates. We demonstrate that this setting gives rise to topological states in the form of Weyl solitons at the surface of the underlying optical lattice. These nonlinear modes, being exceptionally robust, bifurcate from linear states for a given quasimomentum. The Weyl solitons may be used to design an efficient control scheme for topologically protected unidirectional propagation of excitations in light-matter-interaction physics. After the recently introduced Majorana and Dirac solitons, the Weyl solitons proposed in this work constitute the third (and the last) member in this family of topological solitons.

Creation of quantum-degenerate gases of ytterbium in a compact 2D-/3D-magneto-optical trap setup

DOE Office of Scientific and Technical Information (OSTI.GOV)

Doerscher, Soeren; Thobe, Alexander; Hundt, Bastian

2013-04-15

We report on the first experimental setup based on a 2D-/3D-magneto-optical trap (MOT) scheme to create both Bose-Einstein condensates and degenerate Fermi gases of several ytterbium isotopes. Our setup does not require a Zeeman slower and offers the flexibility to simultaneously produce ultracold samples of other atomic species. Furthermore, the extraordinary optical access favors future experiments in optical lattices. A 2D-MOT on the strong {sup 1}S{sub 0}{yields}{sup 1}P{sub 1} transition captures ytterbium directly from a dispenser of atoms and loads a 3D-MOT on the narrow {sup 1}S{sub 0}{yields}{sup 3}P{sub 1} intercombination transition. Subsequently, atoms are transferred to a crossed opticalmore » dipole trap and cooled evaporatively to quantum degeneracy.« less

Second-scale nuclear spin coherence time of ultracold 23Na40K molecules.

PubMed

Park, Jee Woo; Yan, Zoe Z; Loh, Huanqian; Will, Sebastian A; Zwierlein, Martin W

2017-07-28

Coherence, the stability of the relative phase between quantum states, is central to quantum mechanics and its applications. For ultracold dipolar molecules at sub-microkelvin temperatures, internal states with robust coherence are predicted to offer rich prospects for quantum many-body physics and quantum information processing. We report the observation of stable coherence between nuclear spin states of ultracold fermionic sodium-potassium (NaK) molecules in the singlet rovibrational ground state. Ramsey spectroscopy reveals coherence times on the scale of 1 second; this enables high-resolution spectroscopy of the molecular gas. Collisional shifts are shown to be absent down to the 100-millihertz level. This work opens the door to the use of molecules as a versatile quantum memory and for precision measurements on dipolar quantum matter. Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

State-to-state chemistry for three-body recombination in an ultracold rubidium gas.

PubMed

Wolf, Joschka; Deiß, Markus; Krükow, Artjom; Tiemann, Eberhard; Ruzic, Brandon P; Wang, Yujun; D'Incao, José P; Julienne, Paul S; Denschlag, Johannes Hecker

2017-11-17

Experimental investigation of chemical reactions with full quantum state resolution for all reactants and products has been a long-term challenge. Here we prepare an ultracold few-body quantum state of reactants and demonstrate state-to-state chemistry for the recombination of three spin-polarized ultracold rubidium (Rb) atoms to form a weakly bound Rb 2 molecule. The measured product distribution covers about 90% of the final products, and we are able to discriminate between product states with a level splitting as small as 20 megahertz multiplied by Planck's constant. Furthermore, we formulate propensity rules for the distribution of products, and we develop a theoretical model that predicts many of our experimental observations. The scheme can readily be adapted to other species and opens a door to detailed investigations of inelastic or reactive processes. Copyright © 2017, American Association for the Advancement of Science.

Scattering of a vortex pair by a single quantum vortex in a Bose–Einstein condensate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smirnov, L. A., E-mail: smirnov-lev@allp.sci-nnov.ru; Smirnov, A. I., E-mail: smirnov@appl.sci-nnov.ru; Mironov, V. A.

We analyze the scattering of vortex pairs (the particular case of 2D dark solitons) by a single quantum vortex in a Bose–Einstein condensate with repulsive interaction between atoms. For this purpose, an asymptotic theory describing the dynamics of such 2D soliton-like formations in an arbitrary smoothly nonuniform flow of a ultracold Bose gas is developed. Disregarding the radiation loss associated with acoustic wave emission, we demonstrate that vortex–antivortex pairs can be put in correspondence with quasiparticles, and their behavior can be described by canonical Hamilton equations. For these equations, we determine the integrals of motion that can be used tomore » classify various regimes of scattering of vortex pairs by a single quantum vortex. Theoretical constructions are confirmed by numerical calculations performed directly in terms of the Gross–Pitaevskii equation. We propose a method for estimating the radiation loss in a collision of a soliton-like formation with a phase singularity. It is shown by direct numerical simulation that under certain conditions, the interaction of vortex pairs with a core of a single quantum vortex is accompanied by quite intense acoustic wave emission; as a result, the conditions for applicability of the asymptotic theory developed here are violated. In particular, it is visually demonstrated by a specific example how radiation losses lead to a transformation of a vortex–antivortex pair into a vortex-free 2D dark soliton (i.e., to the annihilation of phase singularities).« less

Relaxation dynamics of a driven two-level system coupled to a Bose-Einstein condensate: application to quantum dot-dipolar exciton gas hybrid systems.

PubMed

Kovalev, Vadim M; Tse, Wang-Kong

2017-11-22

We develop a microscopic theory for the relaxation dynamics of an optically pumped two-level system (TLS) coupled to a bath of weakly interacting Bose gas. Using Keldysh formalism and diagrammatic perturbation theory, expressions for the relaxation times of the TLS Rabi oscillations are derived when the boson bath is in the normal state and the Bose-Einstein condensate (BEC) state. We apply our general theory to consider an irradiated quantum dot coupled with a boson bath consisting of a two-dimensional dipolar exciton gas. When the bath is in the BEC regime, relaxation of the Rabi oscillations is due to both condensate and non-condensate fractions of the bath bosons for weak TLS-light coupling and pre dominantly due to the non-condensate fraction for strong TLS-light coupling. Our theory also shows that a phase transition of the bath from the normal to the BEC state strongly influences the relaxation rate of the TLS Rabi oscillations. The TLS relaxation rate is approximately independent of the pump field frequency and monotonically dependent on the field strength when the bath is in the low-temperature regime of the normal phase. Phase transition of the dipolar exciton gas leads to a non-monotonic dependence of the TLS relaxation rate on both the pump field frequency and field strength, providing a characteristic signature for the detection of BEC phase transition of the coupled dipolar exciton gas.

Relevance of Bose-Einstein condensation to the interference of two independent Bose gases

NASA Astrophysics Data System (ADS)

Iazzi, Mauro; Yuasa, Kazuya

2011-03-01

Interference of two independently prepared ideal Bose gases is discussed, on the basis of the idea of measurement-induced interference. It is known that, even if the number of atoms in each gas is individually fixed finite and the symmetry of the system is not broken, an interference pattern is observed on each single snapshot. The key role is played by the Hanbury Brown and Twiss effect, which leads to an oscillating pattern of the cloud of identical atoms. Then, how essential is the Bose-Einstein condensation to the interference? In this work, we describe two ideal Bose gases trapped in two separate three-dimensional harmonic traps at a finite temperature T, using the canonical ensembles (with fixed numbers of atoms). We compute the full statistics of the snapshot profiles of the expanding and overlapping gases released from the traps. We obtain a simple formula valid for finite T, which shows that the average fringe spectrum (average fringe contrast) is given by the purity of each gas. The purity is known to be a good measure of condensation, and the formula clarifies the relevance of the condensation to the interference. The results for T=0, previously known in the literature, can be recovered from our analysis. The fluctuation of the interference spectrum is also studied, and it is shown that the fluctuation is vanishingly small only below the critical temperature Tc, meaning that interference pattern is certainly observed on every snapshot below Tc. The fact that the number of atoms is fixed in the canonical ensemble is crucial to this vanishing fluctuation.

Nuclear-spin-independent short-range three-body physics in ultracold atoms.

PubMed

Gross, Noam; Shotan, Zav; Kokkelmans, Servaas; Khaykovich, Lev

2010-09-03

We investigate three-body recombination loss across a Feshbach resonance in a gas of ultracold 7Li atoms prepared in the absolute ground state and perform a comparison with previously reported results of a different nuclear-spin state [N. Gross, Phys. Rev. Lett. 103, 163202 (2009)]. We extend the previously reported universality in three-body recombination loss across a Feshbach resonance to the absolute ground state. We show that the positions and widths of recombination minima and Efimov resonances are identical for both states which indicates that the short-range physics is nuclear-spin independent.

Quench-induced breathing mode of one-dimensional Bose gases.

PubMed

Fang, Bess; Carleo, Giuseppe; Johnson, Aisling; Bouchoule, Isabelle

2014-07-18

We measure the position- and momentum-space breathing dynamics of trapped one-dimensional Bose gases at finite temperature. The profile in real space reveals sinusoidal width oscillations whose frequency varies continuously through the quasicondensate to ideal Bose gas crossover. A comparison with theoretical models taking temperature into account is provided. In momentum space, we report the first observation of a frequency doubling in the quasicondensate regime, corresponding to a self-reflection mechanism due to the repulsive interactions. Such a mechanism is predicted for a fermionized system, and has not been observed to date. The disappearance of the frequency doubling through the crossover is mapped out experimentally, giving insights into the dynamics of the breathing evolution.

Quench-Induced Breathing Mode of One-Dimensional Bose Gases

NASA Astrophysics Data System (ADS)

Fang, Bess; Carleo, Giuseppe; Johnson, Aisling; Bouchoule, Isabelle

2014-07-01

We measure the position- and momentum-space breathing dynamics of trapped one-dimensional Bose gases at finite temperature. The profile in real space reveals sinusoidal width oscillations whose frequency varies continuously through the quasicondensate to ideal Bose gas crossover. A comparison with theoretical models taking temperature into account is provided. In momentum space, we report the first observation of a frequency doubling in the quasicondensate regime, corresponding to a self-reflection mechanism due to the repulsive interactions. Such a mechanism is predicted for a fermionized system, and has not been observed to date. The disappearance of the frequency doubling through the crossover is mapped out experimentally, giving insights into the dynamics of the breathing evolution.

Sonic analog of gravitational black holes in bose-einstein condensates

PubMed

Garay; Anglin; Cirac; Zoller

2000-11-27

It is shown that, in dilute-gas Bose-Einstein condensates, there exist both dynamically stable and unstable configurations which, in the hydrodynamic limit, exhibit a behavior resembling that of gravitational black holes. The dynamical instabilities involve creation of quasiparticle pairs in positive and negative energy states, as in the well-known suggested mechanism for black-hole evaporation. We propose a scheme to generate a stable sonic black hole in a ring trap.

Exact Local Correlations and Full Counting Statistics for Arbitrary States of the One-Dimensional Interacting Bose Gas

NASA Astrophysics Data System (ADS)

Bastianello, Alvise; Piroli, Lorenzo; Calabrese, Pasquale

2018-05-01

We derive exact analytic expressions for the n -body local correlations in the one-dimensional Bose gas with contact repulsive interactions (Lieb-Liniger model) in the thermodynamic limit. Our results are valid for arbitrary states of the model, including ground and thermal states, stationary states after a quantum quench, and nonequilibrium steady states arising in transport settings. Calculations for these states are explicitly presented and physical consequences are critically discussed. We also show that the n -body local correlations are directly related to the full counting statistics for the particle-number fluctuations in a short interval, for which we provide an explicit analytic result.

Momentum-Resolved Observation of Thermal and Quantum Depletion in a Bose Gas

NASA Astrophysics Data System (ADS)

Chang, R.; Bouton, Q.; Cayla, H.; Qu, C.; Aspect, A.; Westbrook, C. I.; Clément, D.

2016-12-01

We report on the single-atom-resolved measurement of the distribution of momenta ℏk in a weakly interacting Bose gas after a 330 ms time of flight. We investigate it for various temperatures and clearly separate two contributions to the depletion of the condensate by their k dependence. The first one is the thermal depletion. The second contribution falls off as k-4, and its magnitude increases with the in-trap condensate density as predicted by the Bogoliubov theory at zero temperature. These observations suggest associating it with the quantum depletion. How this contribution can survive the expansion of the released interacting condensate is an intriguing open question.

Angular Momentum of a Bose-Einstein Condensate in a Synthetic Rotational Field

NASA Astrophysics Data System (ADS)

Qu, Chunlei; Stringari, Sandro

2018-05-01

By applying a position-dependent detuning to a spin-orbit-coupled Hamiltonian with equal Rashba and Dresselhaus coupling, we exploit the behavior of the angular momentum of a harmonically trapped Bose-Einstein condensed atomic gas and discuss the distinctive role of its canonical and spin components. By developing the formalism of spinor hydrodynamics, we predict the precession of the dipole oscillation caused by the synthetic rotational field, in analogy with the precession of the Foucault pendulum, the excitation of the scissors mode, following the sudden switching off of the detuning, and the occurrence of Hall-like effects. When the detuning exceeds a critical value, we observe a transition from a vortex free, rigidly rotating quantum gas to a gas containing vortices with negative circulation which results in a significant reduction of the total angular momentum.

Monte Carlo wave-function description of losses in a one-dimensional Bose gas and cooling to the ground state by quantum feedback

NASA Astrophysics Data System (ADS)

Schemmer, M.; Johnson, A.; Photopoulos, R.; Bouchoule, I.

2017-04-01

The effect of atom losses on a homogeneous one-dimensional Bose gas lying within the quasicondensate regime is investigated using a Monte Carlo wave-function approach. The evolution of the system is calculated, conditioned by the loss sequence, namely, the times of individual losses and the position of the removed atoms. We describe the gas within the linearized Bogoliubov approach. For each mode, we find that, for a given quantum trajectory, the state of the system converges towards a coherent state, i.e., the ground state, displaced in phase space. We show that, provided losses are recorded with a temporal and spatially resolved detector, quantum feedback can be implemented and cooling to the ground state of one or several modes can be realized.

Critical behavior of the ideal-gas Bose-Einstein condensation in the Apollonian network.

PubMed

de Oliveira, I N; dos Santos, T B; de Moura, F A B F; Lyra, M L; Serva, M

2013-08-01

We show that the ideal Boson gas displays a finite-temperature Bose-Einstein condensation transition in the complex Apollonian network exhibiting scale-free, small-world, and hierarchical properties. The single-particle tight-binding Hamiltonian with properly rescaled hopping amplitudes has a fractal-like energy spectrum. The energy spectrum is analytically demonstrated to be generated by a nonlinear mapping transformation. A finite-size scaling analysis over several orders of magnitudes of network sizes is shown to provide precise estimates for the exponents characterizing the condensed fraction, correlation size, and specific heat. The critical exponents, as well as the power-law behavior of the density of states at the bottom of the band, are similar to those of the ideal Boson gas in lattices with spectral dimension d(s)=2ln(3)/ln(9/5)~/=3.74.

Precursor of superfluidity in a strongly interacting Fermi gas with negative effective range

NASA Astrophysics Data System (ADS)

Tajima, Hiroyuki

2018-04-01

We investigate theoretically the effects of pairing fluctuations in an ultracold Fermi gas near a Feshbach resonance with a negative effective range. By employing a many-body T -matrix theory with a coupled fermion-boson model, we show that the single-particle density of states exhibits the so-called pseudogap phenomenon, which is a precursor of superfluidity induced by strong pairing fluctuations. We clarify the region where strong pairing fluctuations play a crucial role in single-particle properties, from the broad-resonance region to the narrow-resonance limit at the divergent two-body scattering length. We also extrapolate the effects of pairing fluctuations to the positive-effective-range region from our results near the narrow Feshbach resonance. Results shown in this paper are relevant to the connection between ultracold Fermi gases and low-density neutron matter from the viewpoint of finite-effective-range corrections.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cai Xiaoming; Chen Shu; Wang Yupeng

The superfluid-to-Anderson-insulator transition of a strongly repulsive Bose gas is studied in a one-dimensional incommensurate optical lattice. In the hard-core limit, the Bose-Fermi mapping allows us to deal with the system using the exact numerical method. Based on the Aubry-Andre model, we exploit the phase transition of the hard-core boson system from the superfluid phase with all single-particle states extended to the Bose-glass phase with all the single-particle states being Anderson localized as the strength of the incommensurate potential increases relative to the hopping amplitude. We evaluate the superfluid fraction, one-particle density matrices, momentum distributions, the natural orbitals, and theirmore » occupations. All of these quantities show that there exists a superfluid-to-insulator phase transition in the system.« less

First and second sound in a two-dimensional harmonically trapped Bose gas across the Berezinskii–Kosterlitz–Thouless transition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Xia-Ji, E-mail: xiajiliu@swin.edu.au; Hu, Hui, E-mail: hhu@swin.edu.au

2014-12-15

We theoretically investigate first and second sound of a two-dimensional (2D) atomic Bose gas in harmonic traps by solving Landau’s two-fluid hydrodynamic equations. For an isotropic trap, we find that first and second sound modes become degenerate at certain temperatures and exhibit typical avoided crossings in mode frequencies. At these temperatures, second sound has significant density fluctuation due to its hybridization with first sound and has a divergent mode frequency towards the Berezinskii–Kosterlitz–Thouless (BKT) transition. For a highly anisotropic trap, we derive the simplified one-dimensional hydrodynamic equations and discuss the sound-wave propagation along the weakly confined direction. Due to themore » universal jump of the superfluid density inherent to the BKT transition, we show that the first sound velocity exhibits a kink across the transition. These predictions might be readily examined in current experimental setups for 2D dilute Bose gases with a sufficiently large number of atoms, where the finite-size effect due to harmonic traps is relatively weak.« less

Condensate statistics and thermodynamics of weakly interacting Bose gas: Recursion relation approach

NASA Astrophysics Data System (ADS)

Dorfman, K. E.; Kim, M.; Svidzinsky, A. A.

2011-03-01

We study condensate statistics and thermodynamics of weakly interacting Bose gas with a fixed total number N of particles in a cubic box. We find the exact recursion relation for the canonical ensemble partition function. Using this relation, we calculate the distribution function of condensate particles for N=200. We also calculate the distribution function based on multinomial expansion of the characteristic function. Similar to the ideal gas, both approaches give exact statistical moments for all temperatures in the framework of Bogoliubov model. We compare them with the results of unconstraint canonical ensemble quasiparticle formalism and the hybrid master equation approach. The present recursion relation can be used for any external potential and boundary conditions. We investigate the temperature dependence of the first few statistical moments of condensate fluctuations as well as thermodynamic potentials and heat capacity analytically and numerically in the whole temperature range.

Rayleigh surface wave interaction with the 2D exciton Bose-Einstein condensate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boev, M. V.; Kovalev, V. M., E-mail: vadimkovalev@isp.nsc.ru

We describe the interaction of a Rayleigh surface acoustic wave (SAW) traveling on the semiconductor substrate with the excitonic gas in a double quantum well located on the substrate surface. We study the SAW attenuation and its velocity renormalization due to the coupling to excitons. Both the deformation potential and piezoelectric mechanisms of the SAW-exciton interaction are considered. We focus on the frequency and excitonic density dependences of the SAW absorption coefficient and velocity renormalization at temperatures both above and well below the critical temperature of Bose-Einstein condensation of the excitonic gas. We demonstrate that the SAW attenuation and velocitymore » renormalization are strongly different below and above the critical temperature.« less

Slow quench dynamics of a one-dimensional Bose gas confined to an optical lattice.

PubMed

Bernier, Jean-Sébastien; Roux, Guillaume; Kollath, Corinna

2011-05-20

We analyze the effect of a linear time variation of the interaction strength on a trapped one-dimensional Bose gas confined to an optical lattice. The evolution of different observables such as the experimentally accessible on site particle distribution are studied as a function of the ramp time by using time-dependent numerical techniques. We find that the dynamics of a trapped system typically displays two regimes: For long ramp times, the dynamics is governed by density redistribution, while at short ramp times, local dynamics dominates as the evolution is identical to that of an homogeneous system. In the homogeneous limit, we also discuss the nontrivial scaling of the energy absorbed with the ramp time.

Many-body physics using cold atoms

NASA Astrophysics Data System (ADS)

Sundar, Bhuvanesh

Advances in experiments on dilute ultracold atomic gases have given us access to highly tunable quantum systems. In particular, there have been substantial improvements in achieving different kinds of interaction between atoms. As a result, utracold atomic gases oer an ideal platform to simulate many-body phenomena in condensed matter physics, and engineer other novel phenomena that are a result of the exotic interactions produced between atoms. In this dissertation, I present a series of studies that explore the physics of dilute ultracold atomic gases in different settings. In each setting, I explore a different form of the inter-particle interaction. Motivated by experiments which induce artificial spin-orbit coupling for cold fermions, I explore this system in my first project. In this project, I propose a method to perform universal quantum computation using the excitations of interacting spin-orbit coupled fermions, in which effective p-wave interactions lead to the formation of a topological superfluid. Motivated by experiments which explore the physics of exotic interactions between atoms trapped inside optical cavities, I explore this system in a second project. I calculate the phase diagram of lattice bosons trapped in an optical cavity, where the cavity modes mediates effective global range checkerboard interactions between the atoms. I compare this phase diagram with one that was recently measured experimentally. In two other projects, I explore quantum simulation of condensed matter phenomena due to spin-dependent interactions between particles. I propose a method to produce tunable spin-dependent interactions between atoms, using an optical Feshbach resonance. In one project, I use these spin-dependent interactions in an ultracold Bose-Fermi system, and propose a method to produce the Kondo model. I propose an experiment to directly observe the Kondo effect in this system. In another project, I propose using lattice bosons with a large hyperfine spin, which have Feshbach-induced spin-dependent interactions, to produce a quantum dimer model. I propose an experiment to detect the ground state in this system. In a final project, I develop tools to simulate the dynamics of fermionic superfluids in which fermions interact via a short-range interaction.

78 FR 19700 - Columbia Gas Transmission, LLC; Notice of Request Under Blanket Authorization

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2013-04-02

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Quantum entanglement of identical particles by standard information-theoretic notions

PubMed Central

Lo Franco, Rosario; Compagno, Giuseppe

2016-01-01

Quantum entanglement of identical particles is essential in quantum information theory. Yet, its correct determination remains an open issue hindering the general understanding and exploitation of many-particle systems. Operator-based methods have been developed that attempt to overcome the issue. Here we introduce a state-based method which, as second quantization, does not label identical particles and presents conceptual and technical advances compared to the previous ones. It establishes the quantitative role played by arbitrary wave function overlaps, local measurements and particle nature (bosons or fermions) in assessing entanglement by notions commonly used in quantum information theory for distinguishable particles, like partial trace. Our approach furthermore shows that bringing identical particles into the same spatial location functions as an entangling gate, providing fundamental theoretical support to recent experimental observations with ultracold atoms. These results pave the way to set and interpret experiments for utilizing quantum correlations in realistic scenarios where overlap of particles can count, as in Bose-Einstein condensates, quantum dots and biological molecular aggregates. PMID:26857475

Anisotropic quantum quench in the presence of frustration or background gauge fields: A probe of bulk currents and topological chiral edge modes

NASA Astrophysics Data System (ADS)

Killi, Matthew; Trotzky, Stefan; Paramekanti, Arun

2012-12-01

Bosons and fermions, in the presence of frustration or background gauge fields, can form many-body ground states that support equilibrium charge or spin currents. Motivated by the experimental creation of frustration or synthetic gauge fields in ultracold atomic systems, we propose a general scheme by which making a sudden anisotropic quench of the atom tunneling across the lattice and tracking the ensuing density modulations provides a powerful and gauge-invariant route to probing diverse equilibrium current patterns. Using illustrative examples of trapped superfluid Bose and normal Fermi systems in the presence of artificial magnetic fluxes on square lattices, and frustrated bosons in a triangular lattice, we show that this scheme to probe equilibrium bulk current order works independent of particle statistics. We also show that such quenches can detect chiral edge modes in gapped topological states, such as quantum Hall or quantum spin Hall insulators.

Superconductor-insulator transition and Fermi-Bose crossovers

DOE PAGES

Loh, Yen Lee; Randeria, Mohit; Trivedi, Nandini; ...

2016-05-31

The direct transition from an insulator to a superconductor (SC) in Fermi systems is a problem of long-standing interest, which necessarily goes beyond the standard BCS paradigm of superconductivity as a Fermi surface instability. We introduce here a simple, translationally invariant lattice fermion model that undergoes a SC-insulator transition (SIT) and elucidate its properties using analytical methods and quantum Monte Carlo simulations. We show that there is a fermionic band insulator to bosonic insulator crossover in the insulating phase and a BCS-to-BEC crossover in the SC. The SIT is always found to be from a bosonic insulator to a BEC-likemore » SC, with an energy gap for fermions that remains finite across the SIT. Hence, the energy scales that go critical at the SIT are the gap to pair excitations in the insulator and the superfluid stiffness in the SC. In addition to giving insight into important questions about the SIT in solid-state systems, our model should be experimentally realizable using ultracold fermions in optical lattices.« less

Quantum many-body dynamics of dark solitons in optical lattices

NASA Astrophysics Data System (ADS)

Mishmash, R. V.; Danshita, I.; Clark, Charles W.; Carr, L. D.

2009-11-01

We present a fully quantum many-body treatment of dark solitons formed by ultracold bosonic atoms in one-dimensional optical lattices. Using time-evolving block decimation to simulate the single-band Bose-Hubbard Hamiltonian, we consider the quantum dynamics of density and phase engineered dark solitons as well as the quantum evolution of mean-field dark solitons injected into the quantum model. The former approach directly models how one may create quantum entangled dark solitons in experiment. While we have already presented results regarding the latter approach elsewhere [R. V. Mishmash and L. D. Carr, Phys. Rev. Lett. 103, 140403 (2009)], we expand upon those results in this work. In both cases, quantum fluctuations cause the dark soliton to fill in and may induce an inelasticity in soliton-soliton collisions. Comparisons are made to the Bogoliubov theory which predicts depletion into an anomalous mode that fills in the soliton. Our many-body treatment allows us to go beyond the Bogoliubov approximation and calculate explicitly the dynamics of the system’s natural orbitals.

Superconductivity in an electron band just above the Fermi level: possible route to BCS-BEC superconductivity.

PubMed

Okazaki, K; Ito, Y; Ota, Y; Kotani, Y; Shimojima, T; Kiss, T; Watanabe, S; Chen, C-T; Niitaka, S; Hanaguri, T; Takagi, H; Chainani, A; Shin, S

2014-02-28

Conventional superconductivity follows Bardeen-Cooper-Schrieffer(BCS) theory of electrons-pairing in momentum-space, while superfluidity is the Bose-Einstein condensation(BEC) of atoms paired in real-space. These properties of solid metals and ultra-cold gases, respectively, are connected by the BCS-BEC crossover. Here we investigate the band dispersions in FeTe(0.6)Se(0.4)(Tc = 14.5 K ~ 1.2 meV) in an accessible range below and above the Fermi level(EF) using ultra-high resolution laser angle-resolved photoemission spectroscopy. We uncover an electron band lying just 0.7 meV (~8 K) above EF at the Γ-point, which shows a sharp superconducting coherence peak with gap formation below Tc. The estimated superconducting gap Δ and Fermi energy [Symbol: see text]F indicate composite superconductivity in an iron-based superconductor, consisting of strong-coupling BEC in the electron band and weak-coupling BCS-like superconductivity in the hole band. The study identifies the possible route to BCS-BEC superconductivity.

Ordered structures in rotating ultracold Bose gases

NASA Astrophysics Data System (ADS)

Barberán, N.; Lewenstein, M.; Osterloh, K.; Dagnino, D.

2006-06-01

Two-dimentional systems of trapped samples of few cold bosonic atoms submitted to strong rotation around the perpendicular axis may be realized in optical lattices and microtraps. We investigate theoretically the evolution of ground state structures of such systems as the rotational frequency Ω increases. Various kinds of ordered structures are observed. In some cases, hidden interference patterns exhibit themselves only in the pair correlation function; in some other cases explicit broken-symmetry structures appear that modulate the density. For N<10 atoms, the standard scenario, valid for large sytems is absent, and is only gradually recovered as N increases. On the one hand, the Laughlin state in the strong rotational regime contains ordered structures much more similar to a Wigner molecule than to a fermionic quantum liquid. On the other hand, in the weak rotational regime, the possibility to obtain equilibrium states, whose density reveals an array of vortices, is restricted to the vicinity of some critical values of the rotational frequency Ω .

Cavity-induced artificial gauge field in a Bose-Hubbard ladder

NASA Astrophysics Data System (ADS)

Halati, Catalin-Mihai; Sheikhan, Ameneh; Kollath, Corinna

2017-12-01

We consider theoretically ultracold interacting bosonic atoms confined to quasi-one-dimensional ladder structures formed by optical lattices and coupled to the field of an optical cavity. The atoms can collect a spatial phase imprint during a cavity-assisted tunneling along a rung via Raman transitions employing a cavity mode and a transverse running wave pump beam. By adiabatic elimination of the cavity field we obtain an effective Hamiltonian for the bosonic atoms, with a self-consistency condition. Using the numerical density-matrix renormalization-group method, we obtain a rich steady-state diagram of self-organized steady states. Transitions between superfluid to Mott-insulating states occur, on top of which we can have Meissner, vortex liquid, and vortex lattice phases. Also a state that explicitly breaks the symmetry between the two legs of the ladder, namely, the biased-ladder phase, is dynamically stabilized. We investigate the influence that a trapping potential has on the stability of the self-organized phases.

Focus on strongly correlated quantum fluids: from ultracold quantum gases to QCD plasmas Focus on strongly correlated quantum fluids: from ultracold quantum gases to QCD plasmas

NASA Astrophysics Data System (ADS)

Adams, Allan; Carr, Lincoln D.; Schaefer, Thomas; Steinberg, Peter; Thomas, John E.

2013-04-01

The last few years have witnessed a dramatic convergence of three distinct lines of research concerned with different kinds of extreme quantum matter. Two of these involve new quantum fluids that can be studied in the laboratory, ultracold quantum gases and quantum chromodynamics (QCD) plasmas. Even though these systems involve vastly different energy scales, the physical properties of the two quantum fluids are remarkably similar. The third line of research is based on the discovery of a new theoretical tool for investigating the properties of extreme quantum matter, holographic dualties. The main goal of this focus issue is to foster communication and understanding between these three fields. We proceed to describe each in more detail. Ultracold quantum gases offer a new paradigm for the study of nonperturbative quantum many-body physics. With widely tunable interaction strength, spin composition, and temperature, using different hyperfine states one can model spin-1/2 fermions, spin-3/2 fermions, and many other spin structures of bosons, fermions, and mixtures thereof. Such systems have produced a revolution in the study of strongly interacting Fermi systems, for example in the Bardeen-Cooper-Schrieffer (BCS) to Bose-Einstein condensate (BEC) crossover region, where a close collaboration between experimentalists and theorists—typical in this field—enabled ground-breaking studies in an area spanning several decades. Half-way through this crossover, when the scattering length characterizing low-energy collisions diverges, one obtains a unitary quantum gas, which is universal and scale invariant. The unitary gas has close parallels in the hydrodynamics of QCD plasmas, where the ratio of viscosity to entropy density is extremely low and comparable to the minimum viscosity conjecture, an important prediction of AdS/CFT (see below). Exciting developments in the thermodynamic and transport properties of strongly interacting Fermi gases are of broad interdisciplinary appeal and include new studies of high temperature superfluidity, viscosity, spin-transport, spin-imbalanced mixtures, and three-component gases, this last having a close parallel to color superconductivity. Another system important for the field of strongly-interacting quantum fluids was revealed by analysis of data from the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. Despite naive expectations based on asymptotic freedom that the deconfinement of quarks and gluons at high temperatures would lead to a weakly-interacting quark gluon plasma (QGP), the system appeared to be quite strongly coupled. Subsequent estimates of the viscosity-to-entropy ratio suggest that the system is tantalizingly close to the postulated bound from AdS/CFT calculations. The field is quite dynamic at the moment; new measurements are expected from upgraded detectors at RHIC, and an entirely new energy regime is being opened up by heavy ion collisions at the Large Hadron Collider (LHC) at CERN. On the theoretical side, much work remains to be done to extract the precise values of the transport coefficients, and to characterize the nature of quasi-particle excitations in the plasma. Finally, holographic dualities such as anti-de Sitter/conformal field theory (AdS/CFT) have opened a new theoretical window on strongly correlated fluids. Holography relates strongly-interacting quantum many-body systems to weakly-coupled semi-classical gravitational systems, replacing quasiparticles with geometry and translating various difficult questions about quantum fluids into simple and calculable geometric exercises. Already, some of the earliest lessons of holography, such as the conjectural bound on the viscosity-to-entropy ratio, have had a considerable impact on the theoretical and experimental study of strongly correlated fluids, from RHIC to ultracold atoms. More recently, the study of holographic superconductors, non-Fermi liquids and unitary quantum gases has touched off a flurry of interest in holography as a toolkit for studying strongly-correlated many-body systems more generally. Holography also allows us to use results from quantum fluids to study classical and quantum gravity; for example, the phase structure of a quantum many-body system translates into a rich classification of black holes in the dual space-time. Given both the rapid progress in applied holography and the exciting developments in ultracold quantum gases and QCD plasmas discussed above, the time is ripe for new collaborations across traditional lines of specialization. This focus issue explores the convergence between three heretofore separate areas of physics. Over forty research groups have contributed original work, and there will be a review article which complements these advances, overviewing them and presenting them in the context of all three fields and their interconnections. The review concludes with a list of open questions. This sets the tone for the present focus issue; namely, interdisciplinary dialog, openness, innovation, and possibility, an emphasis for which New Journal of Physics, an open-access journal of the highest quality, is especially fitted.

Single-shot imaging of trapped Fermi gas

NASA Astrophysics Data System (ADS)

Gajda, Mariusz; Mostowski, Jan; Sowiński, Tomasz; Załuska-Kotur, Magdalena

2016-07-01

Recently developed techniques allow for simultaneous measurements of the positions of all ultra-cold atoms in a trap with high resolution. Each such single-shot experiment detects one element of the quantum ensemble formed by the cloud of atoms. Repeated single-shot measurements can be used to determine all correlations between particle positions as opposed to standard measurements that determine particle density or two-particle correlations only. In this paper we discuss the possible outcomes of such single-shot measurements in the case of cloud of ultra-cold noninteracting Fermi atoms. We show that the Pauli exclusion principle alone leads to correlations between particle positions that originate from unexpected spatial structures formed by the atoms.

Strongly interacting high-partial-wave Bose gas

NASA Astrophysics Data System (ADS)

Yao, Juan; Qi, Ran; Zhang, Pengfei

2018-04-01

Motivated by recent experimental progress, we make an investigation of p - and d -wave resonant Bose gas. An explanation of the Nozières and Schmitt-Rink (NSR) scheme in terms of two-channel model is provided. Different from the s -wave case, high-partial-wave interaction supports a quasibound state in the weak-coupling regime. Within the NSR approximation, we study the equation of state, critical temperature, and particle population distributions. We clarify the effect of the quasibound state on the phase diagram and the dimer production. A multicritical point where normal phase, atomic superfluid phase, and molecular superfluid phase meet is predicted within the phase diagram. We also show the occurrence of a resonant conversion between solitary atoms and dimers when temperature kBT approximates the quasibound energy.

Polaron in the dilute critical Bose condensate

NASA Astrophysics Data System (ADS)

Pastukhov, Volodymyr

2018-05-01

The properties of an impurity immersed in a dilute D-dimensional Bose gas at temperatures close to its second-order phase transition point are considered. Particularly by means of the 1/N-expansion, we calculate the leading-order polaron energy and the damping rate in the limit of vanishing boson–boson interaction. It is shown that the perturbative effective mass and the quasiparticle residue diverge logarithmically in the long-length limit, signalling the non-analytic behavior of the impurity spectrum and pole-free structure of the polaron Green’s function in the infrared region, respectively.

Direct observation of ultrafast many-body electron dynamics in an ultracold Rydberg gas

PubMed Central

Takei, Nobuyuki; Sommer, Christian; Genes, Claudiu; Pupillo, Guido; Goto, Haruka; Koyasu, Kuniaki; Chiba, Hisashi; Weidemüller, Matthias; Ohmori, Kenji

2016-01-01

Many-body correlations govern a variety of important quantum phenomena such as the emergence of superconductivity and magnetism. Understanding quantum many-body systems is thus one of the central goals of modern sciences. Here we demonstrate an experimental approach towards this goal by utilizing an ultracold Rydberg gas generated with a broadband picosecond laser pulse. We follow the ultrafast evolution of its electronic coherence by time-domain Ramsey interferometry with attosecond precision. The observed electronic coherence shows an ultrafast oscillation with a period of 1 femtosecond, whose phase shift on the attosecond timescale is consistent with many-body correlations among Rydberg atoms beyond mean-field approximations. This coherent and ultrafast many-body dynamics is actively controlled by tuning the orbital size and population of the Rydberg state, as well as the mean atomic distance. Our approach will offer a versatile platform to observe and manipulate non-equilibrium dynamics of quantum many-body systems on the ultrafast timescale. PMID:27849054

Bose-Einstein Condensation of Long-Lifetime Polaritons in Thermal Equilibrium.

PubMed

Sun, Yongbao; Wen, Patrick; Yoon, Yoseob; Liu, Gangqiang; Steger, Mark; Pfeiffer, Loren N; West, Ken; Snoke, David W; Nelson, Keith A

2017-01-06

The experimental realization of Bose-Einstein condensation (BEC) with atoms and quasiparticles has triggered wide exploration of macroscopic quantum effects. Microcavity polaritons are of particular interest because quantum phenomena such as BEC and superfluidity can be observed at elevated temperatures. However, polariton lifetimes are typically too short to permit thermal equilibration. This has led to debate about whether polariton condensation is intrinsically a nonequilibrium effect. Here we report the first unambiguous observation of BEC of optically trapped polaritons in thermal equilibrium in a high-Q microcavity, evidenced by equilibrium Bose-Einstein distributions over broad ranges of polariton densities and bath temperatures. With thermal equilibrium established, we verify that polariton condensation is a phase transition with a well-defined density-temperature phase diagram. The measured phase boundary agrees well with the predictions of basic quantum gas theory.

Quasiparticle Properties of a Mobile Impurity in a Bose-Einstein Condensate.

PubMed

Christensen, Rasmus Søgaard; Levinsen, Jesper; Bruun, Georg M

2015-10-16

We develop a systematic perturbation theory for the quasiparticle properties of a single impurity immersed in a Bose-Einstein condensate. Analytical results are derived for the impurity energy, effective mass, and residue to third order in the impurity-boson scattering length. The energy is shown to depend logarithmically on the scattering length to third order, whereas the residue and the effective mass are given by analytical power series. When the boson-boson scattering length equals the boson-impurity scattering length, the energy has the same structure as that of a weakly interacting Bose gas, including terms of the Lee-Huang-Yang and fourth order logarithmic form. Our results, which cannot be obtained within the canonical Fröhlich model of an impurity interacting with phonons, provide valuable benchmarks for many-body theories and for experiments.

Ultra-cold molecules in an atomic Bose-Einstein condensate

NASA Astrophysics Data System (ADS)

Wynar, Roahn Helden

2000-08-01

This thesis is about photoassociation of Bose-condensed 87Rb. Most importantly we report that state selected 87Rb2 molecules were created at rest in a condensate of 87Rb using two-photon photoassociation. Additionally, we have identified three weakly bound states of the 87Rb2 S+u3 , potential for the |1, -1> + |1, - 1> collisional channel. The binding energies of these states are 529.4 +/- .07, 636.0094 +/- .0012, and 24.24 +/- .01 MHz respectively. We have also carried out a detailed study of the density dependence of the shift and width of the two-photon lineshape. This shift and width is modeled using the theory of Bohn and Julienne [34] and in addition to the precise measurement of binding energy we also report the first measurement of an atom molecule scattering length, aam, which we conclude is -180 +/- 150 a0, and the inelastic collision rate, Kinel < 8 × 10-11 cm-3/s. Stimulated Raman free bound coupling in an atomic Bose- Einstein condensate may lead to the formation of a molecular condensate. In order to evaluate this possibility we present a many-body quantum mean field theory of a Bose-Einstein condensate that includes a density dependent coherent coupling between atoms and molecules. This theory yields two coupled equations, one for the evolution of atomic condensate amplitude and one for the evolution of molecular condensate amplitude. The nature of the atomic-molecular condensate evolution is shown to depend on six, model parameters including the coherent coupling, given by cn . The other five parameters can be interpreted as light-shifts and incoherent loss rates. We present a calculation intended to estimate the values of these six parameters for the 87Rb - 87Rb 2 system. Based on the results of this calculation we identify two locations in the 87Rb2 spectrum where coherent transfer of population from atomic condensate to molecular condensate is plausible. Finally, we examine the credibility of the theoretical model used to estimate the six parameters used by the mean field theory. By comparing the measured Stark shifts of two-color resonances with predictions based on our theoretical model we conclude that the model is satisfactory for the v = 37 level of the S+u3 potential. This work also describes the experimental details of stabilizing a Coherent 899-01 Ti:Saphire laser and the experimental methods important to executing photoassociation in a time-averaged-orbiting potential (TOP) trap.

Microwave ac Zeeman force for ultracold atoms

NASA Astrophysics Data System (ADS)

Fancher, C. T.; Pyle, A. J.; Rotunno, A. P.; Aubin, S.

2018-04-01

We measure the ac Zeeman force on an ultracold gas of 87Rb due to a microwave magnetic field targeted to the 6.8 GHz hyperfine splitting of these atoms. An atom chip produces a microwave near field with a strong amplitude gradient, and we observe a force over three times the strength of gravity. Our measurements are consistent with a simple two-level theory for the ac Zeeman effect and demonstrate its resonant, bipolar, and spin-dependent nature. We observe that the dressed-atom eigenstates gradually mix over time and have mapped out this behavior as a function of magnetic field and detuning. We demonstrate the practical spin selectivity of the force by pushing or pulling a specific spin state while leaving other spin states unmoved.

An approach to spin-resolved molecular gas microscopy

NASA Astrophysics Data System (ADS)

Covey, Jacob P.; De Marco, Luigi; Acevedo, Óscar L.; Rey, Ana Maria; Ye, Jun

2018-04-01

Ultracold polar molecules are an ideal platform for studying many-body physics with long-range dipolar interactions. Experiments in this field have progressed enormously, and several groups are pursuing advanced apparatus for manipulation of molecules with electric fields as well as single-atom-resolved in situ detection. Such detection has become ubiquitous for atoms in optical lattices and tweezer arrays, but has yet to be demonstrated for ultracold polar molecules. Here we present a proposal for the implementation of site-resolved microscopy for polar molecules, and specifically discuss a technique for spin-resolved molecular detection. We use numerical simulation of spin dynamics of lattice-confined polar molecules to show how such a scheme would be of utility in a spin-diffusion experiment.

75 FR 62519 - Rocky Mountain Natural Gas LLC; KeySpan Gas East Corporation; ECOP Gas Company, LLC; MGTC, Inc...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-10-12

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. PR10-130-000; PR10-131-000; PR10-132-000; PR10-133-000; PR10-134-000; PR10-135-000; PR10-136-000 (Not Consolidated)] Rocky Mountain.... Bose, Secretary. [FR Doc. 2010-25519 Filed 10-8-10; 8:45 am] BILLING CODE 6717-01-P ...

Inflationary Quasiparticle Creation and Thermalization Dynamics in Coupled Bose-Einstein Condensates

NASA Astrophysics Data System (ADS)

Posazhennikova, Anna; Trujillo-Martinez, Mauricio; Kroha, Johann

2016-06-01

A Bose gas in a double-well potential, exhibiting a true Bose-Einstein condensate (BEC) amplitude and initially performing Josephson oscillations, is a prototype of an isolated, nonequilibrium many-body system. We investigate the quasiparticle (QP) creation and thermalization dynamics of this system by solving the time-dependent Keldysh-Bogoliubov equations. We find avalanchelike QP creation due to a parametric resonance between BEC and QP oscillations, followed by slow, exponential relaxation to a thermal state at an elevated temperature, controlled by the initial excitation energy of the oscillating BEC above its ground state. The crossover between the two regimes occurs because of an effective decoupling of the QP and BEC oscillations. This dynamics is analogous to elementary particle creation in models of the early universe. The thermalization in our setup occurs because the BEC acts as a grand canonical reservoir for the quasiparticle system.

Thermally activated phase slips of one-dimensional Bose gases in shallow optical lattices

NASA Astrophysics Data System (ADS)

Kunimi, Masaya; Danshita, Ippei

2017-03-01

We study the decay of superflow via thermally activated phase slips in one-dimensional Bose gases in a shallow optical lattice. By using the Kramers formula, we numerically calculate the nucleation rate of a thermally activated phase slip for various values of the filling factor and flow velocity in the absence of a harmonic trapping potential. Within the local density approximation, we derive a formula connecting the phase-slip nucleation rate with the damping rate of a dipole oscillation of the Bose gas in the presence of a harmonic trap. We use the derived formula to directly compare our theory with the recent experiment done by the LENS group [L. Tanzi et al., Sci. Rep. 6, 25965 (2016), 10.1038/srep25965]. From the comparison, the observed damping of dipole oscillations in a weakly correlated and small velocity regime is attributed dominantly to thermally activated phase slips rather than quantum phase slips.

High-Temperature Nonequilibrium Bose Condensation Induced by a Hot Needle.

PubMed

Schnell, Alexander; Vorberg, Daniel; Ketzmerick, Roland; Eckardt, André

2017-10-06

We investigate theoretically a one-dimensional ideal Bose gas that is driven into a steady state far from equilibrium via the coupling to two heat baths: a global bath of temperature T and a "hot needle," a bath of temperature T_{h}≫T with localized coupling to the system. Remarkably, this system features a crossover to finite-size Bose condensation at temperatures T that are orders of magnitude larger than the equilibrium condensation temperature. This counterintuitive effect is explained by a suppression of long-wavelength excitations resulting from the competition between both baths. Moreover, for sufficiently large needle temperatures ground-state condensation is superseded by condensation into an excited state, which is favored by its weaker coupling to the hot needle. Our results suggest a general strategy for the preparation of quantum degenerate nonequilibrium steady states with unconventional properties and at large temperatures.

Optimized evaporative cooling for sodium Bose-Einstein condensation against three-body loss

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shobu, Takahiko; Yamaoka, Hironobu; Imai, Hiromitsu

2011-09-15

We report on a highly efficient evaporative cooling optimized experimentally. We successfully created sodium Bose-Einstein condensates with 6.4x10{sup 7} atoms starting from 6.6x10{sup 9} thermal atoms trapped in a magnetic trap by employing a fast linear sweep of radio frequency at the final stage of evaporative cooling so as to overcome the serious three-body losses. The experimental results such as the cooling trajectory and the condensate growth quantitatively agree with the numerical simulations of evaporative cooling on the basis of the kinetic theory of a Bose gas carefully taking into account our specific experimental conditions. We further discuss theoretically amore » possibility of producing large condensates, more than 10{sup 8} sodium atoms, by simply increasing the number of initial thermal trapped atoms and the corresponding optimization of evaporative cooling.« less

Inflationary Quasiparticle Creation and Thermalization Dynamics in Coupled Bose-Einstein Condensates.

PubMed

Posazhennikova, Anna; Trujillo-Martinez, Mauricio; Kroha, Johann

2016-06-03

A Bose gas in a double-well potential, exhibiting a true Bose-Einstein condensate (BEC) amplitude and initially performing Josephson oscillations, is a prototype of an isolated, nonequilibrium many-body system. We investigate the quasiparticle (QP) creation and thermalization dynamics of this system by solving the time-dependent Keldysh-Bogoliubov equations. We find avalanchelike QP creation due to a parametric resonance between BEC and QP oscillations, followed by slow, exponential relaxation to a thermal state at an elevated temperature, controlled by the initial excitation energy of the oscillating BEC above its ground state. The crossover between the two regimes occurs because of an effective decoupling of the QP and BEC oscillations. This dynamics is analogous to elementary particle creation in models of the early universe. The thermalization in our setup occurs because the BEC acts as a grand canonical reservoir for the quasiparticle system.

Measurement of optical Feshbach resonances in an ideal gas.

PubMed

Blatt, S; Nicholson, T L; Bloom, B J; Williams, J R; Thomsen, J W; Julienne, P S; Ye, J

2011-08-12

Using a narrow intercombination line in alkaline earth atoms to mitigate large inelastic losses, we explore the optical Feshbach resonance effect in an ultracold gas of bosonic (88)Sr. A systematic measurement of three resonances allows precise determinations of the optical Feshbach resonance strength and scaling law, in agreement with coupled-channel theory. Resonant enhancement of the complex scattering length leads to thermalization mediated by elastic and inelastic collisions in an otherwise ideal gas. Optical Feshbach resonance could be used to control atomic interactions with high spatial and temporal resolution.

Transport of a Bose gas in 1D disordered lattices at the fluid-insulator transition.

PubMed

Tanzi, Luca; Lucioni, Eleonora; Chaudhuri, Saptarishi; Gori, Lorenzo; Kumar, Avinash; D'Errico, Chiara; Inguscio, Massimo; Modugno, Giovanni

2013-09-13

We investigate the momentum-dependent transport of 1D quasicondensates in quasiperiodic optical lattices. We observe a sharp crossover from a weakly dissipative regime to a strongly unstable one at a disorder-dependent critical momentum. In the limit of nondisordered lattices the observations suggest a contribution of quantum phase slips to the dissipation. We identify a set of critical disorder and interaction strengths for which such critical momentum vanishes, separating a fluid regime from an insulating one. We relate our observation to the predicted zero-temperature superfluid-Bose glass transition.

Damping-free collective oscillations of a driven two-component Bose gas in optical lattices

NASA Astrophysics Data System (ADS)

Shchedrin, Gavriil; Jaschke, Daniel; Carr, Lincoln D.

2018-04-01

We explore the quantum many-body physics of a driven Bose-Einstein condensate in optical lattices. The laser field induces a gap in the generalized Bogoliubov spectrum proportional to the effective Rabi frequency. The lowest-lying modes in a driven condensate are characterized by zero group velocity and nonzero current. Thus, the laser field induces roton modes, which carry interaction in a driven condensate. We show that collective excitations below the energy of the laser-induced gap remain undamped, while above the gap they are characterized by a significantly suppressed Landau damping rate.

Quantum rotor model for a Bose-Einstein condensate of dipolar molecules.

PubMed

Armaitis, J; Duine, R A; Stoof, H T C

2013-11-22

We show that a Bose-Einstein condensate of heteronuclear molecules in the regime of small and static electric fields is described by a quantum rotor model for the macroscopic electric dipole moment of the molecular gas cloud. We solve this model exactly and find the symmetric, i.e., rotationally invariant, and dipolar phases expected from the single-molecule problem, but also an axial and planar nematic phase due to many-body effects. Investigation of the wave function of the macroscopic dipole moment also reveals squeezing of the probability distribution for the angular momentum of the molecules.

Emergence of a turbulent cascade in a quantum gas

NASA Astrophysics Data System (ADS)

Navon, Nir; Gaunt, Alexander L.; Smith, Robert P.; Hadzibabic, Zoran

2016-11-01

A central concept in the modern understanding of turbulence is the existence of cascades of excitations from large to small length scales, or vice versa. This concept was introduced in 1941 by Kolmogorov and Obukhov, and such cascades have since been observed in various systems, including interplanetary plasmas, supernovae, ocean waves and financial markets. Despite much progress, a quantitative understanding of turbulence remains a challenge, owing to the interplay between many length scales that makes theoretical simulations of realistic experimental conditions difficult. Here we observe the emergence of a turbulent cascade in a weakly interacting homogeneous Bose gas—a quantum fluid that can be theoretically described on all relevant length scales. We prepare a Bose-Einstein condensate in an optical box, drive it out of equilibrium with an oscillating force that pumps energy into the system at the largest length scale, study its nonlinear response to the periodic drive, and observe a gradual development of a cascade characterized by an isotropic power-law distribution in momentum space. We numerically model our experiments using the Gross-Pitaevskii equation and find excellent agreement with the measurements. Our experiments establish the uniform Bose gas as a promising new medium for investigating many aspects of turbulence, including the interplay between vortex and wave turbulence, and the relative importance of quantum and classical effects.

Efimov-driven phase transitions of the unitary Bose gas.

PubMed

Piatecki, Swann; Krauth, Werner

2014-03-20

Initially predicted in nuclear physics, Efimov trimers are bound configurations of three quantum particles that fall apart when any one of them is removed. They open a window into a rich quantum world that has become the focus of intense experimental and theoretical research, as the region of 'unitary' interactions, where Efimov trimers form, is now accessible in cold-atom experiments. Here we use a path-integral Monte Carlo algorithm backed up by theoretical arguments to show that unitary bosons undergo a first-order phase transition from a normal gas to a superfluid Efimov liquid, bound by the same effects as Efimov trimers. A triple point separates these two phases and another superfluid phase, the conventional Bose-Einstein condensate, whose coexistence line with the Efimov liquid ends in a critical point. We discuss the prospects of observing the proposed phase transitions in cold-atom systems.

Microcanonical fluctuations of the condensate in weakly interacting Bose gases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Idziaszek, Zbigniew

2005-05-15

We study fluctuations of the number of Bose condensed atoms in a weakly interacting homogeneous and trapped gases. For a homogeneous system we apply the particle-number-conserving formulation of the Bogoliubov theory and calculate the condensate fluctuations within the canonical and the microcanonical ensembles. We demonstrate that, at least in the low-temperature regime, predictions of the particle-number-conserving and traditional, nonconserving theory are identical, and lead to the anomalous scaling of fluctuations. Furthermore, the microcanonical fluctuations differ from the canonical ones by a quantity which scales normally in the number of particles, thus predictions of both ensembles are equivalent in the thermodynamicmore » limit. We observe a similar behavior for a weakly interacting gas in a harmonic trap. This is in contrast to the trapped, ideal gas, where microcanonical and canonical fluctuations are different in the thermodynamic limit.« less

Critical Point of a Weakly Interacting Two-Dimensional Bose Gas

NASA Astrophysics Data System (ADS)

Prokof'ev, Nikolay; Ruebenacker, Oliver; Svistunov, Boris

2002-03-01

We study the Berezinskii-Kosterlitz-Thouless transition in a We study the Berezinskii-Kosterlitz-Thouless transition in a weakly interacting 2D quantum Bose gas using the concept of universality and numerical simulations of the classical |ψ|^4-model on a lattice. The critical density and chemical potential are given by relations n_c=(mT/2π hbar^2) ln(ξ hbar^2/ mU) and μ_c=(mTU/π hbar^2) ln(ξ_μ hbar^2/ mU), where T is the temperature, m is the mass, and U is the effective interaction. The dimensionless constant ξ= 380 ± 3 is very large and thus any quantitative analysis of the experimental data crucially depends on its value. For ξ_μ our result is ξ_μ = 13.2 ± 0.4 . We also report the study of the quasi-condensate correlations at the critical point.

Three-dimensional imaging of the ultracold plasma formed in a supersonic molecular beam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schulz-Weiling, Markus; Grant, Edward

Double-resonant excitation of nitric oxide in a seeded supersonic molecular beam forms a state-selected Rydberg gas that evolves to form an ultracold plasma. This plasma travels with the propagation of the molecular beam in z over a variable distance as great as 600 mm to strike an imaging detector, which records the charge distribution in the dimensions, x and y. The ω{sub 1} + ω{sub 2} laser crossed molecular beam excitation geometry convolutes the axial Gaussian distribution of NO in the molecular beam with the Gaussian intensity distribution of the perpendicularly aligned laser beam to create an ellipsoidal volume of Rydbergmore » gas. Detected images describe the evolution of this initial density as a function of selected Rydberg gas initial principal quantum number, n{sub 0}, ω{sub 1} laser pulse energy (linearly related to Rydberg gas density, ρ{sub 0}) and flight time. Low-density Rydberg gases of lower principal quantum number produce uniformly expanding, ellipsoidal charge-density distributions. Increase either of n{sub 0} or ρ{sub 0} breaks the ellipsoidal symmetry of plasma expansion. The volume bifurcates to form repelling plasma volumes. The velocity of separation depends on n{sub 0} and ρ{sub 0} in a way that scales uniformly with ρ{sub e}, the density of electrons formed in the core of the Rydberg gas by prompt Penning ionization. Conditions under which this electron gas drives expansion in the long axis dimension of the ellipsoid favours the formation of counter-propagating shock waves.« less

76 FR 78642 - TransCanada Alaska Company, LLC; Notice of Public Scoping Meetings for the Planned Alaska...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-12-19

... Project (APP). The APP is a planned natural gas pipeline system that would transport gas produced on the Alaska North Slope to the Alaska-Canada border to connect with a pipeline system in Canada for onward..., 2051 Barter Avenue Kaktovik, AK. Dated: December 9, 2011. Kimberly D. Bose, Secretary. [FR Doc. 2011...

Condensation of an ideal gas obeying non-Abelian statistics.

PubMed

Mirza, Behrouz; Mohammadzadeh, Hosein

2011-09-01

We consider the thermodynamic geometry of an ideal non-Abelian gas. We show that, for a certain value of the fractional parameter and at the relevant maximum value of fugacity, the thermodynamic curvature has a singular point. This indicates a condensation such as Bose-Einstein condensation for non-Abelian statistics and we work out the phase transition temperature in various dimensions.

Fluctuations in non-ideal pion gas with dynamically fixed particle number

NASA Astrophysics Data System (ADS)

Kolomeitsev, E. E.; Voskresensky, D. N.

2018-05-01

We consider a non-ideal hot pion gas with the dynamically fixed number of particles in the model with the λϕ4 interaction. The effective Lagrangian for the description of such a system is obtained after dropping the terms responsible for the change of the total particle number. Reactions π+π- ↔π0π0, which determine the isospin balance of the medium, are permitted. Within the self-consistent Hartree approximation we compute the effective pion mass, thermodynamic characteristics of the system and the variance of the particle number at temperatures above the critical point of the induced Bose-Einstein condensation when the pion chemical potential reaches the value of the effective pion mass. We analyze conditions for the condensate formation in the process of thermalization of an initially non-equilibrium pion gas. The normalized variance of the particle number increases with a temperature decrease but remains finite in the critical point of the Bose-Einstein condensation. This is due to the non-perturbative account of the interaction and is in contrast to the ideal-gas case. In the kinetic regime of the condensate formation the variance is shown to stay finite also.

Strong-coupling Bose polarons out of equilibrium: Dynamical renormalization-group approach

NASA Astrophysics Data System (ADS)

Grusdt, Fabian; Seetharam, Kushal; Shchadilova, Yulia; Demler, Eugene

2018-03-01

When a mobile impurity interacts with a surrounding bath of bosons, it forms a polaron. Numerous methods have been developed to calculate how the energy and the effective mass of the polaron are renormalized by the medium for equilibrium situations. Here, we address the much less studied nonequilibrium regime and investigate how polarons form dynamically in time. To this end, we develop a time-dependent renormalization-group approach which allows calculations of all dynamical properties of the system and takes into account the effects of quantum fluctuations in the polaron cloud. We apply this method to calculate trajectories of polarons following a sudden quench of the impurity-boson interaction strength, revealing how the polaronic cloud around the impurity forms in time. Such trajectories provide additional information about the polaron's properties which are challenging to extract directly from the spectral function measured experimentally using ultracold atoms. At strong couplings, our calculations predict the appearance of trajectories where the impurity wavers back at intermediate times as a result of quantum fluctuations. Our method is applicable to a broader class of nonequilibrium problems. As a check, we also apply it to calculate the spectral function and find good agreement with experimental results. At very strong couplings, we predict that quantum fluctuations lead to the appearance of a dark continuum with strongly suppressed spectral weight at low energies. While our calculations start from an effective Fröhlich Hamiltonian describing impurities in a three-dimensional Bose-Einstein condensate, we also calculate the effects of additional terms in the Hamiltonian beyond the Fröhlich paradigm. We demonstrate that the main effect of these additional terms on the attractive side of a Feshbach resonance is to renormalize the coupling strength of the effective Fröhlich model.

Ultracold Mixtures of Rubidium and Ytterbium for Open Quantum System Engineering

DTIC Science & Technology

2014-06-01

was replaced with a standard nipple since the actual thermal conduction is comparable. Second, the collimation tube (5 mm ID x 15 cm length) was...Presumably, there is some sort of thin layer coating the Yb which must first be driven off. The helium buffer gas serves to shorten the mean free...path below the line-of-sight distance to the windows, and we can leave them at room temperature without coating them with Yb. The buffer gas causes

The quantum computer game: citizen science

NASA Astrophysics Data System (ADS)

Damgaard, Sidse; Mølmer, Klaus; Sherson, Jacob

2013-05-01

Progress in the field of quantum computation is hampered by daunting technical challenges. Here we present an alternative approach to solving these by enlisting the aid of computer players around the world. We have previously examined a quantum computation architecture involving ultracold atoms in optical lattices and strongly focused tweezers of light. In The Quantum Computer Game (see http://www.scienceathome.org/), we have encapsulated the time-dependent Schrödinger equation for the problem in a graphical user interface allowing for easy user input. Players can then search the parameter space with real-time graphical feedback in a game context with a global high-score that rewards short gate times and robustness to experimental errors. The game which is still in a demo version has so far been tried by several hundred players. Extensions of the approach to other models such as Gross-Pitaevskii and Bose-Hubbard are currently under development. The game has also been incorporated into science education at high-school and university level as an alternative method for teaching quantum mechanics. Initial quantitative evaluation results are very positive. AU Ideas Center for Community Driven Research, CODER.

Equilibrium polymerization on the equivalent-neighbor lattice

NASA Technical Reports Server (NTRS)

Kaufman, Miron

1989-01-01

The equilibrium polymerization problem is solved exactly on the equivalent-neighbor lattice. The Flory-Huggins (Flory, 1986) entropy of mixing is exact for this lattice. The discrete version of the n-vector model is verified when n approaches 0 is equivalent to the equal reactivity polymerization process in the whole parameter space, including the polymerized phase. The polymerization processes for polymers satisfying the Schulz (1939) distribution exhibit nonuniversal critical behavior. A close analogy is found between the polymerization problem of index the Schulz r and the Bose-Einstein ideal gas in d = -2r dimensions, with the critical polymerization corresponding to the Bose-Einstein condensation.

Maxwell's Demon at work: Two types of Bose condensate fluctuations in power-law traps.

PubMed

Grossmann, S; Holthaus, M

1997-11-10

After discussing the idea underlying the Maxwell's Demon ensemble, we employ this ensemble for calculating fluctuations of ideal Bose gas condensates in traps with power-law single-particle energy spectra. Two essentially different cases have to be distinguished. If the heat capacity is continuous at the condensation point, the fluctuations of the number of condensate particles vanish linearly with temperature, independent of the trap characteristics. In this case, microcanonical and canonical fluctuations are practically indistinguishable. If the heat capacity is discontinuous, the fluctuations vanish algebraically with temperature, with an exponent determined by the trap, and the micro-canonical fluctuations are lower than their canonical counterparts.

Impact of the Injection Protocol on an Impurity's Stationary State

NASA Astrophysics Data System (ADS)

Gamayun, Oleksandr; Lychkovskiy, Oleg; Burovski, Evgeni; Malcomson, Matthew; Cheianov, Vadim V.; Zvonarev, Mikhail B.

2018-06-01

We examine stationary-state properties of an impurity particle injected into a one-dimensional quantum gas. We show that the value of the impurity's end velocity lies between zero and the speed of sound in the gas and is determined by the injection protocol. This way, the impurity's constant motion is a dynamically emergent phenomenon whose description goes beyond accounting for the kinematic constraints of the Landau approach to superfluidity. We provide exact analytic results in the thermodynamic limit and perform finite-size numerical simulations to demonstrate that the predicted phenomena are within the reach of the ultracold gas experiments.

Homogeneous Atomic Fermi Gases

NASA Astrophysics Data System (ADS)

Mukherjee, Biswaroop; Yan, Zhenjie; Patel, Parth B.; Hadzibabic, Zoran; Yefsah, Tarik; Struck, Julian; Zwierlein, Martin W.

2017-03-01

We report on the creation of homogeneous Fermi gases of ultracold atoms in a uniform potential. In the momentum distribution of a spin-polarized gas, we observe the emergence of the Fermi surface and the saturated occupation of one particle per momentum state: the striking consequence of Pauli blocking in momentum space for a degenerate gas. Cooling a spin-balanced Fermi gas at unitarity, we create homogeneous superfluids and observe spatially uniform pair condensates. For thermodynamic measurements, we introduce a hybrid potential that is harmonic in one dimension and uniform in the other two. The spatially resolved compressibility reveals the superfluid transition in a spin-balanced Fermi gas, saturation in a fully polarized Fermi gas, and strong attraction in the polaronic regime of a partially polarized Fermi gas.

The Coldest Place in the Universe: Probing the Ultra-cold Outflow and Dusty Disk in the Boomerang Nebula

NASA Astrophysics Data System (ADS)

Sahai, R.; Vlemmings, W. H. T.; Nyman, L.-Å.

2017-06-01

Our Cycle 0 ALMA observations confirmed that the Boomerang Nebula is the coldest known object in the universe, with a massive high-speed outflow that has cooled significantly below the cosmic background temperature. Our new CO 1-0 data reveal heretofore unseen distant regions of this ultra-cold outflow, out to ≳120,000 au. We find that in the ultra-cold outflow, the mass-loss rate (\\dot{M}) increases with radius, similar to its expansion velocity (V)—taking V\\propto r, we find \\dot{M}\\propto {r}0.9{--2.2}. The mass in the ultra-cold outflow is ≳ 3.3 M ⊙, and the Boomerang’s main-sequence progenitor mass is ≳ 4 M ⊙. Our high angular resolution (˜ 0\\buildrel{\\prime\\prime}\\over{.} 3) CO J = 3-2 map shows the inner bipolar nebula’s precise, highly collimated shape, and a dense central waist of size (FWHM) ˜1740 au × 275 au. The molecular gas and the dust as seen in scattered light via optical Hubble Space Telescope imaging show a detailed correspondence. The waist shows a compact core in thermal dust emission at 0.87-3.3 mm, which harbors (4{--}7)× {10}-4 M ⊙ of very large (˜millimeter-to-centimeter sized), cold (˜ 20{--}30 K) grains. The central waist (assuming its outer regions to be expanding) and fast bipolar outflow have expansion ages of ≲ 1925 {years} and ≤slant 1050 {years}: the “jet-lag” (I.e., torus age minus the fast-outflow age) in the Boomerang supports models in which the primary star interacts directly with a binary companion. We argue that this interaction resulted in a common-envelope configuration, while the Boomerang’s primary was an RGB or early-AGB star, with the companion finally merging into the primary’s core, and ejecting the primary’s envelope that now forms the ultra-cold outflow.

Developing density functional theory for Bose-Einstein condensates. The case of chemical bonding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Putz, Mihai V., E-mail: mvputz@cbg.uvt.ro

Since the nowadays growing interest in Bose-Einstein condensates due to the expanded experimental evidence on various atomic systems within optical lattices in weak and strong coupling regimes, the connection with Density Functional Theory is firstly advanced within the mean field framework at three levels of comprehension: the many-body normalization condition, Thomas-Fermi limit, and the chemical hardness closure with the inter-bosonic strength and universal Hohenberg-Kohn functional. As an application the traditional Heitler-London quantum mechanical description of the chemical bonding for homopolar atomic systems is reloaded within the non-linear Schrödinger (Gross-Pitaevsky) Hamiltonian; the results show that a two-fold energetic solution is registeredmore » either for bonding and antibonding states, with the bosonic contribution being driven by the square of the order parameter for the Bose-Einstein condensate density in free (gas) motion, while the associate wave functions remain as in classical molecular orbital model.« less

Impurity in a Bose-Einstein condensate: Study of the attractive and repulsive branch using quantum Monte Carlo methods

NASA Astrophysics Data System (ADS)

Ardila, L. A. Peña; Giorgini, S.

2015-09-01

We investigate the properties of an impurity immersed in a dilute Bose gas at zero temperature using quantum Monte Carlo methods. The interactions between bosons are modeled by a hard-sphere potential with scattering length a , whereas the interactions between the impurity and the bosons are modeled by a short-range, square-well potential where both the sign and the strength of the scattering length b can be varied by adjusting the well depth. We characterize the attractive and the repulsive polaron branch by calculating the binding energy and the effective mass of the impurity. Furthermore, we investigate the structural properties of the bath, such as the impurity-boson contact parameter and the change of the density profile around the impurity. At the unitary limit of the impurity-boson interaction, we find that the effective mass of the impurity remains smaller than twice its bare mass, while the binding energy scales with ℏ2n2 /3/m , where n is the density of the bath and m is the common mass of the impurity and the bosons in the bath. The implications for the phase diagram of binary Bose-Bose mixtures at low concentrations are also discussed.

Probing and Manipulating Ultracold Fermi Superfluids

NASA Astrophysics Data System (ADS)

Jiang, Lei

Ultracold Fermi gas is an exciting field benefiting from atomic physics, optical physics and condensed matter physics. It covers many aspects of quantum mechanics. Here I introduce some of my work during my graduate study. We proposed an optical spectroscopic method based on electromagnetically-induced transparency (EIT) as a generic probing tool that provides valuable insights into the nature of Fermi paring in ultracold Fermi gases of two hyperfine states. This technique has the capability of allowing spectroscopic response to be determined in a nearly non-destructive manner and the whole spectrum may be obtained by scanning the probe laser frequency faster than the lifetime of the sample without re-preparing the atomic sample repeatedly. Both quasiparticle picture and pseudogap picture are constructed to facilitate the physical explanation of the pairing signature in the EIT spectra. Motivated by the prospect of realizing a Fermi gas of 40K atoms with a synthetic non-Abelian gauge field, we investigated theoretically BEC-HCS crossover physics in the presence of a Rashba spin-orbit coupling in a system of two-component Fermi gas with and without a Zeeman field that breaks the population balance. A new bound state (Rashba pair) emerges because of the spin-orbit interaction. We studied the properties of Rashba pairs using a standard pair fluctuation theory. As the two-fold spin degeneracy is lifted by spin-orbit interaction, bound pairs with mixed singlet and triplet pairings (referred to as rashbons) emerge, leading to an anisotropic superfluid. We discussed in detail the experimental signatures for observing the condensation of Rashba pairs by calculating various physical observables which characterize the properties of the system and can be measured in experiment. The role of impurities as experimental probes in the detection of quantum material properties is well appreciated. Here we studied the effect of a single classical impurity in trapped ultracold Fermi superfluids. Although a non-magnetic impurity does not change macroscopic properties of s-wave Fermi superfluids, depending on its shape and strength, a magnetic impurity can induce single or multiple mid-gap bound states. The multiple mid-gap states could coincide with the development of a Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase within the superfluid. As an analog of the Scanning Tunneling Microscope, we proposed a modified radio frequency spectroscopic method to measure the focal density of states which can be employed to detect these states and other quantum phases of cold atoms. A key result of our self consistent Bogoliubov-de Gennes calculations is that a magnetic impurity can controllably induce an FFLO state at currently accessible experimental parameters.

Analytical results for the time-dependent current density distribution of expanding ultracold gases after a sudden change of the confining potential

NASA Astrophysics Data System (ADS)

Boumaza, R.; Bencheikh, K.

2017-12-01

Using the so-called operator product expansion to lowest order, we extend the work in Campbell et al (2015 Phys. Rev. Lett 114 125302) by deriving a simple analytical expression for the long-time asymptotic one-body reduced density matrix during free expansion for a one-dimensional system of bosons with large atom number interacting through a repulsive delta potential initially confined by a potential well. This density matrix allows direct access to the momentum distribution and also to the mass current density. For initially confining power-law potentials we give explicit expressions, in the limits of very weak and very strong interaction, for the current density distributions during the free expansion. In the second part of the work we consider the expansion of ultracold gas from a confining harmonic trap to another harmonic trap with a different frequency. For the case of a quantum impenetrable gas of bosons (a Tonks-Girardeau gas) with a given atom number, we present an exact analytical expression for the mass current distribution (mass transport) after release from one harmonic trap to another harmonic trap. It is shown that, for a harmonically quenched Tonks-Girardeau gas, the current distribution is a suitable collective observable and under the weak quench regime, it exhibits oscillations at the same frequencies as those recently predicted for the peak momentum distribution in the breathing mode. The analysis is extended to other possible quenched systems.

Holographic method for site-resolved detection of a 2D array of ultracold atoms

NASA Astrophysics Data System (ADS)

Hoffmann, Daniel Kai; Deissler, Benjamin; Limmer, Wolfgang; Hecker Denschlag, Johannes

2016-08-01

We propose a novel approach to site-resolved detection of a 2D gas of ultracold atoms in an optical lattice. A near-resonant laser beam is coherently scattered by the atomic array, and after passing a lens its interference pattern is holographically recorded by superimposing it with a reference laser beam on a CCD chip. Fourier transformation of the recorded intensity pattern reconstructs the atomic distribution in the lattice with single-site resolution. The holographic detection method requires only about two hundred scattered photons per atom in order to achieve a high reconstruction fidelity of 99.9 %. Therefore, additional cooling during detection might not be necessary even for light atomic elements such as lithium. Furthermore, first investigations suggest that small aberrations of the lens can be post-corrected in imaging processing.

Particle statistics and lossy dynamics of ultracold atoms in optical lattices

NASA Astrophysics Data System (ADS)

Yago Malo, J.; van Nieuwenburg, E. P. L.; Fischer, M. H.; Daley, A. J.

2018-05-01

Experimental control over ultracold quantum gases has made it possible to investigate low-dimensional systems of both bosonic and fermionic atoms. In closed one-dimensional systems there are many similarities in the dynamics of local quantities for spinless fermions and strongly interacting "hard-core" bosons, which on a lattice can be formalized via a Jordan-Wigner transformation. In this study, we analyze the similarities and differences for spinless fermions and hard-core bosons on a lattice in the presence of particle loss. The removal of a single fermion causes differences in local quantities compared with the bosonic case because of the different particle exchange symmetry in the two cases. We identify deterministic and probabilistic signatures of these dynamics in terms of local particle density, which could be measured in ongoing experiments with quantum gas microscopes.

Excitations in the Yang–Gaudin Bose gas

DOE PAGES

Robinson, Neil J.; Konik, Robert M.

2017-06-01

Here, we study the excitation spectrum of two-component delta-function interacting bosons confined to a single spatial dimension, the Yang–Gaudin Bose gas. We show that there are pronounced finite-size effects in the dispersion relations of excitations, perhaps best illustrated by the spinon single particle dispersion which exhibits a gap at 2k F and a finite-momentum roton-like minimum. Such features occur at energies far above the finite volume excitation gap, vanish slowly as 1/L for fixed spinon number, and can persist to the thermodynamic limit at fixed spinon density. Features such as the 2k F gap also persist to multi-particle excitation continua. Our results show that excitations in the finite system can behave in a qualitatively different manner to analogous excitations in the thermodynamic limit. The Yang–Gaudin Bose gas is also host to multi-spinon bound states, known asmore » $$\\Lambda$$ -strings. We study these excitations both in the thermodynamic limit under the string hypothesis and in finite size systems where string deviations are taken into account. In the zero-temperature limit we present a simple relation between the length n $$\\Lambda$$-string dressed energies $$\\epsilon_n(\\lambda)$$ and the dressed energy $$\\epsilon(k)$$. We solve the Yang–Yang–Takahashi equations numerically and compare to the analytical solution obtained under the strong couple expansion, revealing that the length n $$\\Lambda$$ -string dressed energy is Lorentzian over a wide range of real string centers λ in the vicinity of $$\\lambda = 0$$ . We then examine the finite size effects present in the dispersion of the two-spinon bound states by numerically solving the Bethe ansatz equations with string deviations.« less

Second sound and the density response function in uniform superfluid atomic gases

NASA Astrophysics Data System (ADS)

Hu, H.; Taylor, E.; Liu, X.-J.; Stringari, S.; Griffin, A.

2010-04-01

Recently, there has been renewed interest in second sound in superfluid Bose and Fermi gases. By using two-fluid hydrodynamic theory, we review the density response χnn(q, ω) of these systems as a tool to identify second sound in experiments based on density probes. Our work generalizes the well-known studies of the dynamic structure factor S(q, ω) in superfluid 4He in the critical region. We show that, in the unitary limit of uniform superfluid Fermi gases, the relative weight of second versus first sound in the compressibility sum rule is given by the Landau-Placzek ratio \\epsilon_{\\mathrm{LP}}\\equiv (\\bar{c}_p-\\bar{c}_v)/\\bar{c}_v for all temperatures below Tc. In contrast to superfluid 4He, epsilonLP is much larger in strongly interacting Fermi gases, being already of order unity for T~0.8Tc, thereby providing promising opportunities to excite second sound with density probes. The relative weights of first and second sound are quite different in S(q, ω) (measured in pulse propagation studies) as compared with Imχnn(q, ω) (measured in two-photon Bragg scattering). We show that first and second sound in S(q, ω) in a strongly interacting Bose-condensed gas are similar to those in a Fermi gas at unitarity. However, in a weakly interacting Bose gas, first and second sound are mainly uncoupled oscillations of the thermal cloud and condensate, respectively, and second sound has most of the spectral weight in S(q, ω). We also discuss the behaviour of the superfluid and normal fluid velocity fields involved in first and second sound.

Bose-Einstein condensation of light: general theory.

PubMed

Sob'yanin, Denis Nikolaevich

2013-08-01

A theory of Bose-Einstein condensation of light in a dye-filled optical microcavity is presented. The theory is based on the hierarchical maximum entropy principle and allows one to investigate the fluctuating behavior of the photon gas in the microcavity for all numbers of photons, dye molecules, and excitations at all temperatures, including the whole critical region. The master equation describing the interaction between photons and dye molecules in the microcavity is derived and the equivalence between the hierarchical maximum entropy principle and the master equation approach is shown. The cases of a fixed mean total photon number and a fixed total excitation number are considered, and a much sharper, nonparabolic onset of a macroscopic Bose-Einstein condensation of light in the latter case is demonstrated. The theory does not use the grand canonical approximation, takes into account the photon polarization degeneracy, and exactly describes the microscopic, mesoscopic, and macroscopic Bose-Einstein condensation of light. Under certain conditions, it predicts sub-Poissonian statistics of the photon condensate and the polarized photon condensate, and a universal relation takes place between the degrees of second-order coherence for these condensates. In the macroscopic case, there appear a sharp jump in the degrees of second-order coherence, a sharp jump and kink in the reduced standard deviations of the fluctuating numbers of photons in the polarized and whole condensates, and a sharp peak, a cusp, of the Mandel parameter for the whole condensate in the critical region. The possibility of nonclassical light generation in the microcavity with the photon Bose-Einstein condensate is predicted.

Pairing fluctuations and the superfluid density through the BCS-BEC crossover

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taylor, E.; Griffin, A.; Fukushima, N.

2006-12-15

We derive an expression for the superfluid density of a uniform two-component Fermi gas through the BCS-BEC crossover in terms of the thermodynamic potential in the presence of an imposed superfluid flow. Treating the pairing fluctuations in a Gaussian approximation following the approach of Nozieres and Schmitt-Rink, we use this definition of {rho}{sub s} to obtain an explicit result which is valid at finite temperatures and over the full BCS-BEC crossover. It is crucial that the BCS gap {delta}, the chemical potential {mu}, and {rho}{sub s} all include the effect of fluctuations at the same level in a self-consistent manner.more » We show that the normal fluid density {rho}{sub n}{identical_to}n-{rho}{sub s} naturally separates into a sum of contributions from Fermi BCS quasiparticles ({rho}{sub n}{sup F}) and Bose collective modes ({rho}{sub n}{sup B}). The expression for {rho}{sub n}{sup F} is just Landau's formula for a BCS Fermi superfluid but now calculated over the BCS-BEC crossover. The expression for the Bose contribution {rho}{sub n}{sup B} is more complicated and only reduces to Landau's formula for a Bose superfluid in the extreme BEC limit, where all the fermions have formed stable Bose pairs and the Bogoliubov excitations of the associated molecular Bose condensate are undamped. In a companion paper, we present numerical calculations of {rho}{sub s} using an expression equivalent to the one derived in this paper, over the BCS-BEC crossover, including unitarity, and at finite temperatures.« less

Non-Abelian gauge fields

NASA Astrophysics Data System (ADS)

Gerbier, Fabrice; Goldman, Nathan; Lewenstein, Maciej; Sengstock, Klaus

2013-07-01

Building a universal quantum computer is a central goal of emerging quantum technologies, which has the potential to revolutionize science and technology. Unfortunately, this future does not seem to be very close at hand. However, quantum computers built for a special purpose, i.e. quantum simulators , are currently developed in many leading laboratories. Many schemes for quantum simulation have been proposed and realized using, e.g., ultracold atoms in optical lattices, ultracold trapped ions, atoms in arrays of cavities, atoms/ions in arrays of traps, quantum dots, photonic networks, or superconducting circuits. The progress in experimental implementations is more than spectacular. Particularly interesting are those systems that simulate quantum matter evolving in the presence of gauge fields. In the quantum simulation framework, the generated (synthetic) gauge fields may be Abelian, in which case they are the direct analogues of the vector potentials commonly associated with magnetic fields. In condensed matter physics, strong magnetic fields lead to a plethora of fascinating phenomena, among which the most paradigmatic is perhaps the quantum Hall effect. The standard Hall effect consists in the appearance of a transverse current, when a longitudinal voltage difference is applied to a conducting sample. For quasi-two-dimensional semiconductors at low temperatures placed in very strong magnetic fields, the transverse conductivity, the ratio between the transverse current and the applied voltage, exhibits perfect and robust quantization, independent for instance of the material or of its geometry. Such an integer quantum Hall effect, is now understood as a deep consequence of underlying topological order. Although such a system is an insulator in the bulk, it supports topologically robust edge excitations which carry the Hall current. The robustness of these chiral excitations against backscattering explains the universality of the quantum Hall effect. Another interesting and related effect, which arises from the interplay between strong magnetic field and lattice potentials, is the famous Hofstadter butterfly: the energy spectrum of a single particle moving on a lattice and subjected to a strong magnetic field displays a beautiful fractal structure as a function of the magnetic flux penetrating each elementary plaquette of the lattice. When the effects of interparticle interactions become dominant, two-dimensional gases of electrons exhibit even more exotic behaviour leading to the fractional quantum Hall effect. In certain conditions such a strongly interacting electron gas may form a highly correlated state of matter, the prototypical example being the celebrated Laughlin quantum liquid. Even more fascinating is the behaviour of bulk excitations (quasi-hole and quasi-particles): they are neither fermionic nor bosonic, but rather behave as anyons with fractional statistics intermediate between the two. Moreover, for some specific filling factors (ratio between the electronic density and the flux density), these anyons are proven to have an internal structure (several components) and non-Abelian braiding properties. Many of the above statements concern theoretical predictions—they have never been observed in condensed matter systems. For instance, the fractional values of the Hall conductance is seen as a direct consequence of the fractional statistics, but to date direct observation of anyons has not been possible in two-dimensional semiconductors. Realizing these predictions in experiments with atoms, ions, photons etc, which potentially allow the experimentalist to perform measurements complementary to those made in condensed matter systems, is thus highly desirable! Non-Abelian gauge fields couple the motional states of the particles to their internal degrees of freedom (such as hyperfine states for atoms or ions, electronic spins for electrons, etc). In this sense external non-Abelian fields extend the concept of spin-orbit coupling (Rashba and Dresselhaus couplings), familiar from AMO and condensed matter physics. They lead to yet another variety of fascinating phenomena such as the quantum spin Hall effect, three-dimensional topological insulators, topological superconductors and superfluids of various kinds. One also expects here the appearance of excitations in a form of topological edge states that can support robust transport, or entangled Majorana fermions in the case of topological superconductors or superfluids. Again, while many kinds of topological insulators have been realized in condensed matter systems, a controlled way of creating them in AMO systems and studying quantum phase transitions between various kinds of them is obviously very appealing and challenging. The various systems listed so far correspond to static gauge fields, which are externally imposed by the experimentalists. Even more fascinating is the possibility of generating synthetically dynamical gauge fields, i.e. gauge fields that evolve in time according to an interacting gauge theory, e.g., a full lattice gauge theory (LGT). These dynamical gauge fields can also couple to matter fields, allowing the quantum simulation of such complex systems (notoriously hard to simulate using 'traditional' computers), which are particularly relevant for modern high-energy physics. So far, most of the theoretical proposals concern the simulation of Abelian gauge theories, however, several groups have recently proposed extensions to the non-Abelian scenarios. The scope of the present focused issue of Journal of Physics B is to cover all of these developments, with particular emphasis on the non-Abelian gauge fields. The 14 papers in this issue include contributions from the leading theory groups working in this field; we believe that this collection will provide the reference set for quantum simulations of gauge fields. Although the special issue contains exclusively theoretical proposals and studies, it should be stressed that the progress in experimental studies of artificial Abelian and non-Abelian gauge fields in recent years has been simply spectacular. Multiple leading groups are working on this subject and have already obtained a lot of seminal results. The papers in the special issue are ordered according to the date of acceptance. The issue opens with a review article by Zhou et al [1] on unconventional states of bosons with synthetic spin-orbit coupling. Next, the paper by Maldonado-Mundo et al [2] studies ultracold Fermi gases with artificial Rashba spin-orbit coupling in a 2D gas. Anderson and Charles [3], in contrast, discuss a three-dimensional spin-orbit coupling in a trap. Orth et al [4] investigate correlated topological phases and exotic magnetism with ultracold fermions, again in the presence of artificial gauge fields. The paper of Nascimbène [5] does not address the synthetic gauge fields directly, but describes an experimental proposal for realizing one-dimensional topological superfluids with ultracold atomic gases; obviously, this problem is well situated in the general and growing field of topological superfluids, in particular those realized in the presence of non-Abelian gauge fields/spin-orbit coupling. Graß et al [6] consider in their paper fractional quantum Hall states of a Bose gas with spin-orbit coupling induced by a laser. Particular attention is drawn here to the possibility of realizing states with non-Abelian anyonic excitations. Zheng et al [7] study properties of Bose gases with Raman-induced spin-orbit coupling. Kiffner et al [8] in their paper touch on another kind of system, namely ultracold Rydberg atoms. In particular they study the generation of Abelian and non-Abelian gauge fields in dipole-dipole interacting Rydberg atoms. The behaviour of fermions in synthetic non-Abelian gauge potentials is discussed by Shenoy and Vyasanakere [9]. The paper starts with the study of Rashbon condensates (i.e. Bose condensates in the presence of Rashba coupling) and also introduces novel kinds of exotic Hamiltonians. Goldman et al [10] propose a concrete setup for realizing arbitrary non-Abelian gauge potentials in optical square lattices; they discuss how such synthetic gauge fields can be exploited to generate Chern insulators. Zygelman [11], similarly as Kiffner et al [8], discusses in his paper non-Abelian gauge fields in Rydberg systems. Marchukov et al [12] return to the subject of spin-orbit coupling, and investigate spectral gaps of spin-orbit coupled particles in the realistic situations of deformed traps. The last two papers, in contrast, are devoted to different subjects. Edmonds et al [13] consider a 'dynamical' density-dependent gauge potential, and study the Josephson effect in a Bose-Einstein condensate subject to such a potential. Last, but not least, Mazzucchi et al [14] study the properties of semimetal-superfluid quantum phase transitions in 3D lattices with Dirac points. References [1] Zhou X, Li Y, Cai Z and Wu C 2013 J. Phys. B: At. Mol. Opt. Phys. 46 134001 [2] Maldonado-Mundo D, Öhberg P and Valiente M 2013 J. Phys. B: At. Mol. Opt. Phys. 46 134002 [3] Anderson B M and Clark C W 2013 J. Phys. B: At. Mol. Opt. Phys. 46 134003 [4] Orth P P, Cocks D, Rachel S, Buchhold M, Le Hur K and Hofstetter W 2013 J. Phys. B: At. Mol. Opt. Phys. 46 134004 [5] Nascimbène S 2013 J. Phys. B: At. Mol. Opt. Phys. 46 134005 [6] Graß T, Juliá-Díaz B, Burrello M and Lewenstein M 2013 J. Phys. B: At. Mol. Opt. Phys. 46 134006 [7] Zheng W, Yu Z-Q, Cui X and Zhai H 2013 J. Phys. B: At. Mol. Opt. Phys. 46 134007 [8] Kiffner M, Li W and Jaksch D 2013 J. Phys. B: At. Mol. Opt. Phys. 46 134008 [9] Shenoy V B and Vyasanakere J P 2013 J. Phys. B: At. Mol. Opt. Phys. 46 134009 [10] Goldman N, Gerbier F and Lewenstein M 2013 J. Phys. B: At. Mol. Opt. Phys. 46 134010 [11] Zygelman B 2013 J. Phys. B: At. Mol. Opt. Phys. 46 134011 [12] Marchukov O V, Volosniev A G, Fedorov D V, Jensen A S and Zinner N T 2013 J. Phys. B: At. Mol. Opt. Phys. 46 134012 [13] Edmonds M J, Valiente M and Öhberg P 2013 J. Phys. B: At. Mol. Opt. Phys. 46 134013 [14] Mazzucchi G, Lepori L and Trombettoni A 2013 J. Phys. B: At. Mol. Opt. Phys. 46 134014

Dynamics of Three-Body Correlations in Quenched Unitary Bose Gases

NASA Astrophysics Data System (ADS)

Colussi, V. E.; Corson, J. P.; D'Incao, J. P.

2018-03-01

We investigate dynamical three-body correlations in the Bose gas during the earliest stages of evolution after a quench to the unitary regime. The development of few-body correlations is theoretically observed by determining the two- and three-body contacts. We find that the growth of three-body correlations is gradual compared to two-body correlations. The three-body contact oscillates coherently, and we identify this as a signature of Efimov trimers. We show that the growth of three-body correlations depends nontrivially on parameters derived from both the density and Efimov physics. These results demonstrate the violation of scaling invariance of unitary bosonic systems via the appearance of log-periodic modulation of three-body correlations.

Spin imbalance effect on the Larkin-Ovchinnikov-Fulde-Ferrel state

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoshii, Ryosuke; Tsuchiya, Shunji; Research and Education Center for Natural Sciences, Keio University, 4-1-1 Hiyoshi, Kanagawa 223-8521

2011-07-01

We study spin imbalance effects on the Larkin-Ovchinnikov-Fulde-Ferrel (LOFF) state relevant for superconductors under a strong magnetic field and spin polarized ultracold Fermi gas. We obtain the exact solution for the condensates with arbitrary spin imbalance and the fermion spectrum perturbatively in the presence of small spin imbalance. We also obtain fermion zero mode exactly without perturbation theory.

Time-Dependent Wave Packet Dynamics Calculations of Cross Sections for Ultracold Scattering of Molecules

NASA Astrophysics Data System (ADS)

Huang, Jiayu; Liu, Shu; Zhang, Dong H.; Krems, Roman V.

2018-04-01

Because the de Broglie wavelength of ultracold molecules is very large, the cross sections for collisions of molecules at ultracold temperatures are always computed by the time-independent quantum scattering approach. Here, we report the first accurate time-dependent wave packet dynamics calculation for reactive scattering of ultracold molecules. Wave packet dynamics calculations can be applied to molecular systems with more dimensions and provide real-time information on the process of bond rearrangement and/or energy exchange in molecular collisions. Our work thus makes possible the extension of rigorous quantum calculations of ultracold reaction properties to polyatomic molecules and adds a new powerful tool for the study of ultracold chemistry.

Time-Dependent Wave Packet Dynamics Calculations of Cross Sections for Ultracold Scattering of Molecules.

PubMed

Huang, Jiayu; Liu, Shu; Zhang, Dong H; Krems, Roman V

2018-04-06

Because the de Broglie wavelength of ultracold molecules is very large, the cross sections for collisions of molecules at ultracold temperatures are always computed by the time-independent quantum scattering approach. Here, we report the first accurate time-dependent wave packet dynamics calculation for reactive scattering of ultracold molecules. Wave packet dynamics calculations can be applied to molecular systems with more dimensions and provide real-time information on the process of bond rearrangement and/or energy exchange in molecular collisions. Our work thus makes possible the extension of rigorous quantum calculations of ultracold reaction properties to polyatomic molecules and adds a new powerful tool for the study of ultracold chemistry.

Total cross sections for ultracold neutrons scattered from gases

DOE PAGES

Seestrom, Susan Joyce; Adamek, Evan R.; Barlow, Dave; ...

2017-01-30

Here, we have followed up on our previous measurements of upscattering of ultracold neutrons (UCNs) from a series of gases by making measurements of total cross sections on the following gases hydrogen, ethane, methane, isobutene, n-butane, ethylene, water vapor, propane, neopentane, isopropyl alcohol, and 3He. The values of these cross sections are important for estimating the loss rate of trapped neutrons due to residual gas and are relevant to neutron lifetime measurements using UCNs. The effects of the UCN velocity and path-length distributions were accounted for in the analysis using a Monte Carlo transport code. Results are compared to ourmore » previous measurements and with the known absorption cross section for 3He scaled to our UCN energy. We find that the total cross sections for the hydrocarbon gases are reasonably described by a function linear in the number of hydrogen atoms in the molecule.« less

Generalized Stefan-Boltzmann Law

NASA Astrophysics Data System (ADS)

Montambaux, Gilles

2018-03-01

We reconsider the thermodynamic derivation by L. Boltzmann of the Stefan law and we generalize it for various different physical systems whose chemical potential vanishes. Being only based on classical arguments, therefore independent of the quantum statistics, this derivation applies as well to the saturated Bose gas in various geometries as to "compensated" Fermi gas near a neutrality point, such as a gas of Weyl Fermions. It unifies in the same framework the thermodynamics of many different bosonic or fermionic non-interacting gases which were until now described in completely different contexts.

Color superfluidity of neutral ultracold fermions in the presence of color-flip and color-orbit fields

NASA Astrophysics Data System (ADS)

Kurkcuoglu, Doga Murat; Sá de Melo, C. A. R.

2018-02-01

We describe how color superfluidity is modified in the presence of color-flip and color-orbit fields in the context of ultracold atoms and discuss connections between this problem and that of color superconductivity in quantum chromodynamics. We study the case of s -wave contact interactions between different colors and we identify several superfluid phases, with five being nodal and one being fully gapped. When our system is described in a mixed-color basis, the superfluid order parameter tensor is characterized by six independent components with explicit momentum dependence induced by color-orbit coupling. The nodal superfluid phases are topological in nature and the low-temperature phase diagram of the color-flip field versus the interaction parameter exhibits a pentacritical point, where all five nodal color superfluid phases converge. These results are in sharp contrast to the case of zero color-flip and color-orbit fields, where the system has perfect U(3) symmetry and possesses a superfluid phase that is characterized by fully gapped quasiparticle excitations with a single complex order parameter with no momentum dependence and by inert unpaired fermions representing a nonsuperfluid component. In the latter case, just a crossover between a Bardeen-Cooper-Schrieffer and a Bose-Einstein-condensation superfluid occurs. Furthermore, we analyze the order parameter tensor in a total pseudospin basis, investigate its momentum dependence in the singlet, triplet, and quintet sectors, and compare the results with the simpler case of spin-1/2 fermions in the presence of spin-flip and spin-orbit fields, where only singlet and triplet channels arise. Finally, we analyze in detail spectroscopic properties of color superfluids in the presence of color-flip and color-orbit fields, such as the quasiparticle excitation spectrum, momentum distribution, and density of states to help characterize all the encountered topological quantum phases, which can be realized in fermionic isotopes of lithium, potassium, and ytterbium atoms with three internal states trapped.

Bulk viscosity of strongly interacting matter in the relaxation time approximation

DOE PAGES

Czajka, Alina; Hauksson, Sigtryggur; Shen, Chun; ...

2018-04-24

Here, we show how thermal mean field effects can be incorporated consistently in the hydrodynamical modeling of heavy-ion collisions. The nonequilibrium correction to the distribution function resulting from a temperature-dependent mass is obtained in a procedure which automatically satisfies the Landau matching condition and is thermodynamically consistent. The physics of the bulk viscosity is studied here for Boltzmann and Bose-Einstein gases within the Chapman-Enskog and 14-moment approaches in the relaxation time approximation. Constant and temperature-dependent masses are considered in turn. It is shown that, in the small mass limit, both methods lead to the same value of the ratio ofmore » the bulk viscosity to its relaxation time. The inclusion of a temperature-dependent mass leads to the emergence of the β λ function in that ratio, and it is of the expected parametric form for the Boltzmann gas, while for the Bose-Einstein case it is affected by the infrared cutoff. This suggests that the relaxation time approximation may be too crude to obtain a reliable form of ς/τ R for gases obeying Bose-Einstein statistics.« less

Bulk viscosity of strongly interacting matter in the relaxation time approximation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Czajka, Alina; Hauksson, Sigtryggur; Shen, Chun

Here, we show how thermal mean field effects can be incorporated consistently in the hydrodynamical modeling of heavy-ion collisions. The nonequilibrium correction to the distribution function resulting from a temperature-dependent mass is obtained in a procedure which automatically satisfies the Landau matching condition and is thermodynamically consistent. The physics of the bulk viscosity is studied here for Boltzmann and Bose-Einstein gases within the Chapman-Enskog and 14-moment approaches in the relaxation time approximation. Constant and temperature-dependent masses are considered in turn. It is shown that, in the small mass limit, both methods lead to the same value of the ratio ofmore » the bulk viscosity to its relaxation time. The inclusion of a temperature-dependent mass leads to the emergence of the β λ function in that ratio, and it is of the expected parametric form for the Boltzmann gas, while for the Bose-Einstein case it is affected by the infrared cutoff. This suggests that the relaxation time approximation may be too crude to obtain a reliable form of ς/τ R for gases obeying Bose-Einstein statistics.« less

Bulk viscosity of strongly interacting matter in the relaxation time approximation

NASA Astrophysics Data System (ADS)

Czajka, Alina; Hauksson, Sigtryggur; Shen, Chun; Jeon, Sangyong; Gale, Charles

2018-04-01

We show how thermal mean field effects can be incorporated consistently in the hydrodynamical modeling of heavy-ion collisions. The nonequilibrium correction to the distribution function resulting from a temperature-dependent mass is obtained in a procedure which automatically satisfies the Landau matching condition and is thermodynamically consistent. The physics of the bulk viscosity is studied here for Boltzmann and Bose-Einstein gases within the Chapman-Enskog and 14-moment approaches in the relaxation time approximation. Constant and temperature-dependent masses are considered in turn. It is shown that, in the small mass limit, both methods lead to the same value of the ratio of the bulk viscosity to its relaxation time. The inclusion of a temperature-dependent mass leads to the emergence of the βλ function in that ratio, and it is of the expected parametric form for the Boltzmann gas, while for the Bose-Einstein case it is affected by the infrared cutoff. This suggests that the relaxation time approximation may be too crude to obtain a reliable form of ζ /τR for gases obeying Bose-Einstein statistics.

The contact of a homogeneous unitary Fermi gas

NASA Astrophysics Data System (ADS)

Mukherjee, Biswaroop; Patel, Parth; Yan, Zhenjie; Fletcher, Richard; Struck, Julian; Zwierlein, Martin

2017-04-01

The contact is a fundamental quantity that measures the strength of short-range correlations in quantum gases. As one of its most important implications, it provides a link between the microscopic two-particle correlation function at small distance and the macroscopic thermodynamic properties of the gas. In particular, pairing and superfluidity in a unitary Fermi gas can be expected to leave its mark in behavior of the contact. Here we present measurements on the temperature dependence of the contact of a unitary Fermi gas across the superfluid transition. By trapping ultracold 6Li atoms in a potential that is homogeneous in two directions and harmonic in the third, we obtain radiofrequency spectra of the homogeneous gas at a high signal-to-noise ratio. We compare our data to existing, but often mutually excluding theoretical calculations for the strongly interacting Fermi gas.

Role of superconducting energy gap in extended BCS-Bose crossover theory

NASA Astrophysics Data System (ADS)

Chávez, I.; García, L. A.; de Llano, M.; Grether, M.

2017-10-01

The generalized Bose-Einstein condensation (GBEC) theory of superconductivity (SC) is briefly surveyed. It hinges on three distinct new ingredients: (i) Treatment of Cooper pairs (CPs) as actual bosons since they obey Bose statistics, in contrast to BCS pairs which do not obey Bose commutation relations; (ii) inclusion of two-hole Cooper pairs (2hCPs) on an equal footing with two-electron Cooper pairs (2eCPs), thus making this a complete boson-fermion (BF) model; and (iii) inclusion in the resulting ternary ideal BF gas with particular BF vertex interactions that drive boson formation/disintegration processes. GBEC subsumes as special cases both BCS (having its 50-50 symmetry of both kinds of CPs) and ordinary BEC theories (having no 2hCPs), as well as the now familiar BCS-Bose crossover theory. We extended the crossover theory with the explicit inclusion of 2hCPs and construct a phase diagram of Tc/TF versus n/nf, where Tc and TF are the critical and Fermi temperatures, n is the total number density and nf that of unbound electrons at T = 0. Also, with this extended crossover one can construct the energy gap Δ(T)/Δ(0) versus T/Tc for some elemental SCs by solving at least two equations numerically: a gap-like and a number equation. In 50-50 symmetry, the energy gap curve agrees quite well with experimental data. But ignoring 2hCPs altogether leads to the gap curve falling substantially below that with 50-50 symmetry which already fits the data quite well, showing that 2hCPs are indispensable to describe SCs.

Quantum Polarization Spectroscopy of Ultracold Spinor Gases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eckert, K.; Zawitkowski, L.; Sanpera, A.

2007-03-09

We propose a method for the detection of ground state quantum phases of spinor gases through a series of two quantum nondemolition measurements performed by sending off-resonant, polarized light pulses through the gas. Signatures of various mean-field as well as strongly correlated phases of F=1 and F=2 spinor gases obtained by detecting quantum fluctuations and mean values of polarization of transmitted light are identified.

Ionic Impurity in a Bose-Einstein Condensate at Submicrokelvin Temperatures

NASA Astrophysics Data System (ADS)

Kleinbach, K. S.; Engel, F.; Dieterle, T.; Löw, R.; Pfau, T.; Meinert, F.

2018-05-01

Rydberg atoms immersed in a Bose-Einstein condensate interact with the quantum gas via electron-atom and ion-atom interaction. To suppress the typically dominant electron-neutral interaction, Rydberg states with a principal quantum number up to n =190 are excited from a dense and tightly trapped micron-sized condensate. This allows us to explore a regime where the Rydberg orbit exceeds the size of the atomic sample by far. In this case, a detailed line shape analysis of the Rydberg excitation spectrum provides clear evidence for ion-atom interaction at temperatures well below a microkelvin. Our results may open up ways to enter the quantum regime of ion-atom scattering for the exploration of charged quantum impurities and associated polaron physics.

Observation of Spin Superfluidity in a Bose Gas Mixture

NASA Astrophysics Data System (ADS)

Fava, Eleonora; Bienaimé, Tom; Mordini, Carmelo; Colzi, Giacomo; Qu, Chunlei; Stringari, Sandro; Lamporesi, Giacomo; Ferrari, Gabriele

2018-04-01

The spin dynamics of a harmonically trapped Bose-Einstein condensed binary mixture of sodium atoms is experimentally investigated at finite temperature. In the collisional regime the motion of the thermal component is shown to be damped because of spin drag, while the two condensates exhibit a counterflow oscillation without friction, thereby providing direct evidence for spin superfluidity. Results are also reported in the collisionless regime where the spin components of both the condensate and thermal part oscillate without damping, their relative motion being driven by a mean-field effect. We also measure the static polarizability of the condensed and thermal parts and we find a large increase of the condensate polarizability with respect to the T =0 value, in agreement with the predictions of theory.

Quantum liquid droplets in a mixture of Bose-Einstein condensates

NASA Astrophysics Data System (ADS)

Cabrera, C. R.; Tanzi, L.; Sanz, J.; Naylor, B.; Thomas, P.; Cheiney, P.; Tarruell, L.

2018-01-01

Quantum droplets are small clusters of atoms self-bound by the balance of attractive and repulsive forces. Here, we report on the observation of droplets solely stabilized by contact interactions in a mixture of two Bose-Einstein condensates. We demonstrate that they are several orders of magnitude more dilute than liquid helium by directly measuring their size and density via in situ imaging. We show that the droplets are stablized against collapse by quantum fluctuations and that they require a minimum atom number to be stable. Below that number, quantum pressure drives a liquid-to-gas transition that we map out as a function of interaction strength. These ultradilute isotropic liquids remain weakly interacting and constitute an ideal platform to benchmark quantum many-body theories.

Transport in a capacitive ultracold atomtronic circuit

NASA Astrophysics Data System (ADS)

Eller, Benjamin; Warren, Kayla; Eckel, Stephen; Clark, Charles; Edwards, Mark

2016-05-01

A recent NIST experiment studied the transport of a gaseous Bose-Einstein condensate (BEC) confined in an atomtronic ``dumbbell'' circuit. The optically created condensate potential consisted of a tight harmonic potential in the vertical direction confining the BEC to a horizontial plane. The horizontal potential consisted of two cylindrical wells separated by a channel produced by a harmonic oscillator potential transverse to the line joining the wells. The BEC, formed in the ``source'' well, was released to flow toward the ``drain'' well. We modeled this system with the Gross-Pitaevskii (GP) equation and found good agreement with the data provided that the channel potential is carefully reproduced. The GP simulations show behavior, not detectable in the experiment, that atoms can jump out of the dumbbell area after filling up the drain well. We describe the GP evolution of this system with a model RCL circuit having a time-dependent resistance. This resistance exhibits a strong connection to the time-dependence of the atom loss in the drain. We also studied and present the dependence of the R and L parameters of this model circuit on the channel shape. Supported by NSF Grant PHY-1413768 and ARO Atomtronics MURI.

Ghost imaging with atoms

NASA Astrophysics Data System (ADS)

Khakimov, R. I.; Henson, B. M.; Shin, D. K.; Hodgman, S. S.; Dall, R. G.; Baldwin, K. G. H.; Truscott, A. G.

2016-12-01

Ghost imaging is a counter-intuitive phenomenon—first realized in quantum optics—that enables the image of a two-dimensional object (mask) to be reconstructed using the spatio-temporal properties of a beam of particles with which it never interacts. Typically, two beams of correlated photons are used: one passes through the mask to a single-pixel (bucket) detector while the spatial profile of the other is measured by a high-resolution (multi-pixel) detector. The second beam never interacts with the mask. Neither detector can reconstruct the mask independently, but temporal cross-correlation between the two beams can be used to recover a ‘ghost’ image. Here we report the realization of ghost imaging using massive particles instead of photons. In our experiment, the two beams are formed by correlated pairs of ultracold, metastable helium atoms, which originate from s-wave scattering of two colliding Bose-Einstein condensates. We use higher-order Kapitza-Dirac scattering to generate a large number of correlated atom pairs, enabling the creation of a clear ghost image with submillimetre resolution. Future extensions of our technique could lead to the realization of ghost interference, and enable tests of Einstein-Podolsky-Rosen entanglement and Bell’s inequalities with atoms.

Parametric Instability Rates in Periodically Driven Band Systems

NASA Astrophysics Data System (ADS)

Lellouch, S.; Bukov, M.; Demler, E.; Goldman, N.

2017-04-01

In this work, we analyze the dynamical properties of periodically driven band models. Focusing on the case of Bose-Einstein condensates, and using a mean-field approach to treat interparticle collisions, we identify the origin of dynamical instabilities arising from the interplay between the external drive and interactions. We present a widely applicable generic numerical method to extract instability rates and link parametric instabilities to uncontrolled energy absorption at short times. Based on the existence of parametric resonances, we then develop an analytical approach within Bogoliubov theory, which quantitatively captures the instability rates of the system and provides an intuitive picture of the relevant physical processes, including an understanding of how transverse modes affect the formation of parametric instabilities. Importantly, our calculations demonstrate an agreement between the instability rates determined from numerical simulations and those predicted by theory. To determine the validity regime of the mean-field analysis, we compare the latter to the weakly coupled conserving approximation. The tools developed and the results obtained in this work are directly relevant to present-day ultracold-atom experiments based on shaken optical lattices and are expected to provide an insightful guidance in the quest for Floquet engineering.

Periodic driving control of Raman-induced spin-orbit coupling in Bose-Einstein condensates: The heating mechanisms

NASA Astrophysics Data System (ADS)

Gomez Llorente, J. M.; Plata, J.

2016-06-01

We focus on a technique recently implemented for controlling the magnitude of synthetic spin-orbit coupling (SOC) in ultracold atoms in the Raman-coupling scenario. This technique uses a periodic modulation of the Raman-coupling amplitude to tune the SOC. Specifically, it has been shown that the effect of a high-frequency sinusoidal modulation of the Raman-laser intensity can be incorporated into the undriven Hamiltonian via effective parameters, whose adiabatic variation can therefore be used to tune the SOC. Here, we characterize the heating mechanisms that can be relevant to this method. We identify the main mechanism responsible for the heating observed in the experiments as basically rooted in driving-induced transfer of population to excited states. Characteristics of that process determined by the harmonic trapping, the decay of the excited states, and the technique used for preparing the system are discussed. Additional heating, rooted in departures from adiabaticity in the variation of the effective parameters, is also described. Our analytical study provides some clues that may be useful in the design of strategies for curbing the effects of heating on the efficiency of the control methods.

Proton cooling in ultracold low-density electron gas

NASA Astrophysics Data System (ADS)

Bobrov, A. A.; Bronin, S. Y.; Manykin, E. A.; Zelener, B. B.; Zelener, B. V.; Khikhlukha, D. R.

2015-11-01

A sole proton energy loss processes in an electron gas and the dependence of these processes on temperature and magnetic field are studied using molecular dynamics techniques in present work. It appears that for electron temperatures less than 100 K many body collisions affect the proton energy loss and these collisions must be taken into account. The influence of a strong magnetic field on the relaxation processes is also considered in this work. Calculations were performed for electron densities 10 cm-3, magnetic field 1-3 Tesla, electron temperatures 10-50 K, initial proton energies 100-10000 K.

Self-bound droplets of a dilute magnetic quantum liquid

NASA Astrophysics Data System (ADS)

Schmitt, Matthias; Wenzel, Matthias; Böttcher, Fabian; Ferrier-Barbut, Igor; Pfau, Tilman

2016-11-01

Self-bound many-body systems are formed through a balance of attractive and repulsive forces and occur in many physical scenarios. Liquid droplets are an example of a self-bound system, formed by a balance of the mutual attractive and repulsive forces that derive from different components of the inter-particle potential. It has been suggested that self-bound ensembles of ultracold atoms should exist for atom number densities that are 108 times lower than in a helium droplet, which is formed from a dense quantum liquid. However, such ensembles have been elusive up to now because they require forces other than the usual zero-range contact interaction, which is either attractive or repulsive but never both. On the basis of the recent finding that an unstable bosonic dipolar gas can be stabilized by a repulsive many-body term, it was predicted that three-dimensional self-bound quantum droplets of magnetic atoms should exist. Here we report the observation of such droplets in a trap-free levitation field. We find that this dilute magnetic quantum liquid requires a minimum, critical number of atoms, below which the liquid evaporates into an expanding gas as a result of the quantum pressure of the individual constituents. Consequently, around this critical atom number we observe an interaction-driven phase transition between a gas and a self-bound liquid in the quantum degenerate regime with ultracold atoms. These droplets are the dilute counterpart of strongly correlated self-bound systems such as atomic nuclei and helium droplets.

Self-bound droplets of a dilute magnetic quantum liquid.

PubMed

Schmitt, Matthias; Wenzel, Matthias; Böttcher, Fabian; Ferrier-Barbut, Igor; Pfau, Tilman

2016-11-10

Self-bound many-body systems are formed through a balance of attractive and repulsive forces and occur in many physical scenarios. Liquid droplets are an example of a self-bound system, formed by a balance of the mutual attractive and repulsive forces that derive from different components of the inter-particle potential. It has been suggested that self-bound ensembles of ultracold atoms should exist for atom number densities that are 10 8 times lower than in a helium droplet, which is formed from a dense quantum liquid. However, such ensembles have been elusive up to now because they require forces other than the usual zero-range contact interaction, which is either attractive or repulsive but never both. On the basis of the recent finding that an unstable bosonic dipolar gas can be stabilized by a repulsive many-body term, it was predicted that three-dimensional self-bound quantum droplets of magnetic atoms should exist. Here we report the observation of such droplets in a trap-free levitation field. We find that this dilute magnetic quantum liquid requires a minimum, critical number of atoms, below which the liquid evaporates into an expanding gas as a result of the quantum pressure of the individual constituents. Consequently, around this critical atom number we observe an interaction-driven phase transition between a gas and a self-bound liquid in the quantum degenerate regime with ultracold atoms. These droplets are the dilute counterpart of strongly correlated self-bound systems such as atomic nuclei and helium droplets.

Shear viscosity in an anisotropic unitary Fermi gas

NASA Astrophysics Data System (ADS)

Samanta, Rickmoy; Sharma, Rishi; Trivedi, Sandip P.

2017-11-01

We consider a system consisting of a strongly interacting, ultracold unitary Fermi gas under harmonic confinement. Our analysis suggests the possibility of experimentally studying, in this system, an anisotropic shear viscosity tensor driven by the anisotropy in the trapping potential. In particular, we suggest that this experimental setup could mimic some features of anisotropic geometries that have recently been studied for strongly coupled field theories which have a dual gravitational description. Results using the AdS/CFT (anti-de Sitter/conformal field theory correspondence) in these theories show that in systems with a background linear potential, certain viscosity components can be made much smaller than the entropy density, parametrically violating the bound proposed by Kovtun, Son, and Starinets (KSS). This intuition, along with results from a Boltzmann analysis that we perform, suggests that a violation of the KSS bound can perhaps occur in the unitary Fermi gas system when it is subjected to a suitable anisotropic trapping potential which may be approximated to be linear in a suitable range of parameters. We give a concrete proposal for an experimental setup where an anisotropic shear viscosity tensor may arise. In such situations, it may also be possible to observe a reduction in the spin-1 component of the shear viscosity from its lowest value observed so far in ultracold Fermi gases. In extreme anisotropic situations, the reduction may be enough to reduce the shear viscosity to entropy ratio below the proposed KSS bound, although this regime is difficult to analyze in a theoretically controlled manner.

75 FR 9201 - Kilarc-Cow Creek Hydroelectric Project; Notice of Intention To Prepare an Environmental Impact...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-03-01

... March 13, 2009 application, Pacific Gas and Electric Company (licensee) proposes to surrender the...) electric generators, turbines and other equipment would be removed; (5) both forebays would be graded and... coordinator, CarLisa Linton at (202) 502-8416 or [email protected] . Kimberly D. Bose, Secretary...

Statistical properties and condensate fluctuation of attractive Bose gas with finite number of particles

NASA Astrophysics Data System (ADS)

Bera, Sangita; Lekala, Mantile Leslie; Chakrabarti, Barnali; Bhattacharyya, Satadal; Rampho, Gaotsiwe Joel

2017-09-01

'We study the condensate fluctuation and several statistics of weakly interacting attractive Bose gas of 7 Li atoms in harmonic trap. Using exact recursion relation we calculate canonical ensemble partition function and study the thermal evolution of the condensate. As 7 Li condensate is associated with collapse, the number of condensate atom is truly finite and it facilitates to study the condensate in mesoscopic region. Being highly correlated, we utilize the two-body correlated basis function to get the many-body effective potential which is further used to calculate the energy levels. Taking van der Waals interaction as interatomic interaction we calculate several quantities like condensate fraction N, root-mean-square fluctuation δn0 and different orders of central moments. We observe the effect of finite size on the calculation of condensate fluctuations and the effect of attractive interaction over the noninteracting limit. We observe the depletion of the condensate with increase in temperature. The calculated moments nicely exhibit the mesoscopic effect. The sharp fall in the root-mean-square fluctuation near the critical point signifies the possibility of phase transition.

Storage rings for spin-polarized hydrogen

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thompson, D.; Lovelace, R.V.E.; Lee, D.

1989-11-01

A strong-focusing storage ring is proposed for the long-term magnetic confinement of a collisional gas of neutral spin-polarized hydrogen atoms in the Za{l arrow} and Zb{l arrow} hyperfine states. The trap uses the interaction of the magnetic moments of the gas atoms with a static magnetic field. Laser cooling and evaporative cooling can be utilized to enhance the confinement and to offset the influence of viscous heating. An important application of the trap is to the attainment of Bose--Einstein condensation.

Low temperatures shear viscosity of a two-component dipolar Fermi gas with unequal population

NASA Astrophysics Data System (ADS)

Darsheshdar, E.; Yavari, H.; Zangeneh, Z.

2016-07-01

By using the Green's functions method and linear response theory we calculate the shear viscosity of a two-component dipolar Fermi gas with population imbalance (spin polarized) in the low temperatures limit. In the strong-coupling Bose-Einstein condensation (BEC) region where a Feshbach resonance gives rise to tightly bound dimer molecules, a spin-polarized Fermi superfluid reduces to a simple Bose-Fermi mixture of Bose-condensed dimers and the leftover unpaired fermions (atoms). The interactions between dimer-atom, dimer-dimer, and atom-atom take into account to the viscous relaxation time (τη) . By evaluating the self-energies in the ladder approximation we determine the relaxation times due to dimer-atom (τDA) , dimer-dimer (τcDD ,τdDD) , and atom-atom (τAA) interactions. We will show that relaxation rates due to these interactions τDA-1 ,τcDD-1, τdDD-1, and τAA-1 have T2, T4, e - E /kB T (E is the spectrum of the dimer atoms), and T 3 / 2 behavior respectively in the low temperature limit (T → 0) and consequently, the atom-atom interaction plays the dominant role in the shear viscosity in this rang of temperatures. For small polarization (τDA ,τAA ≫τcDD ,τdDD), the low temperatures shear viscosity is determined by contact interaction between dimers and the shear viscosity varies as T-5 which has the same behavior as the viscosity of other superfluid systems such as superfluid neutron stars, and liquid helium.

Reaching Higher Gamma in Ultracold Neutral Plasmas Through Disorder-Induced Heating Control

DTIC Science & Technology

2016-06-27

shielding ,” Phys. Rev. E 87, 033101 (2013) 4 Sequential ionization of ultracold plasma ions A simulation published in 2007 by Michael Murillo showed...AFRL-AFOSR-VA-TR-2017-0031 Reaching higher Gamma in ultracold neutral plasmas through disorder-induced heating control Scott Bergeson BRIGHAM YOUNG...TYPE Final Report 3. DATES COVERED (From - To) 01 June 2012 - 31 May 2016 4. TITLE AND SUBTITLE Reaching higher Gamma in ultracold neutral plasmas

Critical behavior of a chiral superfluid in a bipartite square lattice

NASA Astrophysics Data System (ADS)

Okamoto, Junichi; Huang, Wen-Min; Höppner, Robert; Mathey, Ludwig

2018-01-01

We study the critical behavior of Bose-Einstein condensation in the second band of a bipartite optical square lattice in a renormalization group framework at one-loop order. Within our field theoretical representation of the system, we approximate the system as a two-component Bose gas in three dimensions. We demonstrate that the system is in a different universality class than the previously studied condensation in a frustrated triangular lattice due to an additional Umklapp scattering term, which stabilizes the chiral superfluid order at low temperatures. We derive the renormalization group flow of the system and show that this order persists in the low energy limit. Furthermore, the renormalization flow suggests that the phase transition from the thermal phase to the chiral superfluid state is first order.

Quantum noise in a transversely-pumped-cavity Bose-Hubbard model

NASA Astrophysics Data System (ADS)

Nagy, Dávid; Kónya, Gábor; Domokos, Peter; Szirmai, Gergely

2018-06-01

We investigate the quantum measurement noise effects on the dynamics of an atomic Bose lattice gas inside an optical resonator. We describe the dynamics by means of a hybrid model consisting of a Bose-Hubbard Hamiltonian for the atoms and a Heisenberg-Langevin equation for the lossy cavity-field mode. We assume that the atoms are prepared initially in the ground state of the lattice Hamiltonian and then start to interact with the cavity mode. We show that the cavity-field fluctuations originating from the dissipative outcoupling of photons from the resonator lead to vastly different effects in the different possible ground-state phases, i.e., the superfluid, the supersolid, the Mott and charge-density-wave phases. In the former two phases with the presence of a superfluid wavefunction, the quantum measurement noise appears as a driving term leading to depletion of the ground state. The timescale for the system to leave the ground state is presented in a simple analytical form. For the latter two incompressible phases, the quantum noise results in the fluctuation of the chemical potential. We derive an analytical expression for the corresponding broadening of the quasiparticle resonances.

Quantum bright solitons in a quasi-one-dimensional optical lattice

NASA Astrophysics Data System (ADS)

Barbiero, Luca; Salasnich, Luca

2014-06-01

We study a quasi-one-dimensional attractive Bose gas confined in an optical lattice with a superimposed harmonic potential by analyzing the one-dimensional Bose-Hubbard Hamiltonian of the system. Starting from the three-dimensional many-body quantum Hamiltonian, we derive strong inequalities involving the transverse degrees of freedom under which the one-dimensional Bose-Hubbard Hamiltonian can be safely used. To have a reliable description of the one-dimensional ground state, which we call a quantum bright soliton, we use the density-matrix-renormalization-group (DMRG) technique. By comparing DMRG results with mean-field (MF) ones, we find that beyond-mean-field effects become relevant by increasing the attraction between bosons or by decreasing the frequency of the harmonic confinement. In particular, we find that, contrary to the MF predictions based on the discrete nonlinear Schrödinger equation, average density profiles of quantum bright solitons are not shape-invariant. We also use the time-evolving-block-decimation method to investigate the dynamical properties of bright solitons when the frequency of the harmonic potential is suddenly increased. This quantum quench induces a breathing mode whose period crucially depends on the final strength of the superimposed harmonic confinement.

Effects of impurity and Bose-Fermi interactions on the transition temperature of a dilute dipolar Bose-Einstein condensation in trapped Bose-Fermi mixtures

NASA Astrophysics Data System (ADS)

Yavari, H.; Mokhtari, M.

2014-03-01

The effects of impurity and Bose-Fermi interactions on the transition temperature of a dipolar Bose-Einstein condensation in trapped Bose-Fermi mixture, by using the two-fluid model, are investigated. The shift of the transition temperature consists of four contributions due to contact, Bose-Fermi, dipole-dipole, and impurity interactions. We will show that in the presence of an anisotropic trap, the Bose-Fermi correction to the shift of transition temperature due to the excitation spectra of the thermal part is independent of anisotropy factor. Applying our results to trapped Bose-Fermi mixtures shows that, by knowing the impurity effect, the shift of the transition temperature due to Bose-Fermi interaction could be measured for isotropic trap (dipole-dipole contributions is zero) and Feshbach resonance technique (contact potential contribution is negligible).

Spin-Orbit Interactions and Quantum Spin Dynamics in Cold Ion-Atom Collisions

NASA Astrophysics Data System (ADS)

Tscherbul, Timur V.; Brumer, Paul; Buchachenko, Alexei A.

2016-09-01

We present accurate ab initio and quantum scattering calculations on a prototypical hybrid ion-atom system Yb+ -Rb, recently suggested as a promising candidate for the experimental study of open quantum systems, quantum information processing, and quantum simulation. We identify the second-order spin-orbit (SO) interaction as the dominant source of hyperfine relaxation in cold Yb+ -Rb collisions. Our results are in good agreement with recent experimental observations [L. Ratschbacher et al., Phys. Rev. Lett. 110, 160402 (2013)] of hyperfine relaxation rates of trapped Yb+ immersed in an ultracold Rb gas. The calculated rates are 4 times smaller than is predicted by the Langevin capture theory and display a weak T-0.3 temperature dependence, indicating significant deviations from statistical behavior. Our analysis underscores the deleterious nature of the SO interaction and implies that light ion-atom combinations such as Yb+ -Li should be used to minimize hyperfine relaxation and decoherence of trapped ions in ultracold atomic gases.

Observation of two-orbital spin-exchange interactions with ultracold SU(N)-symmetric fermions

NASA Astrophysics Data System (ADS)

Scazza, F.; Hofrichter, C.; Höfer, M.; de Groot, P. C.; Bloch, I.; Fölling, S.

2014-10-01

Spin-exchanging interactions govern the properties of strongly correlated electron systems such as many magnetic materials. When orbital degrees of freedom are present, spin exchange between different orbitals often dominates, leading to the Kondo effect, heavy fermion behaviour or magnetic ordering. Ultracold ytterbium or alkaline-earth ensembles have attracted much recent interest as model systems for these effects, with two (meta-) stable electronic configurations representing independent orbitals. We report the observation of spin-exchanging contact interactions in a two-orbital SU(N)-symmetric quantum gas realized with fermionic 173Yb. We find strong inter-orbital spin exchange by spectroscopic characterization of all interaction channels and demonstrate SU(N = 6) symmetry within our measurement precision. The spin-exchange process is also directly observed through the dynamic equilibration of spin imbalances between ensembles in separate orbitals. The realization of an SU(N)-symmetric two-orbital Hubbard Hamiltonian opens the route to quantum simulations with extended symmetries and with orbital magnetic interactions, such as the Kondo lattice model.

Modeling Strongly Correlated Fermi Systems Using Ultra-Cold Atoms

DTIC Science & Technology

2008-06-28

the two-dimensional Hubbard model on a square lattice ( a model which is purported to describe the high-temperature superconducting cuprates...beams and (2) stroboscopically alternating the beams very rapidly (~100 kHz) such that the beams were never on simultaneously ( the atoms experience a ...gases relies on (1) using a large-volume, magnetic trap to compress the atomic gas to a volume that can be captured by an optical trap

Collisional Thermalization in Strongly Coupled Ultracold Neutral Plasmas

DTIC Science & Technology

2017-01-25

Beaumont, TX (4/16). “Studying Strongly Coupled Systems with Ultracold Plasmas," Department of Physics and Astronomy Colloquium, University of South...Alabama, Mobile, AL (11/15). “Collective Modes and Correlations in Strongly Coupled Ultracold Plasmas," Department of Physics and Astronomy

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS On control of kinematic parameters of ultracold neutrons in waveguides

NASA Astrophysics Data System (ADS)

Rivlin, Lev A.

2010-10-01

The possibility of controlling the kinematic parameters of ultracold neutrons (UCNs) is analysed by the example of a waveguide transfer and transformation of 2D images in ultracold neutrons and by the example of an increase in the concentration and deceleration/acceleration of ultracold neutrons during their transport in the waveguide with a variable cross section. The critical parameters of the problem are estimated, which indicates both consistency of the proposed approach and the emerging experimental limitations.

75 FR 55315 - Seminole Energy Services, LLC; Seminole Gas Company, LLC; Seminole High Plains, LLC; Lakeshore...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-09-10

... Investigations (DOI) as non- decisional staff in deliberations by the Commission in this docket. By this order... of Enforcement, Larry Parkinson, Director, DOI, and Geof Hobday of DOI to the January 15, 2009 list of staff excepted from the DOI non-decisional staff designation. Kimberly D. Bose, Secretary. [FR Doc...

76 FR 31326 - Gulf LNG Pipeline, LLC; Notice of Request Under Blanket Authorization

Federal Register 2010, 2011, 2012, 2013, 2014

2011-05-31

... the Commission's Regulations under the Natural Gas Act (NGA), as amended, for authority to construct... to section 157.205 of the regulations under the NGA (18 CFR 157.205), a protest to the request. If no... application for authorization pursuant to section 7 of the NGA. Dated: May 24, 2011. Kimberly D. Bose...

Repulsive atomic gas in a harmonic trap on the border of itinerant ferromagnetism.

PubMed

Conduit, G J; Simons, B D

2009-11-13

Alongside superfluidity, itinerant (Stoner) ferromagnetism remains one of the most well-characterized phases of correlated Fermi systems. A recent experiment has reported the first evidence for novel phase behavior on the repulsive side of the Feshbach resonance in a two-component ultracold Fermi gas. By adapting recent theoretical studies to the atomic trap geometry, we show that an adiabatic ferromagnetic transition would take place at a weaker interaction strength than is observed in experiment. This discrepancy motivates a simple nonequilibrium theory that takes account of the dynamics of magnetic defects and three-body losses. The formalism developed displays good quantitative agreement with experiment.

Single-Particle Properties of a Strongly Interacting Bose-Fermi Mixture Above the BEC Phase Transition Temperature

NASA Astrophysics Data System (ADS)

Kharga, D.; Inotani, D.; Hanai, R.; Ohashi, Y.

2017-06-01

We theoretically investigate the normal state properties of a Bose-Fermi mixture with a strong attractive interaction between Fermi and Bose atoms. We extend the ordinary T-matrix approximation (TMA) with respect to Bose-Fermi pairing fluctuations, to include the Hugenholtz-Pines' relation for all Bose Green's functions appearing in TMA self-energy diagrams. This extension is shown to be essentially important to correctly describe the physical properties of the Bose-Fermi mixture, especially near the Bose-Einstein condensation instability. Using this improved TMA, we clarify how the formation of composite fermions affects Bose and Fermi single-particle excitation spectra, over the entire interaction strength.

Superfluid Fermi atomic gas as a quantum simulator for the study of the neutron-star equation of state in the low-density region

NASA Astrophysics Data System (ADS)

van Wyk, Pieter; Tajima, Hiroyuki; Inotani, Daisuke; Ohnishi, Akira; Ohashi, Yoji

2018-01-01

We propose a theoretical idea to use an ultracold Fermi gas as a quantum simulator for the study of the low-density region of a neutron-star interior. Our idea is different from the standard quantum simulator that heads for perfect replication of another system, such as the Hubbard model discussed in high-Tc cuprates. Instead, we use the similarity between two systems and theoretically make up for the difference between them. That is, (1) we first show that the strong-coupling theory developed by Nozières and Schmitt-Rink (NSR) can quantitatively explain the recent experiment on the equation of state (EoS) in a 6Li superfluid Fermi gas in the BCS (Bardeen-Cooper-Schrieffer) unitary limit far below the superfluid phase-transition temperature Tc. This region is considered to be very similar to the low-density region (crust regime) of a neutron star (where a nearly unitary s -wave neutron superfluid is expected). (2) We then theoretically compensate the difference that, while the effective range reff is negligibly small in a superfluid 6Li Fermi gas, it cannot be ignored (reff=2.7 fm) in a neutron star, by extending the NSR theory to include effects of reff. The calculated EoS when reff=2.7 fm is shown to agree well with the previous neutron-star EoS in the low-density region predicted in nuclear physics. Our idea indicates that an ultracold atomic gas may more flexibly be used as a quantum simulator for the study of other complicated quantum many-body systems, when we use not only the experimental high tunability, but also the recent theoretical development in this field. Since it is difficult to directly observe a neutron-star interior, our idea would provide a useful approach to the exploration for this mysterious astronomical object.

Preemptive vortex-loop proliferation in multicomponent interacting Bose-Einstein condensates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dahl, E. K.; Kragset, S.; Sudboe, A.

2008-04-01

We use analytical arguments and large-scale Monte Carlo calculations to investigate the nature of the phase transitions between distinct complex superfluid phases in a two-component Bose-Einstein condensate when a nondissipative drag between the two components is being varied. We focus on understanding the role of topological defects in various phase transitions and develop vortex-matter arguments, allowing an analytical description of the phase diagram. We find the behavior of fluctuation induced vortex matter to be much more complex and substantially different from that of single-component superfluids. We propose and numerically investigate a drag-induced ''preemptive vortex loop proliferation'' scenario. Such a transitionmore » may be a quite generic feature in many multicomponent systems where symmetry is restored by a gas of several kinds of competing vortex loops.« less

Bose-Einstein condensation in chains with power-law hoppings: Exact mapping on the critical behavior in d-dimensional regular lattices.

PubMed

Dias, W S; Bertrand, D; Lyra, M L

2017-06-01

Recent experimental progress on the realization of quantum systems with highly controllable long-range interactions has impelled the study of quantum phase transitions in low-dimensional systems with power-law couplings. Long-range couplings mimic higher-dimensional effects in several physical contexts. Here, we provide the exact relation between the spectral dimension d at the band bottom and the exponent α that tunes the range of power-law hoppings of a one-dimensional ideal lattice Bose gas. We also develop a finite-size scaling analysis to obtain some relevant critical exponents and the critical temperature of the BEC transition. In particular, an irrelevant dangerous scaling field has to be taken into account when the hopping range is sufficiently large to make the effective dimensionality d>4.

Bose-Einstein condensation in chains with power-law hoppings: Exact mapping on the critical behavior in d -dimensional regular lattices

NASA Astrophysics Data System (ADS)

Dias, W. S.; Bertrand, D.; Lyra, M. L.

2017-06-01

Recent experimental progress on the realization of quantum systems with highly controllable long-range interactions has impelled the study of quantum phase transitions in low-dimensional systems with power-law couplings. Long-range couplings mimic higher-dimensional effects in several physical contexts. Here, we provide the exact relation between the spectral dimension d at the band bottom and the exponent α that tunes the range of power-law hoppings of a one-dimensional ideal lattice Bose gas. We also develop a finite-size scaling analysis to obtain some relevant critical exponents and the critical temperature of the BEC transition. In particular, an irrelevant dangerous scaling field has to be taken into account when the hopping range is sufficiently large to make the effective dimensionality d >4 .

Constraints on Bose-Einstein-condensed axion dark matter from the Hi nearby galaxy survey data

NASA Astrophysics Data System (ADS)

Li, Ming-Hua; Li, Zhi-Bing

2014-05-01

One of the leading candidates for dark matter is the axion or axionlike particle in the form of a Bose-Einstein condensate (BEC). In this paper, we present an analysis of 17 high-resolution galactic rotation curves from the Hi nearby galaxy survey (THINGS) data [F. Walter et al., Astron. J. 136, 2563 (2008)] in the context of the axionic Bose-Einstein condensed dark matter model. Assuming a repulsive two-body interaction, we solve the nonrelativistic Gross-Pitaevskii equation for N gravitationally trapped bosons in the Thomas-Fermi approximation. We obtain the maximum possible radius R and the mass profile M(r) of a dilute axionic Bose-Einstein condensed gas cloud. A standard least- χ2 method is employed to find the best-fit values of the total mass M of the axion BEC and its radius R. The local mass density of BEC axion dark matter is ρa ≃0.02 GeV /cm3, which agrees with that presented by Beck [C. Beck, Phys. Rev. Lett. 111, 231801 (2013)]. The axion mass ma we obtain depends not only on the best-fit value of R, but also on the s-wave scattering length a (ma∝a1/3). The transition temperature Ta of an axion BEC on galactic scales is also estimated. Comparing the calculated Ta with the ambient temperature of galaxies and galaxy clusters implies that a ˜10-3 fm. The corresponding axion mass is ma≃0.58 meV. We compare our results with others.

Application of Bogolyubov's theory of weakly nonideal Bose gases to the A+A, A+B, B+B reaction-diffusion system

NASA Astrophysics Data System (ADS)

Konkoli, Zoran

2004-01-01

Theoretical methods for dealing with diffusion-controlled reactions inevitably rely on some kind of approximation, and to find the one that works on a particular problem is not always easy. Here the approximation used by Bogolyubov to study a weakly nonideal Bose gas, referred to as the weakly nonideal Bose gas approximation (WBGA), is applied in the analysis of three reaction-diffusion models: (i) A+A→Ø, (ii) A+B→Ø, and (iii) A+A,B+B,A+B→Ø (the ABBA model). Two types of WBGA are considered, the simpler WBGA-I and the more complicated WBGA-II. All models are defined on the lattice to facilitate comparison with computer experiment (simulation). It is found that the WBGA describes the A+B reaction well, it reproduces the correct d/4 density decay exponent. However, it fails in the case of the A+A reaction and the ABBA model. (To cure the deficiency of WBGA in dealing with the A+A model, a hybrid of the WBGA and Kirkwood superposition approximations is suggested.) It is shown that the WBGA-I is identical to the dressed-tree calculation suggested by Lee [J. Phys. A 27, 2633 (1994)], and that the dressed-tree calculation does not lead to the d/2 density decay exponent when applied to the A+A reaction, as normally believed, but it predicts the d/4 decay exponent. Last, the usage of the small n0 approximation suggested by Mattis and Glasser [Rev. Mod. Phys. 70, 979 (1998)] is questioned if used beyond the A+B reaction-diffusion model.

Superfluidity and BCS-BEC crossover of ultracold atomic Fermi gases in mixed dimensions

NASA Astrophysics Data System (ADS)

Zhang, Leifeng; Chen, Qijin

Atomic Fermi gases have been under active investigation in the past decade. Here we study the superfluid and pairing phenomena of a two-component ultracold atomic Fermi gas in the presence of mixed dimensionality, in which one component is confined on a 1D optical lattice whereas the other is free in the 3D continuum. We assume a short-range pairing interaction and determine the superfluid transition temperature Tc and the phase diagram for the entire BCS-BEC crossover, using a pairing fluctuation theory which includes self-consistently the contributions of finite momentum pairs. We find that, as the lattice depth increases and the lattice spacing decreases, the behavior of Tc becomes very similar to that of a population imbalance Fermi gas in a simple 3D continuum. There is no superfluidity even at T = 0 below certain threshold of pairing strength in the BCS regime. Nonmonotonic Tc behavior and intermediate temperature superfluidity emerge, and for deep enough lattice, the Tc curve will split into two parts. Implications for experiment will be discussed. References: 1. Q.J. Chen, Ioan Kosztin, B. Janko, and K. Levin, Phys. Rev. B 59, 7083 (1999). 2. Chih-Chun Chien, Qijin Chen, Yan He, and K. Levin, Phys. Rev. Lett. 97, 090402(2006). Work supported by NSF of China and the National Basic Research Program of China.

Testing the Bose-Einstein Condensate dark matter model at galactic cluster scale

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harko, Tiberiu; Liang, Pengxiang; Liang, Shi-Dong

The possibility that dark matter may be in the form of a Bose-Einstein Condensate (BEC) has been extensively explored at galactic scale. In particular, good fits for the galactic rotations curves have been obtained, and upper limits for the dark matter particle mass and scattering length have been estimated. In the present paper we extend the investigation of the properties of the BEC dark matter to the galactic cluster scale, involving dark matter dominated astrophysical systems formed of thousands of galaxies each. By considering that one of the major components of a galactic cluster, the intra-cluster hot gas, is describedmore » by King's β-model, and that both intra-cluster gas and dark matter are in hydrostatic equilibrium, bound by the same total mass profile, we derive the mass and density profiles of the BEC dark matter. In our analysis we consider several theoretical models, corresponding to isothermal hot gas and zero temperature BEC dark matter, non-isothermal gas and zero temperature dark matter, and isothermal gas and finite temperature BEC, respectively. The properties of the finite temperature BEC dark matter cluster are investigated in detail numerically. We compare our theoretical results with the observational data of 106 galactic clusters. Using a least-squares fitting, as well as the observational results for the dark matter self-interaction cross section, we obtain some upper bounds for the mass and scattering length of the dark matter particle. Our results suggest that the mass of the dark matter particle is of the order of μ eV, while the scattering length has values in the range of 10{sup −7} fm.« less

Many-body excitations and deexcitations in trapped ultracold bosonic clouds

NASA Astrophysics Data System (ADS)

Theisen, Marcus; Streltsov, Alexej I.

2016-11-01

We employ the multiconfigurational time-dependent Hartree for bosons (MCTDHB) method to study excited states of interacting Bose-Einstein condensates confined by harmonic and double-well trap potentials. Two approaches to access excitations, one static and the other dynamic, are investigated and contrasted. In static simulations the low-lying excitations are computed by utilizing a linear-response theory constructed on top of a static MCTDHB solution (LR-MCTDHB). Complimentarily, we propose two dynamic protocols that address excitations by propagating the MCTDHB wave function. In particular, we investigate dipolelike oscillations induced by shifting the origin of the confining potential and breathinglike excitations by quenching the frequency of a parabolic part of the trap. To contrast static predictions and dynamic results we compute the time evolution and regard the respective Fourier transform of several local and nonlocal observables. Namely, we study the expectation value of the position operator , its variance Var [x (t )] , and a local density computed at selected positions. We find that the variance is the most sensitive and informative quantity: Along with excitations it contains information about deexcitations even in a linear regime of the induced dynamics. The dynamic protocols are found to access the many-body excitations predicted by the static LR-MCTDHB approach.

Focus on the Rashba effect

NASA Astrophysics Data System (ADS)

Bihlmayer, G.; Rader, O.; Winkler, R.

2015-05-01

The Rashba effect, discovered in 1959, continues to supply fertile ground for fundamental research and applications. It provided the basis for the proposal of the spin transistor by Datta and Das in 1990, which has largely inspired the broad and dynamic field of spintronics. More recent developments include new materials for the Rashba effect such as metal surfaces, interfaces and bulk materials. It has also given rise to new phenomena such as spin currents and the spin Hall effect, including its quantized version, which has led to the very active field of topological insulators. The Rashba effect plays a crucial role in yet more exotic fields of physics such as the search for Majorana fermions at semiconductor-superconductor interfaces and the interaction of ultracold atomic Bose and Fermi gases. Advances in our understanding of Rashba-type spin-orbit couplings, both qualitatively and quantitatively, can be obtained in many different ways. This focus issue brings together the wide range of research activities on Rashba physics to further promote the development of our physical pictures and concepts in this field. The present Editorial gives a brief account on the history of the Rashba effect including material that was previously not easily accessible before summarizing the key results of the present focus issue as a guidance to the reader.

Nonequilibrium steady states of ideal bosonic and fermionic quantum gases.

PubMed

Vorberg, Daniel; Wustmann, Waltraut; Schomerus, Henning; Ketzmerick, Roland; Eckardt, André

2015-12-01

We investigate nonequilibrium steady states of driven-dissipative ideal quantum gases of both bosons and fermions. We focus on systems of sharp particle number that are driven out of equilibrium either by the coupling to several heat baths of different temperature or by time-periodic driving in combination with the coupling to a heat bath. Within the framework of (Floquet-)Born-Markov theory, several analytical and numerical methods are described in detail. This includes a mean-field theory in terms of occupation numbers, an augmented mean-field theory taking into account also nontrivial two-particle correlations, and quantum-jump-type Monte Carlo simulations. For the case of the ideal Fermi gas, these methods are applied to simple lattice models and the possibility of achieving exotic states via bath engineering is pointed out. The largest part of this work is devoted to bosonic quantum gases and the phenomenon of Bose selection, a nonequilibrium generalization of Bose condensation, where multiple single-particle states are selected to acquire a large occupation [Phys. Rev. Lett. 111, 240405 (2013)]. In this context, among others, we provide a theory for transitions where the set of selected states changes, describe an efficient algorithm for finding the set of selected states, investigate beyond-mean-field effects, and identify the dominant mechanisms for heat transport in the Bose-selected state.

Localized Magnetic Moments with Tunable Spin Exchange in a Gas of Ultracold Fermions

NASA Astrophysics Data System (ADS)

Riegger, L.; Darkwah Oppong, N.; Höfer, M.; Fernandes, D. R.; Bloch, I.; Fölling, S.

2018-04-01

We report on the experimental realization of a state-dependent lattice for a two-orbital fermionic quantum gas with strong interorbital spin exchange. In our state-dependent lattice, the ground and metastable excited electronic states of 173Yb take the roles of itinerant and localized magnetic moments, respectively. Repulsive on-site interactions in conjunction with the tunnel mobility lead to spin exchange between mobile and localized particles, modeling the coupling term in the well-known Kondo Hamiltonian. In addition, we find that this exchange process can be tuned resonantly by varying the on-site confinement. We attribute this to a resonant coupling to center-of-mass excited bound states of one interorbital scattering channel.

Ultracold molecule assembly with photonic crystals

NASA Astrophysics Data System (ADS)

Pérez-Ríos, Jesús; Kim, May E.; Hung, Chen-Lung

2017-12-01

Photoassociation (PA) is a powerful technique to synthesize molecules directly and continuously from cold and ultracold atoms into deeply bound molecular states. In freespace, however, PA efficiency is constrained by the number of spontaneous decay channels linking the initial excited molecular state to a sea of final (meta)stable rovibronic levels. Here, we propose a novel scheme based on molecules strongly coupled to a guided photonic mode in a photonic crystal waveguide that turns PA into a powerful tool for near deterministic formation of ultracold molecules in their ground rovibrational level. Our example shows a potential ground state molecule production efficiency > 90 % , and a saturation rate > {10}6 molecules per second. By combining state-of-the-art cold atomic and molecular physics with nanophotonic engineering, our scheme presents a novel experimental package for trapping, cooling, and optically manipulating ultracold molecules, thus opening up new possibilities in the direction of ultracold chemistry and quantum information.

Universality of nonthermal behavior in spinor Bose condensates

NASA Astrophysics Data System (ADS)

Patil, Yogesh Sharad; Cheung, Hil F. H.; Shaffer, Airlia; Chen, Huiyao Y.; Vengalattore, Mukund

2016-05-01

Spinor Bose condensates exhibit a rich phase diagram with varied magnetic ordering and topological defects because of the close competition between their spin and charge dependent interactions. Quenching such a spinor condensate into a ferromagnetic state realizes robust non-equilibrium and prethermalized states whose macroscopic behavior differs from thermodynamic predictions. In previous work, we have identified the microscopic origin of prethermalization in Rubidium spinor gases as being the disparate energy scales of the phonon and magnon excitations in this gas. This identification of the microscopic origin enables us to broaden the scope of our studies to address fundamental questions regarding the equilibration of isolated quantum systems. We will discuss our recent results that suggest the universality of this coarsening behavior and evidence that this system can be mapped on to a non-thermal fixed point studied in high energy field theories. This work is supported by the ARO MURI on non-equilibrium dynamics.

Classical and quantum filaments in the ground state of trapped dipolar Bose gases

NASA Astrophysics Data System (ADS)

Cinti, Fabio; Boninsegni, Massimo

2017-07-01

We study, by quantum Monte Carlo simulations, the ground state of a harmonically confined dipolar Bose gas with aligned dipole moments and with the inclusion of a repulsive two-body potential of varying range. Two different limits can clearly be identified, namely, a classical one in which the attractive part of the dipolar interaction dominates and the system forms an ordered array of parallel filaments and a quantum-mechanical one, wherein filaments are destabilized by zero-point motion, and eventually the ground state becomes a uniform cloud. The physical character of the system smoothly evolves from classical to quantum mechanical as the range of the repulsive two-body potential increases. An intermediate regime is observed in which ordered filaments are still present, albeit forming different structures from the ones predicted classically; quantum-mechanical exchanges of indistinguishable particles across different filaments allow phase coherence to be established, underlying a global superfluid response.

Three-Component Soliton States in Spinor F =1 Bose-Einstein Condensates

NASA Astrophysics Data System (ADS)

Bersano, T. M.; Gokhroo, V.; Khamehchi, M. A.; D'Ambroise, J.; Frantzeskakis, D. J.; Engels, P.; Kevrekidis, P. G.

2018-02-01

Dilute-gas Bose-Einstein condensates are an exceptionally versatile test bed for the investigation of novel solitonic structures. While matter-wave solitons in one- and two-component systems have been the focus of intense research efforts, an extension to three components has never been attempted in experiments. Here, we experimentally demonstrate the existence of robust dark-bright-bright (DBB) and dark-dark-bright solitons in a multicomponent F =1 condensate. We observe lifetimes on the order of hundreds of milliseconds for these structures. Our theoretical analysis, based on a multiscale expansion method, shows that small-amplitude solitons of these types obey universal long-short wave resonant interaction models, namely, Yajima-Oikawa systems. Our experimental and analytical findings are corroborated by direct numerical simulations highlighting the persistence of, e.g., the DBB soliton states, as well as their robust oscillations in the trap.

Three-Component Soliton States in Spinor F=1 Bose-Einstein Condensates.

PubMed

Bersano, T M; Gokhroo, V; Khamehchi, M A; D'Ambroise, J; Frantzeskakis, D J; Engels, P; Kevrekidis, P G

2018-02-09

Dilute-gas Bose-Einstein condensates are an exceptionally versatile test bed for the investigation of novel solitonic structures. While matter-wave solitons in one- and two-component systems have been the focus of intense research efforts, an extension to three components has never been attempted in experiments. Here, we experimentally demonstrate the existence of robust dark-bright-bright (DBB) and dark-dark-bright solitons in a multicomponent F=1 condensate. We observe lifetimes on the order of hundreds of milliseconds for these structures. Our theoretical analysis, based on a multiscale expansion method, shows that small-amplitude solitons of these types obey universal long-short wave resonant interaction models, namely, Yajima-Oikawa systems. Our experimental and analytical findings are corroborated by direct numerical simulations highlighting the persistence of, e.g., the DBB soliton states, as well as their robust oscillations in the trap.

Higher first Chern numbers in one-dimensional Bose-Fermi mixtures

NASA Astrophysics Data System (ADS)

Knakkergaard Nielsen, Kristian; Wu, Zhigang; Bruun, G. M.

2018-02-01

We propose to use a one-dimensional system consisting of identical fermions in a periodically driven lattice immersed in a Bose gas, to realise topological superfluid phases with Chern numbers larger than 1. The bosons mediate an attractive induced interaction between the fermions, and we derive a simple formula to analyse the topological properties of the resulting pairing. When the coherence length of the bosons is large compared to the lattice spacing and there is a significant next-nearest neighbour hopping for the fermions, the system can realise a superfluid with Chern number ±2. We show that this phase is stable in a large region of the phase diagram as a function of the filling fraction of the fermions and the coherence length of the bosons. Cold atomic gases offer the possibility to realise the proposed system using well-known experimental techniques.

Bloch-Siegert shift in an interacting Bose-Einstein condensate

NASA Astrophysics Data System (ADS)

Zhang, Jinyi; Eigen, Christoph; Lopes, Raphael; Garratt, Sam; Rousso, David; Smith, Robert P.; Hadzibabic, Zoran; Navon, Nir

2017-04-01

The Bloch-Siegert shift (BSS) is a paradigmatic frequency shift that arises from the nonlinear response of a two-level system (TLS) subjected to strong driving fields. When a TLS is driven by a linearly polarized field, the co-rotating-wave component leads to the famous Rabi oscillations. By contrast the co-rotating-wave component, whose role is usually neglected in a weak driving, leads to a frequency shift of the TLS resonance frequency. This phenomenon is encountered in various areas, from quantum optics to nuclear magnetic resonance.Here, we investigate the BSS in a box-trapped 87 Rb Bose-Einstein condensate (BEC) driven by a strong oscillating magnetic field gradient. By tuning the chemical potential of the gas, we investigate how the BSS evolves from the ideal shift of the two lowest energy levels of a single particle in a box to the unexplored shift of long-wavelength collective excitations of the interacting BEC.

Superradiance-Driven Phonon Laser

NASA Astrophysics Data System (ADS)

Jiang, Ya-Jing; Lü, Hao; Jing, Hui

2018-04-01

We propose to enhance the generation of a phonon laser by exploiting optical superradiance. In our scheme, the optomechanical cavity contains a movable membrane, which supports a mechanical mode, and the superradiance cavity can generate the coherent collective light emissions by applying a transverse pump to an ultracold intracavity atomic gas. The superradiant emission turns out to be capable of enhancing the phonon laser performance. This indicates a new way to operate a phonon laser with the assistance of coherent atomic gases trapped in a cavity or lattice potentials.

Statefinder analysis of the superfluid Chaplygin gas model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Popov, V.A., E-mail: vladipopov@mail.ru

2011-10-01

The statefinder indices are employed to test the superfluid Chaplygin gas (SCG) model describing the dark sector of the universe. The model involves Bose-Einstein condensate (BEC) as dark energy (DE) and an excited state above it as dark matter (DM). The condensate is assumed to have a negative pressure and is embodied as an exotic fluid with the Chaplygin equation of state. Excitations forms the normal component of superfluid. The statefinder diagrams show the discrimination between the SCG scenario and other models with the Chaplygin gas and indicates a pronounced effect of the DM equation of state and an indirectmore » interaction between their two components on statefinder trajectories and a current statefinder location.« less

Statefinder analysis of the superfluid Chaplygin gas model

NASA Astrophysics Data System (ADS)

Popov, V. A.

2011-10-01

The statefinder indices are employed to test the superfluid Chaplygin gas (SCG) model describing the dark sector of the universe. The model involves Bose-Einstein condensate (BEC) as dark energy (DE) and an excited state above it as dark matter (DM). The condensate is assumed to have a negative pressure and is embodied as an exotic fluid with the Chaplygin equation of state. Excitations forms the normal component of superfluid. The statefinder diagrams show the discrimination between the SCG scenario and other models with the Chaplygin gas and indicates a pronounced effect of the DM equation of state and an indirect interaction between their two components on statefinder trajectories and a current statefinder location.

77 FR 66603 - Trunkline Gas Company, LLC; Notice of Intent To Prepare an Environmental Assessment for the...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-11-06

... hot taps on the Mainline pipeline, excavation and removal of two drip lines on Loopline 100-2, removal...) You can file a paper copy of your comments by mailing them to the following address: Kimberly D. Bose... comment. If you would prefer to receive a paper copy of the document instead of the CD version or would...

76 FR 4651 - Venice Gathering System, L.L.C.; Notice of Request Under Blanket Authorization

Federal Register 2010, 2011, 2012, 2013, 2014

2011-01-26

...) of the Commission's Regulations under the Natural Gas Act (NGA) as amended, to abandon in place an... intervene or notice of intervention and pursuant to Section 157.205 of the regulations under the NGA (18 CFR... to Section 7 of the NGA. Kimberly D. Bose, Secretary. [FR Doc. 2011-1568 Filed 1-25-11; 8:45 am...

Optical Lattice Simulations of Correlated Fermions

DTIC Science & Technology

2013-10-04

Zhang, Xiaopeng Li, W. Vincent Liu. Stripe , checkerboard, and liquid-crystal ordering from anisotropic p-orbital Fermi surfaces in optical lattices...Meeting "The Role of Interactions in Disorder Induced Damping of Dipole Oscillations of a Bose-Einstein Condensate", S. Pollack, APS March Meeting...Rev. A 85, 043603 (2012)], and also worked out the diffusive transport behavior of the polarized Fermi gas, including heat transport, spin Seebeck

Production, Manipulation, and Applications of Ultracold Polar Molecules

DTIC Science & Technology

2015-04-30

molecules, cooling, trapping, photoassociation, feshbach resonances, quantum simulation , ultracold collisions, ultracold chemistry, optical lattices...been a multitude of less predictable outcomes: special quantum information processing schemes, uses of entanglement such a spin-squeezing for better...field seeing states to high-field-seeking states (and back) at key points in the magnetic field. The molecules spontaneously emit photons as they are

Plasma oscillations in spherical Gaussian shaped ultracold neutral plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Tianxing; Lu, Ronghua, E-mail: lurh@siom.ac.cn; Guo, Li

2016-04-15

The collective plasma oscillations are investigated in ultracold neutral plasma with a non-uniform density profile. Instead of the plane configuration widely used, we derive the plasma oscillation equations with spherically symmetric distribution and Gaussian density profile. The damping of radial oscillation is found. The Tonks–Dattner resonances of the ultracold neutral plasma with an applied RF field are also calculated.

A hydrogen leak-tight, transparent cryogenic sample container for ultracold-neutron transmission measurements

NASA Astrophysics Data System (ADS)

Döge, Stefan; Hingerl, Jürgen

2018-03-01

The improvement of the number of extractable ultracold neutrons (UCNs) from converters based on solid deuterium (sD2) crystals requires a good understanding of the UCN transport and how the crystal's morphology influences its transparency to the UCNs. Measurements of the UCN transmission through cryogenic liquids and solids of interest, such as hydrogen (H2) and deuterium (D2), require sample containers with thin, highly polished and optically transparent windows and a well defined sample thickness. One of the most difficult sealing problems is that of light gases like hydrogen and helium at low temperatures against high vacuum. Here we report on the design of a sample container with two 1 mm thin amorphous silica windows cold-welded to aluminum clamps using indium wire gaskets, in order to form a simple, reusable, and hydrogen-tight cryogenic seal. The container meets the above-mentioned requirements and withstands up to 2 bar hydrogen gas pressure against isolation vacuum in the range of 10-5 to 10-7 mbar at temperatures down to 4.5 K. Additionally, photographs of the crystallization process are shown and discussed.

Quantum Simulation

NASA Astrophysics Data System (ADS)

Orzel, Chad

2017-06-01

One of the most active areas in atomic, molecular and optical physics is the use of ultracold atomic gases in optical lattices to simulate the behaviour of electrons in condensed matter systems. The larger mass, longer length scale, and tuneable interactions in these systems allow the dynamics of atoms moving in these systems to be followed in real time, and resonant light scattering by the atoms allows this motion to be probed on a microscopic scale using site-resolved imaging. This book reviews the physics of Hubbard-type models for both bosons and fermions in an optical lattice, which give rise to a rich variety of insulating and conducting phases depending on the lattice properties and interparticle interactions. It also discusses the effect of disorder on the transport of atoms in these models, and the recently discovered phenomenon of many-body localization. It presents several examples of experiments using both density and momentum imaging and quantum gas microscopy to study the motion of atoms in optical lattices. These illustrate the power and flexibility of ultracold-lattice analogues for exploring exotic states of matter at an unprecedented level of precision.

Exact dynamics of a one dimensional Bose gas in a periodic time-dependent harmonic trap

NASA Astrophysics Data System (ADS)

Scopa, Stefano; Unterberger, Jéremie; Karevski, Dragi

2018-05-01

We study the unitary dynamics of a 1D gas of hard-core bosons trapped into a harmonic potential which varies periodically in time with frequency . Such periodic systems can be classified into orbits of different monodromies corresponding to two different physical situations, namely the case in which the bosonic cloud remains stable during the time-evolution and the case where it turns out to be unstable. In the present work we derive in the large particle number limit exact results for the stroboscopic evolution of the energy and particle densities in both physical situations.

Ultracold Molecules in Optical Lattices: Efficient Production and Application to Molecular Clocks

DTIC Science & Technology

2015-05-03

near the intercombination- line threshold were measured for a variety of states, and explained by considering nonadiabatic effects ( Coriolis coupling) in...Moszynski, T. Zelevinsky. Nonadiabatic Effects in Ultracold Molecules via Anomalous Linear and Quadratic Zeeman Shifts, Physical Review Letters, (12...M. McDonald, G. Reinaudi, W. Skomorowski, R. Moszynski, T. Zelevinsky. Measurement of Nonadiabatic Effects in Ultracold Molecules via Anomalous

Editorial: Focus on Atom Optics and its Applications

NASA Astrophysics Data System (ADS)

Schmidt-Kaler, F.; Pfau, T.; Schmelcher, P.; Schleich, W.

2010-06-01

Atom optics employs the modern techniques of quantum optics and laser cooling to enable applications which often outperform current standard technologies. Atomic matter wave interferometers allow for ultra-precise sensors; metrology and clocks are pushed to an extraordinary accuracy of 17 digits using single atoms. Miniaturization and integration are driven forward for both atomic clocks and atom optical circuits. With the miniaturization of information-storage and -processing devices, the scale of single atoms is approached in solid state devices, where the laws of quantum physics lead to novel, advantageous features and functionalities. An upcoming branch of atom optics is the control of single atoms, potentially allowing solid state devices to be built atom by atom; some of which would be applicable in future quantum information processing devices. Selective manipulation of individual atoms also enables trace analysis of extremely rare isotopes. Additionally, sources of neutral atoms with high brightness are being developed and, if combined with photo ionization, even novel focused ion beam sources are within reach. Ultracold chemistry is fertilized by atomic techniques, when reactions of chemical constituents are investigated between ions, atoms, molecules, trapped or aligned in designed fields and cooled to ultra-low temperatures such that the reaction kinetics can be studied in a completely state-resolved manner. Focus on Atom Optics and its Applications Contents Sensitive gravity-gradiometry with atom interferometry: progress towards an improved determination of the gravitational constant F Sorrentino, Y-H Lien, G Rosi, L Cacciapuoti, M Prevedelli and G M Tino A single-atom detector integrated on an atom chip: fabrication, characterization and application D Heine, W Rohringer, D Fischer, M Wilzbach, T Raub, S Loziczky, XiYuan Liu, S Groth, B Hessmo and J Schmiedmayer Interaction of a propagating guided matter wave with a localized potential G L Gattobigio, A Couvert, B Georgeot and D Guéry-Odelin Analysis of the entanglement between two individual atoms using global Raman rotations A Gaëtan, C Evellin, J Wolters, P Grangier, T Wilk and A Browaeys Spin polarization transfer in ground and metastable helium atom collisions D Vrinceanu and H R Sadeghpour A fiber Fabry-Perot cavity with high finesse D Hunger, T Steinmetz, Y Colombe, C Deutsch, T W Hänsch and J Reichel Atomic wave packets in amplitude-modulated vertical optical lattices A Alberti, G Ferrari, V V Ivanov, M L Chiofalo and G M Tino Atom interferometry with trapped Bose-Einstein condensates: impact of atom-atom interactions Julian Grond, Ulrich Hohenester, Igor Mazets and Jörg Schmiedmayer Storage of protonated water clusters in a biplanar multipole rf trap C Greve, M Kröner, S Trippel, P Woias, R Wester and M Weidemüller Single-atom detection on a chip: from realization to application A Stibor, H Bender, S Kühnhold, J Fortágh, C Zimmermann and A Günther Ultracold atoms as a target: absolute scattering cross-section measurements P Würtz, T Gericke, A Vogler and H Ott Entanglement-assisted atomic clock beyond the projection noise limit Anne Louchet-Chauvet, Jürgen Appel, Jelmer J Renema, Daniel Oblak, Niels Kjaergaard and Eugene S Polzik Towards the realization of atom trap trace analysis for 39Ar J Welte, F Ritterbusch, I Steinke, M Henrich, W Aeschbach-Hertig and M K Oberthaler Resonant superfluidity in an optical lattice I Titvinidze, M Snoek and W Hofstetter Interference of interacting matter waves Mattias Gustavsson, Elmar Haller, Manfred J Mark, Johann G Danzl, Russell Hart, Andrew J Daley and Hanns-Christoph Nägerl Magnetic trapping of NH molecules with 20 s lifetimes E Tsikata, W C Campbell, M T Hummon, H-I Lu and J M Doyle Imprinting patterns of neutral atoms in an optical lattice using magnetic resonance techniques Michal Karski, Leonid Förster, Jai-Min Choi, Andreas Steffen, Noomen Belmechri, Wolfgang Alt, Dieter Meschede and Artur Widera Frequency stability of optical lattice clocks Jérôme Lodewyck, Philip G Westergaard, Arnaud Lecallier, Luca Lorini and Pierre Lemonde Ultracold quantum gases in triangular optical lattices C Becker, P Soltan-Panahi, J Kronjäger, S Dörscher, K Bongs and K Sengstock Cold atoms near superconductors: atomic spin coherence beyond the Johnson noise limit B Kasch, H Hattermann, D Cano, T E Judd, S Scheel, C Zimmermann, R Kleiner, D Koelle and J Fortágh Focusing a deterministic single-ion beam Wolfgang Schnitzler, Georg Jacob, Robert Fickler, Ferdinand Schmidt-Kaler and Kilian Singer Tuning the structural and dynamical properties of a dipolar Bose-Einstein condensate: ripples and instability islands M Asad-uz-Zaman and D Blume Double-resonance lineshapes in a cell with wall coating and buffer gas Svenja Knappe and Hugh G Robinson Transport and interaction blockade of cold bosonic atoms in a triple-well potential P Schlagheck, F Malet, J C Cremon and S M Reimann Fabrication of a planar micro Penning trap and numerical investigations of versatile ion positioning protocols M Hellwig, A Bautista-Salvador, K Singer, G Werth and F Schmidt-Kaler Laser cooling of a magnetically guided ultracold atom beam A Aghajani-Talesh, M Falkenau, V V Volchkov, L E Trafford, T Pfau and A Griesmaier Creation efficiency of nitrogen-vacancy centres in diamond S Pezzagna, B Naydenov, F Jelezko, J Wrachtrup and J Meijer Top-down pathways to devices with few and single atoms placed to high precision Jessica A Van Donkelaar, Andrew D Greentree, Andrew D C Alves, Lenneke M Jong, Lloyd C L Hollenberg and David N Jamieson Enhanced electric field sensitivity of rf-dressed Rydberg dark states M G Bason, M Tanasittikosol, A Sargsyan, A K Mohapatra, D Sarkisyan, R M Potvliege and C S Adams

Itinerant ferromagnetism in an interacting Fermi gas with mass imbalance

NASA Astrophysics Data System (ADS)

von Keyserlingk, C. W.; Conduit, G. J.

2011-05-01

We study the emergence of itinerant ferromagnetism in an ultracold atomic gas with a variable mass ratio between the up- and down-spin species. Mass imbalance breaks the SU(2) spin symmetry, leading to a modified Stoner criterion. We first elucidate the phase behavior in both the grand canonical and canonical ensembles. Second, we apply the formalism to a harmonic trap to demonstrate how a mass imbalance delivers unique experimental signatures of ferromagnetism. These could help future experiments to better identify the putative ferromagnetic state. Furthermore, we highlight how a mass imbalance suppresses the three-body loss processes that handicap the formation of a ferromagnetic state. Finally, we study the time-dependent formation of the ferromagnetic phase following a quench in the interaction strength.

Sympathetic cooling of polyatomic molecules with S-state atoms in a magnetic trap.

PubMed

Tscherbul, T V; Yu, H-G; Dalgarno, A

2011-02-18

We present a rigorous theoretical study of low-temperature collisions of polyatomic molecular radicals with (1)S(0) atoms in the presence of an external magnetic field. Accurate quantum scattering calculations based on ab initio and scaled interaction potentials show that collision-induced spin relaxation of the prototypical organic molecule CH(2)(X(3)B(1)) (methylene) and nine other triatomic radicals in cold (3)He gas occurs at a slow rate, demonstrating that cryogenic buffer-gas cooling and magnetic trapping of these molecules is feasible with current technology. Our calculations further suggest that it may be possible to create ultracold gases of polyatomic molecules by sympathetic cooling with alkaline-earth atoms in a magnetic trap.

Stepwise Bose-Einstein Condensation in a Spinor Gas.

PubMed

Frapolli, C; Zibold, T; Invernizzi, A; Jiménez-García, K; Dalibard, J; Gerbier, F

2017-08-04

We observe multistep condensation of sodium atoms with spin F=1, where the different Zeeman components m_{F}=0,±1 condense sequentially as the temperature decreases. The precise sequence changes drastically depending on the magnetization m_{z} and on the quadratic Zeeman energy q (QZE) in an applied magnetic field. For large QZE, the overall structure of the phase diagram is the same as for an ideal spin-1 gas, although the precise locations of the phase boundaries are significantly shifted by interactions. For small QZE, antiferromagnetic interactions qualitatively change the phase diagram with respect to the ideal case, leading, for instance, to condensation in m_{F}=±1, a phenomenon that cannot occur for an ideal gas with q>0.

Collective excitation frequencies and stationary states of trapped dipolar Bose-Einstein condensates in the Thomas-Fermi regime

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bijnen, R. M. W. van; Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1; Parker, N. G.

We present a general method for obtaining the exact static solutions and collective excitation frequencies of a trapped Bose-Einstein condensate (BEC) with dipolar atomic interactions in the Thomas-Fermi regime. The method incorporates analytic expressions for the dipolar potential of an arbitrary polynomial density profile, thereby reducing the problem of handling nonlocal dipolar interactions to the solution of algebraic equations. We comprehensively map out the static solutions and excitation modes, including non-cylindrically-symmetric traps, and also the case of negative scattering length where dipolar interactions stabilize an otherwise unstable condensate. The dynamical stability of the excitation modes gives insight into the onsetmore » of collapse of a dipolar BEC. We find that global collapse is consistently mediated by an anisotropic quadrupolar collective mode, although there are two trapping regimes in which the BEC is stable against quadrupole fluctuations even as the ratio of the dipolar to s-wave interactions becomes infinite. Motivated by the possibility of a fragmented condensate in a dipolar Bose gas due to the partially attractive interactions, we pay special attention to the scissors modes, which can provide a signature of superfluidity, and identify a long-range restoring force which is peculiar to dipolar systems. As part of the supporting material for this paper we provide the computer program used to make the calculations, including a graphical user interface.« less

Nonequilibrium steady states of ideal bosonic and fermionic quantum gases

NASA Astrophysics Data System (ADS)

Vorberg, Daniel; Wustmann, Waltraut; Schomerus, Henning; Ketzmerick, Roland; Eckardt, André

2015-12-01

We investigate nonequilibrium steady states of driven-dissipative ideal quantum gases of both bosons and fermions. We focus on systems of sharp particle number that are driven out of equilibrium either by the coupling to several heat baths of different temperature or by time-periodic driving in combination with the coupling to a heat bath. Within the framework of (Floquet-)Born-Markov theory, several analytical and numerical methods are described in detail. This includes a mean-field theory in terms of occupation numbers, an augmented mean-field theory taking into account also nontrivial two-particle correlations, and quantum-jump-type Monte Carlo simulations. For the case of the ideal Fermi gas, these methods are applied to simple lattice models and the possibility of achieving exotic states via bath engineering is pointed out. The largest part of this work is devoted to bosonic quantum gases and the phenomenon of Bose selection, a nonequilibrium generalization of Bose condensation, where multiple single-particle states are selected to acquire a large occupation [Phys. Rev. Lett. 111, 240405 (2013), 10.1103/PhysRevLett.111.240405]. In this context, among others, we provide a theory for transitions where the set of selected states changes, describe an efficient algorithm for finding the set of selected states, investigate beyond-mean-field effects, and identify the dominant mechanisms for heat transport in the Bose-selected state.

Understanding Molecular Ion-Neutral Atom Collisions for the Production of Ultracold Molecular Ions

DTIC Science & Technology

2016-06-06

Understanding Molecular Ion-Neutral Atom Collisions for the Production of Utracold Molecular Ions In the last five years, the study of ultracold...U.S. Army Research Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 molecular ion, quantum chemistry, atom ion interaction...Molecular Ion-Neutral Atom Collisions for the Production of Utracold Molecular Ions Report Title In the last five years, the study of ultracold molecular

Mode-Locked Deceleration of Molecular Beams: Physics with Ultracold Molecules

DTIC Science & Technology

2017-02-07

AFRL-AFOSR-VA-TR-2017-0035 Mode-Locked Deceleration of Molecular Beams: Physics with Ultracold Molecules Wesley Campbell UNIVERSITY OF CALIFORNIA...REPORT TYPE Final 3. DATES COVERED (From - To) April 2013 - June 2016 4. TITLE AND SUBTITLE Mode-Locked Deceleration of Molecular Beams: Physics with...of Molecular Beams: Physics with Ultracold Molecules" P.I. Wesley C. Campbell Report Period: April 1, 2013- March 30, 2016 As a direct result of

Effective Mass Calculations for Two-dimensional Gas of Dipolar Fermions

NASA Astrophysics Data System (ADS)

Seydi, I.; Abedinpour, S. H.; Tanatar, B.

2017-06-01

We consider a two-dimensional system of ultracold dipolar fermions with dipole moments aligned in the perpendicular direction. We use the static structure factor information from Fermi-Hypernetted-Chain calculations to obtain the effective many-body dipole-dipole interaction and calculate the many-body effective mass of the system within the G0W approximation to the self-energy. A large cancellation between different contributions to the self-energy results in a weak dependence of the effective mass on the interaction strength over a large range of coupling constants.

12th US-Japan Seminar: Many Body Quantum Systems from Quantum Gases to Metrology and Information Processing. Held in Madison, Wisconsin on 20-24 September 2015

DTIC Science & Technology

2016-06-03

Ultracold Atoms 5:10 Zelevinsky Ye Inouye High-precision spectroscopy with two-body quantum systems Low entropy quantum gas of polar molecules New limit...12th US-Japan Seminar: Many Body Quantum Systems from Quantum Gases to Metrology and Information Processing Support was provided for The 12th US...Japan Seminar on many body quantum systems which was held in Madison, Wisconsin from September 20 to 24, 2015 at the Monona Terrace Convention Center

Photoemission spectrum and effect of inhomogeneous pairing fluctuations in the BCS-BEC crossover regime of an ultracold Fermi gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsuchiya, Shunji; Ohashi, Yoji; CREST

2010-09-15

We investigate the photoemission-type spectrum in a cold Fermi gas which was recently measured by the JILA group [Stewart et al., Nature (London) 454, 744 (2008)]. This quantity gives us very useful information about single-particle properties in the BCS-BEC crossover. In this paper, including pairing fluctuations within a T-matrix theory, as well as effects of a harmonic trap within the local density approximation, we show that spatially inhomogeneous pairing fluctuations due to the trap potential are an important key to understanding the observed spectrum. In the crossover region, while strong pairing fluctuations lead to the so-called pseudogap phenomenon in themore » trap center, such strong-coupling effects are found to be weak around the edge of the gas. Our results including this effect are shown to agree well with the recent photoemission data of the JILA group.« less

Optoelectrical Cooling of Formaldehyde to Sub-Millikelvin Temperatures

NASA Astrophysics Data System (ADS)

Zeppenfeld, Martin

2016-05-01

Due to their strong long-range dipole-dipole interactions and large number of internal states, polar molecules cooled to ultracold temperatures enable fascinating applications ranging from ultracold chemistry to investigation of dipolar quantum gases. However, realizing a simple and general technique to cool molecules to ultracold temperatures, akin to laser cooling of atoms, has been a formidable challenge. We present results for opto-electrical Sisyphus cooling applied to formaldehyde (H2 CO). In this generally applicable cooling scheme, molecules repeatedly move up and down electric field gradients of a trapping potential in different rotational states to efficiently extract kinetic energy. A total of about 300,000 molecules are thereby cooled by a factor of 1000 to 400uK, resulting in a record-large ensemble of ultracold molecules. In addition to cooling of the motional degrees of freedom, optical pumping via a vibrational transition allows us to control the internal rotational state. We thereby achieve a purity of over 80% of formaldehyde molecules in a single rotational M-sublevel. Our experiment provides an excellent starting point for precision spectroscopy and investigation of ultracold collisions.

Coupling of a nanomechanical oscillator and an atomic three-level medium

NASA Astrophysics Data System (ADS)

Sanz-Mora, A.; Eisfeld, A.; Wüster, S.; Rost, J.-M.

2016-02-01

We theoretically investigate the coupling of an ultracold three-level atomic gas and a nanomechanical mirror via classical electromagnetic radiation. The radiation pressure on the mirror is modulated by absorption of a probe light field, caused by the atoms which are electromagnetically rendered nearly transparent, allowing the gas to affect the mirror. In turn, the mirror can affect the gas as its vibrations generate optomechanical sidebands in the control field. We show that the sidebands cause modulations of the probe intensity at the mirror frequency, which can be enhanced near atomic resonances. Through the radiation pressure from the probe beam onto the mirror, this results in resonant driving of the mirror. Controllable by the two-photon detuning, the phase relation of the driving to the mirror motion decides upon amplification or damping of mirror vibrations. This permits direct phase locking of laser amplitude modulations to the motion of a nanomechanical element opening a perspective for cavity-free cooling through coupling to an atomic gas.

Theory of a Nearly Two-Dimensional Dipolar Bose Gas

DTIC Science & Technology

2016-05-11

temperatures, and when roton excitations are present. Further, BECs in nearly 2D geometries take the form of quasi -condensates, or BECs with finite spatial...extent. Quasi -condensates behave like BECs on shorter length scales, but not on longer length scales. The project incorporates the presence of a quasi ... Quasi -Condensate 23 J. Superfluidity 25 III. Results 26 A. Three Dimensions with Contact Interactions 26 B. Two Dimensions with Contact Interactions

Optical Lattice Bose-Einstein Condensates and the dd Fusion - Iwamura Connection

NASA Astrophysics Data System (ADS)

Chubb, Talbot

2003-03-01

My conjecture: LENR dd fusion occurs in PdDx when a subset of the interstitial deuterons occupy tetrahedral sites in a PdDx crystallite. The tetrahedral deuterons(d's), which occupy shallow potential wells, behave as a superfluid, similar to ultracold Na atoms in shallow-well optical traps, as modeled by Jaksch et al.(D. Jaksch, et al, Phys. Rev. Lett., 81, 3108 (1998).) The tetrahedral d's form a deuteron (d) subsystem, which is neutralized by an electron subsystem containing an equal number of electrons. In the superfluid all the properties of each quasiparticle d are partitioned among N_s_i_te equivalent sites. The partitioning of the d point charge reduces the Coulomb self-repulsion within each quasiparticle pair, which causes wave function overlap at large N_s_i_t_e, allowing d-d fusion. Similarly, partitioning of the point charge of each single quasiparticle d reduces the Coulomb repulsion between it and an obstructing impurity atom, which causes wave function overlap between quasiparticle and atom at large N_s_i_t_e, allowing transmutation of the impurity atom. The Iwamura reaction(Y. Iwamura, et al, Japan J. of Appl. Physics, 41A, 4642 (2002).) is 4 ^2D^+_B_l_o_ch + 4 e^-_B_l_o_ch + ^1^3^3Cs arrow ^1^4^1Pr, with the reaction energy incoherently transferred to the lattice.

Floquet engineering of Haldane Chern insulators and chiral bosonic phase transitions

NASA Astrophysics Data System (ADS)

Plekhanov, Kirill; Roux, Guillaume; Le Hur, Karyn

2017-01-01

The realization of synthetic gauge fields has attracted a lot of attention recently in relation to periodically driven systems and the Floquet theory. In ultracold atom systems in optical lattices and photonic networks, this allows one to simulate exotic phases of matter such as quantum Hall phases, anomalous quantum Hall phases, and analogs of topological insulators. In this paper, we apply the Floquet theory to engineer anisotropic Haldane models on the honeycomb lattice and two-leg ladder systems. We show that these anisotropic Haldane models still possess a topologically nontrivial band structure associated with chiral edge modes. Focusing on (interacting) boson systems in s -wave bands of the lattice, we show how to engineer through the Floquet theory, a quantum phase transition (QPT) between a uniform superfluid and a Bose-Einstein condensate analog of Fulde-Ferrell-Larkin-Ovchinnikov states, where bosons condense at nonzero wave vectors. We perform a Ginzburg-Landau analysis of the QPT on the graphene lattice, and compute observables such as chiral currents and the momentum distribution. The results are supported by exact diagonalization calculations and compared with those of the isotropic situation. The validity of high-frequency expansion in the Floquet theory is also tested using time-dependent simulations for various parameters of the model. Last, we show that the anisotropic choice for the effective vector potential allows a bosonization approach in equivalent ladder (strip) geometries.

A three-layer magnetic shielding for the MAIUS-1 mission on a sounding rocket

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kubelka-Lange, André, E-mail: andre.kubelka@zarm.uni-bremen.de; Herrmann, Sven; Grosse, Jens

Bose-Einstein-Condensates (BECs) can be used as a very sensitive tool for experiments on fundamental questions in physics like testing the equivalence principle using matter wave interferometry. Since the sensitivity of these experiments in ground-based environments is limited by the available free fall time, the QUANTUS project started to perform BEC interferometry experiments in micro-gravity. After successful campaigns in the drop tower, the next step is a space-borne experiment. The MAIUS-mission will be an atom-optical experiment that will show the feasibility of experiments with ultra-cold quantum gases in microgravity in a sounding rocket. The experiment will create a BEC of 10{supmore » 5} {sup 87}Rb-atoms in less than 5 s and will demonstrate application of basic atom interferometer techniques over a flight time of 6 min. The hardware is specifically designed to match the requirements of a sounding rocket mission. Special attention is thereby spent on the appropriate magnetic shielding from varying magnetic fields during the rocket flight, since the experiment procedures are very sensitive to external magnetic fields. A three-layer magnetic shielding provides a high shielding effectiveness factor of at least 1000 for an undisturbed operation of the experiment. The design of this magnetic shielding, the magnetic properties, simulations, and tests of its suitability for a sounding rocket flight are presented in this article.« less

A three-layer magnetic shielding for the MAIUS-1 mission on a sounding rocket.

PubMed

Kubelka-Lange, André; Herrmann, Sven; Grosse, Jens; Lämmerzahl, Claus; Rasel, Ernst M; Braxmaier, Claus

2016-06-01

Bose-Einstein-Condensates (BECs) can be used as a very sensitive tool for experiments on fundamental questions in physics like testing the equivalence principle using matter wave interferometry. Since the sensitivity of these experiments in ground-based environments is limited by the available free fall time, the QUANTUS project started to perform BEC interferometry experiments in micro-gravity. After successful campaigns in the drop tower, the next step is a space-borne experiment. The MAIUS-mission will be an atom-optical experiment that will show the feasibility of experiments with ultra-cold quantum gases in microgravity in a sounding rocket. The experiment will create a BEC of 10(5) (87)Rb-atoms in less than 5 s and will demonstrate application of basic atom interferometer techniques over a flight time of 6 min. The hardware is specifically designed to match the requirements of a sounding rocket mission. Special attention is thereby spent on the appropriate magnetic shielding from varying magnetic fields during the rocket flight, since the experiment procedures are very sensitive to external magnetic fields. A three-layer magnetic shielding provides a high shielding effectiveness factor of at least 1000 for an undisturbed operation of the experiment. The design of this magnetic shielding, the magnetic properties, simulations, and tests of its suitability for a sounding rocket flight are presented in this article.

Ferroelectricity by Bose-Einstein condensation in a quantum magnet.

PubMed

Kimura, S; Kakihata, K; Sawada, Y; Watanabe, K; Matsumoto, M; Hagiwara, M; Tanaka, H

2016-09-26

The Bose-Einstein condensation is a fascinating phenomenon, which results from quantum statistics for identical particles with an integer spin. Surprising properties, such as superfluidity, vortex quantization or Josephson effect, appear owing to the macroscopic quantum coherence, which spontaneously develops in Bose-Einstein condensates. Realization of Bose-Einstein condensation is not restricted in fluids like liquid helium, a superconducting phase of paired electrons in a metal and laser-cooled dilute alkali atoms. Bosonic quasi-particles like exciton-polariton and magnon in solids-state systems can also undergo Bose-Einstein condensation in certain conditions. Here, we report that the quantum coherence in Bose-Einstein condensate of the magnon quasi particles yields spontaneous electric polarization in the quantum magnet TlCuCl 3 , leading to remarkable magnetoelectric effect. Very soft ferroelectricity is realized as a consequence of the O(2) symmetry breaking by magnon Bose-Einstein condensation. The finding of this ferroelectricity will open a new window to explore multi-functionality of quantum magnets.

Coherent Spectroscopy of Ultra-Cold Mercury for the UV to VUV

DTIC Science & Technology

2015-11-20

AFRL-AFOSR-VA-TR-2015-0388 COHERENT SPECTROSCOPY OF ULTRA-COLD MERCURY FOR THE UV TO VUV R Jason Jones ARIZONA UNIV BOARD OF REGENTS TUCSON Final...TITLE AND SUBTITLE COHERENT SPECTROSCOPY OF ULTRA-COLD MERCURY FOR THE UV TO VUV 5a. CONTRACT NUMBER 5b. GRANT NUMBER FA9550-09-1-0563 5c. PROGRAM...NUMBER(S) 12. DISTRIBUTION/AVAILABILITY STATEMENT Distribution A 13. SUPPLEMENTARY NOTES 14. ABSTRACT Narrow UV transitions in atomic Hg can be utilized

Probing and characterizing the growth of a crystal of ultracold bosons and light

NASA Astrophysics Data System (ADS)

Ostermann, S.; Piazza, F.; Ritsch, H.

2017-12-01

The non-linear coupled particle light dynamics of an ultracold gas in the field of two independent counter-propagating laser beams can lead to the dynamical formation of a self-ordered lattice structure as presented in (2016) Phys. Rev. X 6 021026. Here we present new numerical studies on experimentally observable signatures to monitor the growth and properties of such a crystal in real time. While, at least theoretically, optimal non-destructive observation of the growth dynamics and the hallmarks of the crystalline phase can be performed by analyzing scattered light, monitoring the evolution of the particle’s momentum distribution via time-of-flight probing is an experimentally more accessible choice. In this work we show that both approaches allow us to unambiguously distinguish the crystal from independent collective scattering as it occurs in matter wave super-radiance. As a clear crystallization signature, we identify spatial locking between the two emerging standing laser waves, together creating the crystal potential. For sufficiently large systems, the system allows reversible adiabatic ramping into the crystalline phase as an alternative to a quench across the phase transition and growth from fluctuations.

Equation of state of the one- and three-dimensional Bose-Bose gases

NASA Astrophysics Data System (ADS)

Chiquillo, Emerson

2018-06-01

We calculate the equation of state of Bose-Bose gases in one and three dimensions in the framework of an effective quantum field theory. The beyond-mean-field approximation at zero temperature and the one-loop finite-temperature results are obtained performing functional integration on a local effective action. The ultraviolet divergent zero-point quantum fluctuations are removed by means of dimensional regularization. We derive the nonlinear Schrödinger equation to describe one- and three-dimensional Bose-Bose mixtures and solve it analytically in the one-dimensional scenario. This equation supports self-trapped brightlike solitonic droplets and self-trapped darklike solitons. At low temperature, we also find that the pressure and the number of particles of symmetric quantum droplets have a nontrivial dependence on the chemical potential and the difference between the intra- and the interspecies coupling constants.

Superfluid-ferromagnet-superfluid junction and the {pi} phase in a superfluid Fermi gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kashimura, Takashi; Tsuchiya, Shunji; CREST

2010-09-15

We investigate the possibility of a superfluid-ferromagnet-superfluid (SFS) junction in a superfluid Fermi gas. To examine this possibility in a simple manner, we consider an attractive Hubbard model at T=0 within the mean-field theory. When a potential barrier is embedded in a superfluid Fermi gas with population imbalance (N{sub {up_arrow}}>N{sub {down_arrow}}, where N{sub {sigma}} is the number of atoms with pseudospin {sigma}= {up_arrow}, {down_arrow}), this barrier is shown to be magnetized in the sense that excess {up_arrow}-spin atoms are localized around it. The resulting superfluid Fermi gas is spatially divided into two by this ferromagnet, so that one obtains amore » junction similar to the superconductor-ferromagnet-superconductor junction discussed in superconductivity. Indeed, we show that the so-called {pi} phase, which is a typical phenomenon in the SFS junction, is realized, where the superfluid order parameter changes its sign across the junction. Our results would be useful for the study of magnetic effects on fermion superfluidity using an ultracold Fermi gas.« less

Ultrastable, Zerodur-based optical benches for quantum gas experiments.

PubMed

Duncker, Hannes; Hellmig, Ortwin; Wenzlawski, André; Grote, Alexander; Rafipoor, Amir Jones; Rafipoor, Mona; Sengstock, Klaus; Windpassinger, Patrick

2014-07-10

Operating ultracold quantum gas experiments outside of a laboratory environment has so far been a challenging goal, largely due to the lack of sufficiently stable optical systems. In order to increase the thermal stability of free-space laser systems, the application of nonstandard materials such as glass ceramics is required. Here, we report on Zerodur-based optical systems which include single-mode fiber couplers consisting of multiple components jointed by light-curing adhesives. The thermal stability is thoroughly investigated, revealing excellent fiber-coupling efficiencies between 0.85 and 0.92 in the temperature range from 17°C to 36°C. In conjunction with successfully performed vibration tests, these findings qualify our highly compact systems for atom interferometry experiments aboard a sounding rocket as well as various other quantum information and sensing applications.

Negative-Mass Instability of the Spin and Motion of an Atomic Gas Driven by Optical Cavity Backaction

NASA Astrophysics Data System (ADS)

Kohler, Jonathan; Gerber, Justin A.; Dowd, Emma; Stamper-Kurn, Dan M.

2018-01-01

We realize a spin-orbit interaction between the collective spin precession and center-of-mass motion of a trapped ultracold atomic gas, mediated by spin- and position-dependent dispersive coupling to a driven optical cavity. The collective spin, precessing near its highest-energy state in an applied magnetic field, can be approximated as a negative-mass harmonic oscillator. When the Larmor precession and mechanical motion are nearly resonant, cavity mediated coupling leads to a negative-mass instability, driving exponential growth of a correlated mode of the hybrid system. We observe this growth imprinted on modulations of the cavity field and estimate the full covariance of the resulting two-mode state by observing its transient decay during subsequent free evolution.

Itinerant ferromagnetism in an interacting Fermi gas with mass imbalance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Keyserlingk, C. W. von; Conduit, G. J.; Physics Department, Ben Gurion University, Beer Sheva 84105

2011-05-15

We study the emergence of itinerant ferromagnetism in an ultracold atomic gas with a variable mass ratio between the up- and down-spin species. Mass imbalance breaks the SU(2) spin symmetry, leading to a modified Stoner criterion. We first elucidate the phase behavior in both the grand canonical and canonical ensembles. Second, we apply the formalism to a harmonic trap to demonstrate how a mass imbalance delivers unique experimental signatures of ferromagnetism. These could help future experiments to better identify the putative ferromagnetic state. Furthermore, we highlight how a mass imbalance suppresses the three-body loss processes that handicap the formation ofmore » a ferromagnetic state. Finally, we study the time-dependent formation of the ferromagnetic phase following a quench in the interaction strength.« less

Cooper-pair and Bose-Einstein condensations in two dimensions: A critical analysis based on the Nozieres and Schmitt-Rink formalism

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tokumitu, A.; Miyake, K.; Yamada, K.

1993-05-01

The crossover between the Cooper-pair condensation and the Bose-Einstein condensation of di-electronic'' molecules in two-dimensional superconductors is investigated in detail on the basis of the Nozieres and Schmitt-Rink formalism. It is shown that temperature dependence of the chemical potential [mu] so calculated is classified into two classes as decreasing temperatures; i.e., class (a) where [mu] approaches the point of Bose-Einstein condensation of two-dimensional ideal Bose gas of di-electronic'' molecules, and class (b) where [mu] diverges positively along the line of BCS-type mean-field pair condensation. This feature is rather universal irrespective of strength [ital V] of the attractive interaction of themore » [ital s]-wave type. While the former class (a) has been found by Schmitt-Rink, Varma, and Ruckenstein, existence of the latter class (b) is recognized here. In the case where [ital V] is fixed, class (a) is realized for electron number density [ital N] smaller than [ital N][sub cr], which is an increasing function of [ital V], and class (b) is realized for [ital N] larger than [ital N][sub cr]. If [ital N][much gt][ital N][sub cr] in particular, there exists a regime, where the Fermi-liquid-like description is valid, between the BCS-type mean-field transition temperature and the Fermi temperature. In the situation where [ital V] is changed with [ital N] being fixed, low-temperature states for the strong-coupling case belong to class (a) while those for the weak-coupling case belong to class (b). Therefore, with decreasing [ital V], the chemical potential [mu]([ital T]), at temperatures far below the Fermi temperature, shows a discontinuous jump at [ital V]=[ital V][sub cr]([ital N]) corresponding to the transition from class (a) to (b).« less

Motion of a Distinguishable Impurity in the Bose Gas: Arrested Expansion Without a Lattice and Impurity Snaking

NASA Astrophysics Data System (ADS)

Robinson, Neil J.; Caux, Jean-Sébastien; Konik, Robert M.

2016-04-01

We consider the real-time dynamics of an initially localized distinguishable impurity injected into the ground state of the Lieb-Liniger model. Focusing on the case where integrability is preserved, we numerically compute the time evolution of the impurity density operator in regimes far from analytically tractable limits. We find that the injected impurity undergoes a stuttering motion as it moves and expands. For an initially stationary impurity, the interaction-driven formation of a quasibound state with a hole in the background gas leads to arrested expansion—a period of quasistationary behavior. When the impurity is injected with a finite center-of-mass momentum, the impurity moves through the background gas in a snaking manner, arising from a quantum Newton's cradlelike scenario where momentum is exchanged back and forth between the impurity and the background gas.

Motion of a distinguishable Impurity in the Bose gas: Arrested expansion without a lattice and impurity snaking

DOE PAGES

Neil J. Robinson; Caux, Jean -Sebastien; Konik, Robert M.

2016-04-07

We consider the real-time dynamics of an initially localized distinguishable impurity injected into the ground state of the Lieb-Liniger model. Focusing on the case where integrability is preserved, we numerically compute the time evolution of the impurity density operator in regimes far from analytically tractable limits. We find that the injected impurity undergoes a stuttering motion as it moves and expands. For an initially stationary impurity, the interaction-driven formation of a quasibound state with a hole in the background gas leads to arrested expansion—a period of quasistationary behavior. In conclusion, when the impurity is injected with a finite center-of-mass momentum,more » the impurity moves through the background gas in a snaking manner, arising from a quantum Newton’s cradlelike scenario where momentum is exchanged back and forth between the impurity and the background gas.« less

Photodissociation of ultracold diatomic strontium molecules with quantum state control.

PubMed

McDonald, M; McGuyer, B H; Apfelbeck, F; Lee, C-H; Majewska, I; Moszynski, R; Zelevinsky, T

2016-07-07

Chemical reactions at ultracold temperatures are expected to be dominated by quantum mechanical effects. Although progress towards ultracold chemistry has been made through atomic photoassociation, Feshbach resonances and bimolecular collisions, these approaches have been limited by imperfect quantum state selectivity. In particular, attaining complete control of the ground or excited continuum quantum states has remained a challenge. Here we achieve this control using photodissociation, an approach that encodes a wealth of information in the angular distribution of outgoing fragments. By photodissociating ultracold (88)Sr2 molecules with full control of the low-energy continuum, we access the quantum regime of ultracold chemistry, observing resonant and nonresonant barrier tunnelling, matter-wave interference of reaction products and forbidden reaction pathways. Our results illustrate the failure of the traditional quasiclassical model of photodissociation and instead are accurately described by a quantum mechanical model. The experimental ability to produce well-defined quantum continuum states at low energies will enable high-precision studies of long-range molecular potentials for which accurate quantum chemistry models are unavailable, and may serve as a source of entangled states and coherent matter waves for a wide range of experiments in quantum optics.

Bose-Einstein condensation in atomic alkali gases

NASA Astrophysics Data System (ADS)

Dodd, Robert J.

1998-05-01

I present a review of the time-independent Gross-Pitaevskii (GP), Bogoliubov, and finite-temperature Hartree-Fock-Bogoliubov (HFB) mean-field theories used to study trapped, Bose-Einstein condensed alkali gases. Numerical solutions of the (zero-temperature) GP equation are presented for attractive (negative scattering length) and repulsive (positive scattering length) interactions. Comparison is made with the Thomas-Fermi and (variational) trial wavefunction appr oximations that are used in the literature to study condensed gases. Numerical calculations of the (zero-temperature) Bogoliubov quasi-particle excitation frequencies are found to be in excellent agreement with the experimental results. The finite-temperature properties of condensed gases are examined using the Popov approximation (of the HFB theory) and a simple two-gas model. Specific, quantitative comparisons are made with experimental results for finite-temperature excitation frequencies. Qualitative comparisons are made between the results of the Popov approximation, two-gas model, and other published models for condensate fraction and thermal density distribution. The time-independent mean-field theories are found to be in excellent agreement with experimental results at relatively low temperatures (high condensate fractions). However, at higher temperatures (and condensate fractions of less than 50%) there are significant discrepancies between experimental data and theoretical calculations. This work was undertaken at the University of Maryland at College Park and was supported in part by the National Science Foundation (PHY-9601261) and the U.S. Office of Naval Research.

Laser Slowing of CaF Molecules and Progress towards a Dual-MOT for Li and CaF

NASA Astrophysics Data System (ADS)

Chae, Eunmi

Diatomic molecules are considered good candidates for the study of strongly correlated systems and precision measurement searches due to their combination of complex internal states and strong long-range interactions. Cooling molecules down to ultracold temperatures is often a necessary step for fully utilizing the power of the molecule. This requires a trap for molecules and the ability to cool molecules to the mK regime and below. A magneto-optical trap (MOT) is a good tool for achieving mK temperatures. However, extra care is needed for molecules to form the necessary quasi-closed cycling transitions due to molecule's complicated energy structure. In our work with CaF, we use two repump lasers to block vibrational leakage and selection rules for the rotational degree of freedom to achieve about 105 photon cycles. The two-stage buffer gas beam source is a general method to generate a cold and slow beam of molecules with a forward velocity of about 50 m/s. The compatibility of the buffer-gas source with a MOT is studied and we confirm that such beams can be nicely compatible with MOTs using various atomic species. In order to load molecules into a MOT from even such a slow beam, additional slowing is required due to the low capture velocity of a molecular MOT (< 10 m/s). We apply a frequency-broadened "white-light" slowing on CaF from a two-stage source, demonstrating slowing of CaF below 10 m/s. An AC MOT, which provides active remixing of dark substates, is also developed and Li atoms are slowed and trapped. These are crucial ingredients for co-trapping CaF molecules and Li atoms and study their collisional properties, which would lead to sympathetic cooling of molecules down to ultracold temperatures. The achievement of slowing and development of this system allowed for the detailed study of the CaF laser cooling system, as well as physical processes involved with AC MOTs and the proposed MOT for CaF. Crucial knowledge of this archetypal system provides significant progress toward manipulation and control of molecules similar to what has been achieved with atoms and what is necessary for searches for new physics with ultracold molecules.

Tunneling and traversal of ultracold three-level atoms through vacuum-induced potentials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Badshah, Fazal; Irfan, Muhammad; Qamar, Shahid

2011-09-15

The passage of ultracold three-level atoms through the potential induced by the vacuum cavity mode is discussed using cascade atomic configuration. We study the tunneling or traversal time of the ultracold atoms via a bimodal high-Q cavity. It is found that the phase time, which may be considered as a measure for the time required to traverse the cavity, exhibits superclassical and subclassical behaviors. Further, the dark states and interference effects in cascade atomic configuration may influence the passage time of the atom through the cavity.

Determination of the axial-vector weak coupling constant with ultracold neutrons.

PubMed

Liu, J; Mendenhall, M P; Holley, A T; Back, H O; Bowles, T J; Broussard, L J; Carr, R; Clayton, S; Currie, S; Filippone, B W; García, A; Geltenbort, P; Hickerson, K P; Hoagland, J; Hogan, G E; Hona, B; Ito, T M; Liu, C-Y; Makela, M; Mammei, R R; Martin, J W; Melconian, D; Morris, C L; Pattie, R W; Pérez Galván, A; Pitt, M L; Plaster, B; Ramsey, J C; Rios, R; Russell, R; Saunders, A; Seestrom, S J; Sondheim, W E; Tatar, E; Vogelaar, R B; VornDick, B; Wrede, C; Yan, H; Young, A R

2010-10-29

A precise measurement of the neutron decay β asymmetry A₀ has been carried out using polarized ultracold neutrons from the pulsed spallation ultracold neutron source at the Los Alamos Neutron Science Center. Combining data obtained in 2008 and 2009, we report A₀ = -0.119 66±0.000 89{-0.001 40}{+0.001 23}, from which we determine the ratio of the axial-vector to vector weak coupling of the nucleon g{A}/g{V}=-1.275 90{-0.004 45}{+0.004 09}.

Testing Lorentz and C P T invariance with ultracold neutrons

NASA Astrophysics Data System (ADS)

Martín-Ruiz, A.; Escobar, C. A.

2018-05-01

In this paper we investigate, within the standard model extension framework, the influence of Lorentz- and C P T -violating terms on gravitational quantum states of ultracold neutrons. Using a semiclassical wave packet, we derive the effective nonrelativistic Hamiltonian which describes the neutrons vertical motion by averaging the contributions from the perpendicular coordinates to the free falling axis. We compute the physical implications of the Lorentz- and C P T -violating terms on the spectra. The comparison of our results with those obtained in the GRANIT experiment leads to an upper bound for the symmetries-violation cμν n coefficients. We find that ultracold neutrons are sensitive to the ain and ein coefficients, which thus far are unbounded by experiments in the neutron sector. We propose two additional problems involving ultracold neutrons which could be relevant for improving our current bounds; namely, gravity-resonance spectroscopy and neutron whispering gallery wave.

Non-destructive Faraday imaging of dynamically controlled ultracold atoms

NASA Astrophysics Data System (ADS)

Gajdacz, Miroslav; Pedersen, Poul; Mørch, Troels; Hilliard, Andrew; Arlt, Jan; Sherson, Jacob

2013-05-01

We investigate non-destructive measurements of ultra-cold atomic clouds based on dark field imaging of spatially resolved Faraday rotation. In particular, we pursue applications to dynamically controlled ultracold atoms. The dependence of the Faraday signal on laser detuning, atomic density and temperature is characterized in a detailed comparison with theory. In particular the destructivity per measurement is extremely low and we illustrate this by imaging the same cloud up to 2000 times. The technique is applied to avoid the effect of shot-to-shot fluctuations in atom number calibration. Adding dynamic changes to system parameters, we demonstrate single-run vector magnetic field imaging and single-run spatial imaging of the system's dynamic behavior. The method can be implemented particularly easily in standard imaging systems by the insertion of an extra polarizing beam splitter. These results are steps towards quantum state engineering using feedback control of ultracold atoms.

High-resolution internal state control of ultracold 23Na87Rb molecules

NASA Astrophysics Data System (ADS)

Guo, Mingyang; Ye, Xin; He, Junyu; Quéméner, Goulven; Wang, Dajun

2018-02-01

We report the full internal state control of ultracold 23Na87Rb molecules, including vibrational, rotational, and hyperfine degrees of freedom. Starting from a sample of weakly bound Feshbach molecules, we realize the creation of molecules in single hyperfine levels of both the rovibrational ground and excited states with a high-efficiency and high-resolution stimulated Raman adiabatic passage. This capability brings broad possibilities for investigating ultracold polar molecules with different chemical reactivities and interactions with a single molecular species. Moreover, starting from the rovibrational and hyperfine ground state, we achieve rotational and hyperfine control with one- and two-photon microwave spectroscopy to reach levels not accessible by the stimulated Raman transfer. The combination of these two techniques results in complete control over the internal state of ultracold polar molecules, which paves the way to study state-dependent molecular collisions and state-controlled chemical reactions.

Synthetic Spin-Orbit and Light Field Coupling in Ultra-cold Quantum Gases

NASA Astrophysics Data System (ADS)

Dong, Lin

Ultra-cold quantum gases subjected to light-induced synthetic gauge potentials have become an emergent field of theoretical and experimental studies. Because of the novel application of two-photon Raman transitions, ultra-cold neutral atoms behave like charged particles in magnetic field. The Raman coupling naturally gives rise to an effective spin-orbit interaction which couples the atoms center-of-mass motion to its selected pseudo-spin degrees of freedom. Combined with unprecedented controllability of interactions, geometry, disorder strength, spectroscopy, and high resolution measurement of momentum distribution, etc., we are truly in an exciting era of fulfilling and going beyond Richard Feynman's vision. of realizing quantum simulators to better understand the quantum mechanical nature of the universe, manifested immensely in the ultra-cold regimes. In this dissertation, we present a collection of theoretical progresses made by the doctoral candidate and his colleagues and collaborators. From the past few years of work, we mainly address three aspects of the synthetic spin-orbit and light field induced coupling in ultracold quantum gases: a) The ground-state physics of singleparticle system, two-body bound states, and many-body systems, all of which are subjected to spin-orbit coupling originated from synthetic gauge potentials; b) The symmetry breaking, topological phase transition and quench dynamics, which are conveniently offered by the realized experimental setup; c) The proposal and implications of light field induced dynamical spin-orbit coupling for atoms inside optical cavity. Our work represents an important advancement of theoretical understanding to the active research frontier of ultra-cold atom physics with spin-orbit coupling.

Scanning quantum gas atom chip microscopy of strongly correlated and topologically nontrivial materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lev, Benjamin

The SQCRAMscope, Scanning Quantum Cryogenic Atom Microscope, is a novel scanning probe microscope we developed during this DOE fund period. It is now capable of imaging transport in cryogenically cooled solid-state samples, as we have recently demonstrated with iron-based pnictide superconductors. As such, it opens a new frontier in the quantum-based metrology of materials and is the first example of the direct marriage of ultracold AMO physics with condensed matter physics. We predict the SQCRAMscope will become an important element in the toolbox for exploring strongly correlated and topologically nontrivial materials.

Atom chip gravimeter

NASA Astrophysics Data System (ADS)

Schubert, Christian; Abend, Sven; Gebbe, Martina; Gersemann, Matthias; Ahlers, Holger; Müntinga, Hauke; Matthias, Jonas; Sahelgozin, Maral; Herr, Waldemar; Lämmerzahl, Claus; Ertmer, Wolfgang; Rasel, Ernst

2016-04-01

Atom interferometry has developed into a tool for measuring rotations [1], accelerations [2], and testing fundamental physics [3]. Gravimeters based on laser cooled atoms demonstrated residual uncertainties of few microgal [2,4] and were simplified for field applications [5]. Atomic gravimeters rely on the interference of matter waves which are coherently manipulated by laser light fields. The latter can be interpreted as rulers to which the position of the atoms is compared. At three points in time separated by a free evolution, the light fields are pulsed onto the atoms. First, a coherent superposition of two momentum states is produced, then the momentum is inverted, and finally the two trajectories are recombined. Depending on the acceleration the atoms experienced, the number of atoms detected in the output ports will change. Consequently, the acceleration can be determined from the output signal. The laser cooled atoms with microkelvin temperatures used in state-of-the-art gravimeters impose limits on the accuracy [4]. Therefore, ultra-cold atoms generated by Bose-Einstein condensation and delta-kick collimation [6,7] are expected to be the key for further improvements. These sources suffered from a low flux implying an incompatible noise floor, but a competitive performance was demonstrated recently with atom chips [8]. In the compact and robust setup constructed for operation in the drop tower [6] we demonstrated all steps necessary for an atom chip gravimeter with Bose-Einstein condensates in a ground based operation. We will discuss the principle of operation, the current performance, and the perspectives to supersede the state of the art. The authors thank the QUANTUS cooperation for contributions to the drop tower project in the earlier stages. This work is supported by the German Space Agency (DLR) with funds provided by the Federal Ministry for Economic Affairs and Energy (BMWi) due to an enactment of the German Bundestag under grant numbers DLR 50WM1552-1557 (QUANTUS-IV-Fallturm) and by the Deutsche Forschungsgemeinschaft in the framework of the SFB 1128 geo-Q. [1] P. Berg et al., Composite-Light-Pulse Technique for High-Precision Atom Interferometry, Phys. Rev. Lett., 114, 063002, 2015. [2] A. Peters et al., Measurement of gravitational acceleration by dropping atoms, Nature 400, 849, 1999. [3] D. Schlippert et al., Quantum Test of the Universality of Free Fall, Phys. Rev. Lett., 112, 203002, 2014. [4] A. Louchet-Chauvet et al., The influence of transverse motion within an atomic gravimeter, New J. Phys. 13, 065026, 2011. [5] Q. Bodart et al., A cold atom pyramidal gravimeter with a single laser beam, Appl. Phys. Lett. 96, 134101, 2010. [6] H. Müntinga et al., Interferometry with Bose-Einstein Condensates in Microgravity, Phys. Rev. Lett., 110, 093602, 2013. [7] T. Kovachy et al., Matter Wave Lensing to Picokelvin Temperatures, Phys. Rev. Lett. 114, 143004, 2015. [8] J. Rudolph et al., A high-flux BEC source for mobile atom interferometers, New J. Phys. 17, 065001, 2015.

Nonclassical and semiclassical para-Bose states

NASA Astrophysics Data System (ADS)

Huerta Alderete, C.; Villanueva Vergara, Liliana; Rodríguez-Lara, B. M.

2017-04-01

Motivated by the proposal to simulate para-Bose oscillators in a trapped-ion setup [C. Huerta Alderete and B. M. Rodríguez-Lara, Phys. Rev. A 95, 013820 (2017), 10.1103/PhysRevA.95.013820], we introduce an overcomplete, nonorthogonal basis for para-Bose Hilbert spaces. The states spanning these bases can be experimentally realized in the trapped-ion simulation via time evolution. The para-Bose states show both nonclassical and semiclassical statistics on their Fock state distribution, asymmetric field quadrature variances, and do not minimize the uncertainty relation for the field quadratures. These properties are analytically controlled by the para-Bose order and the evolution time; both parameters might be feasible for fine tuning in the trapped-ion quantum simulation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Demidov, V. E.; Dzyapko, O.; Demokritov, S. O.

The room-temperature dynamics of a magnon gas driven by short microwave pumping pulses is studied. An overpopulation of the lowest energy level of the system following the pumping is observed. Using the sensitivity of the Brillouin light scattering technique to the coherence degree of the scattering magnons we demonstrate the spontaneous emergence of coherence of the magnons at the lowest level, if their density exceeds a critical value. This finding is clear proof of the quantum nature of the observed phenomenon and direct evidence of Bose-Einstein condensation of magnons at room temperature.

Spectral Function and Quasiparticle Damping of Interacting Bosons in Two Dimensions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sinner, Andreas; Kopietz, Peter; Hasselmann, Nils

2009-03-27

We employ the functional renormalization group to study dynamical properties of the two-dimensional Bose gas. Our approach is free of infrared divergences, which plague the usual diagrammatic approaches, and is consistent with the exact Nepomnyashchy identity, which states that the anomalous self-energy vanishes at zero frequency and momentum. We recover the correct infrared behavior of the propagators and present explicit results for the spectral line shape, from which we extract the quasiparticle dispersion and dampi0008.

Einstein–Bose condensation of Onsager vortices

NASA Astrophysics Data System (ADS)

Valani, Rahil N.; Groszek, Andrew J.; Simula, Tapio P.

2018-05-01

We have studied statistical mechanics of a gas of vortices in two dimensions. We introduce a new observable—a condensate fraction of Onsager vortices—to quantify the emergence of the vortex condensate. The condensation of Onsager vortices is most transparently observed in a single vortex species system and occurs due to a competition between solid body rotation (see vortex lattice) and potential flow (see multiple quantum vortex state). We propose an experiment to observe the condensation transition of the vortices in such a single vortex species system.

Manufacturing a thin wire electrostatic trap for ultracold polar molecules.

PubMed

Kleinert, J; Haimberger, C; Zabawa, P J; Bigelow, N P

2007-11-01

We present a detailed description on how to build a thin wire electrostatic trap (TWIST) for ultracold polar molecules. It is the first design of an electrostatic trap that can be superimposed directly onto a magneto-optical trap (MOT). We can thus continuously produce ultracold polar molecules via photoassociation from a two species MOT and instantaneously trap them in the TWIST without the need for complex transfer schemes. Despite the spatial overlap of the TWIST and the MOT, the two traps can be operated and optimized completely independently due to the complementary nature of the utilized trapping mechanisms.

Trapping of ultracold polar molecules with a thin-wire electrostatic trap.

PubMed

Kleinert, J; Haimberger, C; Zabawa, P J; Bigelow, N P

2007-10-05

We describe the realization of a dc electric-field trap for ultracold polar molecules, the thin-wire electrostatic trap (TWIST). The thin wires that form the electrodes of the TWIST allow us to superimpose the trap onto a magneto-optical trap (MOT). In our experiment, ultracold polar NaCs molecules in their electronic ground state are created in the MOT via photoassociation, achieving a continuous accumulation in the TWIST of molecules in low-field seeking states. Initial measurements show that the TWIST trap lifetime is limited only by the background pressure in the chamber.

Preparation of Ultracold Atom Clouds at the Shot Noise Level.

PubMed

Gajdacz, M; Hilliard, A J; Kristensen, M A; Pedersen, P L; Klempt, C; Arlt, J J; Sherson, J F

2016-08-12

We prepare number stabilized ultracold atom clouds through the real-time analysis of nondestructive images and the application of feedback. In our experiments, the atom number N∼10^{6} is determined by high precision Faraday imaging with uncertainty ΔN below the shot noise level, i.e., ΔN

Topological phase transition in the quench dynamics of a one-dimensional Fermi gas with spin-orbit coupling

NASA Astrophysics Data System (ADS)

Wang, Pei; Yi, Wei; Xianlong, Gao

2015-01-01

We study the quench dynamics of a one-dimensional ultracold Fermi gas with synthetic spin-orbit coupling. At equilibrium, the ground state of the system can undergo a topological phase transition and become a topological superfluid with Majorana edge states. As the interaction is quenched near the topological phase boundary, we identify an interesting dynamical phase transition of the quenched state in the long-time limit, characterized by an abrupt change of the pairing gap at a critical quenched interaction strength. We further demonstrate the topological nature of this dynamical phase transition from edge-state analysis of the quenched states. Our findings provide interesting clues for the understanding of topological phase transitions in dynamical processes, and can be useful for the dynamical detection of Majorana edge states in corresponding systems.

Visualizing the BEC-BCS crossover in a two-dimensional Fermi gas: Pairing gaps and dynamical response functions from ab initio computations

NASA Astrophysics Data System (ADS)

Vitali, Ettore; Shi, Hao; Qin, Mingpu; Zhang, Shiwei

2017-12-01

Experiments with ultracold atoms provide a highly controllable laboratory setting with many unique opportunities for precision exploration of quantum many-body phenomena. The nature of such systems, with strong interaction and quantum entanglement, makes reliable theoretical calculations challenging. Especially difficult are excitation and dynamical properties, which are often the most directly relevant to experiment. We carry out exact numerical calculations, by Monte Carlo sampling of imaginary-time propagation of Slater determinants, to compute the pairing gap in the two-dimensional Fermi gas from first principles. Applying state-of-the-art analytic continuation techniques, we obtain the spectral function and the density and spin structure factors providing unique tools to visualize the BEC-BCS crossover. These quantities will allow for a direct comparison with experiments.

Selfbound quantum droplets

NASA Astrophysics Data System (ADS)

Langen, Tim; Wenzel, Matthias; Schmitt, Matthias; Boettcher, Fabian; Buehner, Carl; Ferrier-Barbut, Igor; Pfau, Tilman

2017-04-01

Self-bound many-body systems are formed through a balance of attractive and repulsive forces and occur in many physical scenarios. Liquid droplets are an example of a self-bound system, formed by a balance of the mutual attractive and repulsive forces that derive from different components of the inter-particle potential. On the basis of the recent finding that an unstable bosonic dipolar gas can be stabilized by a repulsive many-body term, it was predicted that three-dimensional self-bound quantum droplets of magnetic atoms should exist. Here we report on the observation of such droplets using dysprosium atoms, with densities 108 times lower than a helium droplet, in a trap-free levitation field. We find that this dilute magnetic quantum liquid requires a minimum, critical number of atoms, below which the liquid evaporates into an expanding gas as a result of the quantum pressure of the individual constituents. Consequently, around this critical atom number we observe an interaction-driven phase transition between a gas and a self-bound liquid in the quantum degenerate regime with ultracold atoms.

Transnational Quantum: Quantum Physics in India through the Lens of Satyendranath Bose

NASA Astrophysics Data System (ADS)

Banerjee, Somaditya

2016-08-01

This paper traces the social and cultural dimensions of quantum physics in colonial India where Satyendranath Bose worked. By focusing on Bose's approach towards the quantum and his collaboration with Albert Einstein, I argue that his physics displayed both the localities of doing science in early twentieth century India as well as a cosmopolitan dimension. He transformed the fundamental new concept of the light quantum developed by Einstein in 1905 within the social and political context of colonial India. This cross-pollination of the local with the global is termed here as the locally rooted cosmopolitan nature of Bose's science. The production of new knowledge through quantum statistics by Bose show the co-constructed nature of physics and the transnational nature of the quantum.

ALMA OBSERVATIONS OF THE COLDEST PLACE IN THE UNIVERSE: THE BOOMERANG NEBULA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sahai, R.; Vlemmings, W. H. T.; Huggins, P. J.

The Boomerang Nebula is the coldest known object in the universe, and an extreme member of the class of pre-planetary nebulae, objects which represent a short-lived transitional phase between the asymptotic giant branch and planetary nebula evolutionary stages. Previous single-dish CO (J = 1-0) observations (with a 45'' beam) showed that the high-speed outflow in this object has cooled to a temperature significantly below the temperature of the cosmic background radiation. Here we report the first observations of the Boomerang Nebula with ALMA in the CO J = 2-1 and J = 1-0 lines to resolve the structure of thismore » ultra-cold nebula. We find a central hourglass-shaped nebula surrounded by a patchy, but roughly round, cold high-velocity outflow. We compare the ALMA data with visible-light images obtained with the Hubble Space Telescope and confirm that the limb-brightened bipolar lobes seen in these data represent hollow cavities with dense walls of molecular gas and dust producing both the molecular-emission-line and scattered-light structures seen at millimeter and visible wavelengths. The large diffuse biconical shape of the nebula seen in the visible wavelength range is likely due to preferential illumination of the cold, high-velocity outflow. We find a compact source of millimeter-wave continuum in the nebular waist—these data, together with sensitive upper limits on the radio continuum using observations with ATCA, indicate the presence of a substantial mass of very large (millimeter-sized) grains in the waist of the nebula. Another unanticipated result is the detection of CO emission regions beyond the ultra-cold region which indicate the re-warming of the cold gas, most likely due to photoelectric grain heating.« less

ALMA Observations of the Coldest Place in the Universe: The Boomerang Nebula

NASA Astrophysics Data System (ADS)

Sahai, R.; Vlemmings, W. H. T.; Huggins, P. J.; Nyman, L.-Å.; Gonidakis, I.

2013-11-01

The Boomerang Nebula is the coldest known object in the universe, and an extreme member of the class of pre-planetary nebulae, objects which represent a short-lived transitional phase between the asymptotic giant branch and planetary nebula evolutionary stages. Previous single-dish CO (J = 1-0) observations (with a 45'' beam) showed that the high-speed outflow in this object has cooled to a temperature significantly below the temperature of the cosmic background radiation. Here we report the first observations of the Boomerang Nebula with ALMA in the CO J = 2-1 and J = 1-0 lines to resolve the structure of this ultra-cold nebula. We find a central hourglass-shaped nebula surrounded by a patchy, but roughly round, cold high-velocity outflow. We compare the ALMA data with visible-light images obtained with the Hubble Space Telescope and confirm that the limb-brightened bipolar lobes seen in these data represent hollow cavities with dense walls of molecular gas and dust producing both the molecular-emission-line and scattered-light structures seen at millimeter and visible wavelengths. The large diffuse biconical shape of the nebula seen in the visible wavelength range is likely due to preferential illumination of the cold, high-velocity outflow. We find a compact source of millimeter-wave continuum in the nebular waist—these data, together with sensitive upper limits on the radio continuum using observations with ATCA, indicate the presence of a substantial mass of very large (millimeter-sized) grains in the waist of the nebula. Another unanticipated result is the detection of CO emission regions beyond the ultra-cold region which indicate the re-warming of the cold gas, most likely due to photoelectric grain heating.

Enhancing light-atom interactions via atomic bunching

NASA Astrophysics Data System (ADS)

Schmittberger, Bonnie L.; Gauthier, Daniel J.

2014-07-01

There is a broad interest in enhancing the strength of light-atom interactions to the point where injecting a single photon induces a nonlinear material response. Here we show theoretically that sub-Doppler-cooled two-level atoms that are spatially organized by weak optical fields give rise to a nonlinear material response that is greatly enhanced beyond that attainable in a homogeneous gas. Specifically, in the regime where the intensity of the applied optical fields is much less than the off-resonance saturation intensity, we show that the third-order nonlinear susceptibility scales inversely with atomic temperature and, due to this scaling, can be two orders of magnitude larger than that of a homogeneous gas for typical experimental parameters. As a result, we predict that spatially bunched two-level atoms can exhibit single-photon nonlinearities. Our model is valid for all regimes of atomic bunching and simultaneously accounts for the backaction of the atoms on the optical fields. Our results agree with previous theoretical and experimental results for light-atom interactions that have considered only limited regimes of atomic bunching. For lattice beams tuned to the low-frequency side of the atomic transition, we find that the nonlinearity transitions from a self-focusing type to a self-defocusing type at a critical intensity. We also show that higher than third-order nonlinear optical susceptibilities are significant in the regime where the dipole potential energy is on the order of the atomic thermal energy. We therefore find that it is crucial to retain high-order nonlinearities to accurately predict interactions of laser fields with spatially organized ultracold atoms. The model presented here is a foundation for modeling low-light-level nonlinear optical processes for ultracold atoms in optical lattices.

Chemical potentials and thermodynamic characteristics of ideal Bose- and Fermi-gases in the region of quantum degeneracy

NASA Astrophysics Data System (ADS)

Sotnikov, A. G.; Sereda, K. V.; Slyusarenko, Yu. V.

2017-01-01

Calculations of chemical potentials for ideal monatomic gases with Bose-Einstein and Fermi-Dirac statistics as functions of temperature, across the temperature region that is typical for the collective quantum degeneracy effect, are presented. Numerical calculations are performed without any additional approximations, and explicit dependences of the chemical potentials on temperature are constructed at a fixed density of gas particles. Approximate polynomial dependences of chemical potentials on temperature are obtained that allow for the results to be used in further studies without re-applying the involved numerical methods. The ease of using the obtained representations is demonstrated on examples of deformation of distribution for a population of energy states at low temperatures, and on the impact of quantum statistics (exchange interaction) on the equations of state for ideal gases and some of the thermodynamic properties thereof. The results of this study essentially unify two opposite limiting cases in an intermediate region that are used to describe the equilibrium states of ideal gases, which are well known from university courses on statistical physics, thus adding value from an educational point of view.

Topological interface physics in spinor Bose-Einstein condensates

NASA Astrophysics Data System (ADS)

Borgh, Magnus; Ruostekoski, Janne

2013-05-01

We present an experimentally viable scheme whereby the physics of coherent interfaces between topologically distinct regions can be studied in an atomic quantum gas. The interface engineering is achieved using the internal spin structures of atoms together with local control over interaction strengths. We consider a coherent interface between polar and ferromagnetic regions of a spin-1 Bose-Einstein condensate and show that defects representing different topologies can connect continuously across the boundary. We show that energy minimization leads to nontrivial interface-crossing defect structures, demonstrating how the method can be used to study stability properties of field-theoretical solitons. We demonstrate, e.g., the formation of a half-quantum vortex arch, an Alice arch, on the interface, exhibiting the topological charge of a point defect. We also demonstrate an energetically stable connection of a coreless vortex to two half-quantum vortices. Our method can be extended to study interface physics in spin-2 and spin-3 BECs with richer phenomenology, or in strongly correlated optical-lattice systems. We acknowledge financial support from the Leverhulme Trust.

Atom-chip based quantum gravimetry for the precise determination of absolute local gravity

NASA Astrophysics Data System (ADS)

Abend, S.

2015-12-01

We present a novel technique for the precise measurement of absolute local gravity based on cold atom interferometry. Atom interferometry utilizes the interference of matter waves interrogated by laser light to read out inertial forces. Today's generation of these devices typically operate with test mass samples, that consists of ensembles of laser cooled atoms. Their performance is limited by the velocity spread and finite-size of the test masses that impose systematic uncertainties at the level of a few μGal. Rather than laser cooled atoms we employ quantum degenerate ensembles, so called Bose-Einstein condensates, as ultra-sensitive probes for gravity. These sources offer unique properties in temperature as well as in ensemble size that will allow to overcome the current limitations with the next generation of sensors. Furthermore, atom-chip technologies offer the possibility to generate Bose-Einstein condensates in a fast and reliable way. We show a lab-based prototype that uses the atom-chip itself to retro-reflect the interrogation laser and thus serving as inertial reference inside the vacuum. With this setup it is possible to demonstrate all necessary steps to measure gravity, including the preparation of the source, spanning an interferometer as well as the detection of the output signal, within an area of 1 cm3 right below the atom-chip and to analyze relevant systematic effects. In the framework of the center of excellence geoQ a next generation device is under construction at the Institut für Quantenoptik, that will allow for in-field measurements. This device will feature a state-of-the-art atom-chip source with a high-flux of ultra-cold atoms at a repetition rate of 1-2 Hz. In cooperation with the Müller group at the Institut für Erdmessung the sensor will be characterized in the laboratory first, to be ultimately employed in campaigns to measure the Fennoscandian uplift at the level of 1 μGal. The presented work is part of the center of excellence geoQ (SFB 1128), funded by the Deutsche Forschungsgemeinschaft (DFG). This work is supported by the German Space Agency (DLR) with funds provided by the Federal Ministry for Economic Affairs and Energy (BMWi) due to an enactment of the German Bundestag under grant numbers DLR 50 1131-1137 (QUANTUS-III).

Ultracold atoms in an optical lattice one millimeter from air

NASA Astrophysics Data System (ADS)

Jervis, Dylan; Edge, Graham; Trotzky, Stefan; McKay, David; Thywissen, Joseph

2013-05-01

Over the past decade, ultracold atoms in optical lattices have shown to be versatile systems able to realize canonical Hamiltonians of condensed matter. High-resolution in-situ imaging of ultracold clouds has furthermore enabled thermometry, equation of state measurements, direct measurement of fluctuations, and unprecedented control. We report on microscopy of ultracold bosons and fermions in a novel configuration where the atoms are harmonically trapped 800 microns away from a 200 micron-thick vacuum window. This window also serves as a retro-reflecting mirror for an optical lattice, into which the atoms can be loaded. Two additional transverse standing waves complete the three-dimensional lattice setup. In free space, we have shown that laser cooling with 405 nm light, on the open 4S1/2-5P3/2 transition, allows for temperatures below the Doppler temperature of the 4S1/2-4P3/2 cycling transition at 767 nm. Microscopy with 405 nm light furthermore reduces the diffraction limit of in-situ imaging.

Observation of Feshbach resonances between ultracold Na and Rb atoms

NASA Astrophysics Data System (ADS)

Wang, Fudong; Xiong, Dezhi; Li, Xiaoke; Wang, Dajun

2013-03-01

Absolute ground-state 23Na87Rb molecule has a large electric dipole moment of 3.3 Debye and its two body exchange chemical reaction is energetically forbidden at ultracold temperatures. It is thus a nice candidate for studying quantum gases with dipolar interactions. We have built an experiment setup to investigate ultracold collisions between Na and Rb atoms as a first step toward the production of ground state molecular samples. Ultracold mixtures are first obtained by evaporative cooling of Rb and sympathetic cooling of Na. They are then transferred to a crossed dipole trap and prepared in different spin combinations for Feshbach resonance study. Several resonances below 1000 G are observed with both atoms prepared in either | F = 1,mF = 1 > or | F = 1,mF = - 1 > hyperfine states. Most of them are within 30 G of predicted values§ based on potentials obtained by high quality molecular spectroscopy studies. This work is supported by RGC Hong Kong. § E. Tiemann, private communications

Dipolar collisions of ultracold 23Na87Rb molecules.

NASA Astrophysics Data System (ADS)

Guo, Mingyang; Ye, Xin; He, Junyu; Quéméner, Goulven; González-Martínez, Maykel; Dulieu, Olivier; Wang, Dajun

2017-04-01

Although ultracold polar molecules have long been proposed as a primary candidate for investigating dipolar many body physics, many of their basic properties, like their collisions in external electric fields, are still largely unknown. In fact, despite the successful production of several new ultracold molecular species in the last two years, so far the only available dipolar collision data is still from JILA's fermionic 40K87Rb experiment in 2010. In this talk, we will describe our investigation on dipolar collisions of ultracold bosonic and chemically stable 23Na87Rb molecules which possess a large permanent electric dipole moment. With a moderate electric field, an effective dipole moment large enough to strongly couple higher partial waves into the collisions can be achieved. We will report the influence of this effect on the molecular collisions observed in our experiment. Our theoretical model for understanding these observations will also be presented. This work is supported by the Hong Kong RGC CUHK404712 and the ANR/RGC Joint Research Scheme ACUHK403/13.

The geometric phase controls ultracold chemistry

DOE PAGES

Kendrick, B. K.; Hazra, Jisha; Balakrishnan, N.

2015-07-30

In this study, the geometric phase is shown to control the outcome of an ultracold chemical reaction. The control is a direct consequence of the sign change on the interference term between two scattering pathways (direct and looping), which contribute to the reactive collision process in the presence of a conical intersection (point of degeneracy between two Born–Oppenheimer electronic potential energy surfaces). The unique properties of the ultracold energy regime lead to an effective quantization of the scattering phase shift enabling maximum constructive or destructive interference between the two pathways. By taking the O + OH → H + Omore » 2 reaction as an illustrative example, it is shown that inclusion of the geometric phase modifies ultracold reaction rates by nearly two orders of magnitude. Interesting experimental control possibilities include the application of external electric and magnetic fields that might be used to exploit the geometric phase effect reported here and experimentally switch on or off the reactivity.« less

Ab initio study of the neutral and anionic alkali and alkaline earth hydroxides: Electronic structure and prospects for sympathetic cooling of OH−

PubMed Central

2017-01-01

We have performed a systematic ab initio study on alkali and alkaline earth hydroxide neutral (MOH) and anionic (MOH−) species where M = Li, Na, K, Rb, Cs or Be, Mg, Ca, Sr, Ba. The CCSD(T) method with extended basis sets and Dirac-Fock relativistic effective core potentials for the heavier atoms has been used to study their equilibrium geometries, interaction energies, electron affinities, electric dipole moment, and potential energy surfaces. All neutral and anionic species exhibit a linear shape with the exception of BeOH, BeOH−, and MgOH−, for which the equilibrium structure is found to be bent. Our analysis shows that the alkaline earth hydroxide anions are valence-bound whereas the alkali hydroxide anions are dipole bound. In the context of sympathetic cooling of OH− by collision with ultracold alkali and alkaline earth atoms, we investigate the 2D MOH− potential energy surfaces and the associative detachment reaction M + OH→− MOH + e−, which is the only energetically allowed reactive channel in the cold regime. We discuss the implication for the sympathetic cooling of OH− and conclude that Li and K are the best candidates for an ultracold buffer gas. PMID:28527437

Trapping ultracold gases near cryogenic materials with rapid reconfigurability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Naides, Matthew A.; Turner, Richard W.; Lai, Ruby A.

We demonstrate an atom chip trapping system that allows the placement and high-resolution imaging of ultracold atoms within microns from any ≲100 μm-thin, UHV-compatible material, while also allowing sample exchange with minimal experimental downtime. The sample is not connected to the atom chip, allowing rapid exchange without perturbing the atom chip or laser cooling apparatus. Exchange of the sample and retrapping of atoms has been performed within a week turnaround, limited only by chamber baking. Moreover, the decoupling of sample and atom chip provides the ability to independently tune the sample temperature and its position with respect to the trapped ultracoldmore » gas, which itself may remain in the focus of a high-resolution imaging system. As a first demonstration of this system, we have confined a 700-nK cloud of 8 × 10{sup 4} {sup 87}Rb atoms within 100 μm of a gold-mirrored 100-μm-thick silicon substrate. The substrate was cooled to 35 K without use of a heat shield, while the atom chip, 120 μm away, remained at room temperature. Atoms may be imaged and retrapped every 16 s, allowing rapid data collection.« less

Ultracold Chemical Reactions of a Single Rydberg Atom in a Dense Gas

DOE PAGES

Schlagmüller, Michael; Liebisch, Tara Cubel; Engel, Felix; ...

2016-08-10

Within a dense environment (ρ ≈ 10 14 atoms/cm 3) at ultracold temperatures (T < 1 μK), a single atom excited to a Rydberg state acts as a reaction center for surrounding neutral atoms. At these temperatures, almost all neutral atoms within the Rydberg orbit are bound to the Rydberg core and interact with the Rydberg atom. We have studied the reaction rate and products for nS 87Rb Rydberg states, and we mainly observe a state change of the Rydberg electron to a high orbital angular momentum l, with the released energy being converted into kinetic energy of the Rydberg atom. Unexpectedly, the measurements show a threshold behavior at n ≈ 100 for the inelastic collision time leading to increased lifetimes of the Rydberg state independent of the densities investigated. Even at very high densities (ρ ≈ 4.8 x 10 14 cm -3), the lifetime of a Rydberg atom exceeds 10 μs at n > 140 compared to 1 μs at n = 90. In addition, a second observed reaction mechanism, namely, Rbmore » $$+\\atop{2}$$ molecule formation, was studied. Both reaction products are equally probable for n = 40, but the fraction of Rb + 2 created drops to below 10% for n ≥ 90.« less

PREFACE Preface

NASA Astrophysics Data System (ADS)

Bachor, Hans; Drummond, Peter; Hannaford, Peter

2011-01-01

The 22nd International Conference on Atomic Physics (ICAP 2010) was held from 25 to 30 July, 2010 in Cairns, Tropical North Queensland, Australia. This conference followed on from the series of highly successful biennial ICAP conferences held in Storrs, Innsbruck, Rio, Cambridge MA, Florence, Windsor, Amsterdam, Boulder, Munich, Ann Arbor, Paris, Tokyo, Seattle, Göteborg, Cambridge MA, Riga, Berkeley, Heidelberg, Boulder, Oxford and New York. ICAP 2010 was attended by 630 participants from 37 countries. The conference presented an outstanding program of papers covering the most recent advances in atomic physics, including atomic tests of fundamental physics and basic symmetries; precision measurements, including atomic clocks, atom interferometers and fundamental constants; ultracold gases and Bose-Einstein condensates; ultracold Fermi gases; ultracold molecules; quantum simulators with atoms and ions; few-body systems; ultrafast phenomena and free electron lasers; quantum information with atoms and ions; quantum optics and cavity QED with atoms; and hybrid and optomechanical systems. The papers in this Proceedings represent a collection of the invited talks. The conference program consisted of 48 invited talks presented in plenary sessions, including 10 'hot topic' talks highlighting the most recent advances in the field, and about 490 poster papers presented in three afternoon sessions. The program included talks by Nobel Laureates Claude Cohen-Tannoudji, Wolfgang Ketterle and Bill Phillips, a memorium talk commemorating the scientific life of Vladilen Letokhov, and an evening lecture by Alain Aspect on 'Wave particle duality for a single photon: quantum weirdness brought to light'. The conference was preceded by a two-day workshop in Cairns on Variation of Fundamental Constants and Violation of Fundamental Symmetries P, T(EDM), CPT, Lorentz Invariance, organised by the University of New South Wales; and three-day Student Workshop at Cape Tribulation, organized by the Australian Research Council Centre of Excellence for Quantum-Atom Optics (ACQAO). A website with full details of the conference program, abstracts and other information can be found at: http://www.swin.edu.au/icap2010. We would like to thank the participants, especially those who contributed talks, posters and manuscripts, for making ICAP2010 such an exciting and memorable conference. We thank the Program Committee for putting together an outstanding program and the ICAP International Advisory Committee for their expert advice and suggestions. We gratefully acknowledge the financial support of our sponsors: the Australian National University, the Australian Research Council Centre of Excellence for Quantum-Atom Optics, Griffith University, the Ian Potter Foundation, the International Union of Pure and Applied Physics, the National Institute of Standards and Technology, Swinburne University of Technology, and contributors to the trade exhibition: Coherent, Coherent Scientific, the Institute of Physics Publishing, Lastek, NewSpec, Nufern, Oxford University Press, Spectra-Physics, Springer, Toptica Photonics and Warsash Scientific. Finally, we thank our Conference Secretariat, Maria Lamari, and the Local Organising Committee for their tireless and expert efforts in the organisation of ICAP2010, and the staff of the Cairns Convention Centre, whose friendly and efficient service contributed much to the success of the conference. The next ICAP conference is planned to be held in Palaiseau, France from 23 to 27 July 2012 (http://www.ifraf.org/icap2012). Hans BachorPeter DrummondPeter HannafordEditors

Control of Ultracold Photodissociation with Magnetic Fields

NASA Astrophysics Data System (ADS)

McDonald, M.; Majewska, I.; Lee, C.-H.; Kondov, S. S.; McGuyer, B. H.; Moszynski, R.; Zelevinsky, T.

2018-01-01

Photodissociation of a molecule produces a spatial distribution of photofragments determined by the molecular structure and the characteristics of the dissociating light. Performing this basic reaction at ultracold temperatures allows its quantum mechanical features to dominate. In this regime, weak applied fields can be used to control the reaction. Here, we photodissociate ultracold diatomic strontium in magnetic fields below 10 G and observe striking changes in photofragment angular distributions. The observations are in excellent agreement with a multichannel quantum chemistry model that includes nonadiabatic effects and predicts strong mixing of partial waves in the photofragment energy continuum. The experiment is enabled by precise quantum-state control of the molecules.

Self-diffusion and conductivity in an ultracold strongly coupled plasma: Calculation by the method of molecular dynamics

NASA Astrophysics Data System (ADS)

Zelener, B. B.; Zelener, B. V.; Manykin, E. A.; Bronin, S. Ya; Bobrov, A. A.; Khikhlukha, D. R.

2018-01-01

We present results of calculations by the method of molecular dynamics of self-diffusion and conductivity of electron and ion components of ultracold plasma in a comparison with available theoretical and experimental data. For the ion self-diffusion coefficient, good agreement was obtained with experiments on ultracold plasma. The results of the calculation of self-diffusion also agree well with other calculations performed for the same values of the coupling parameter, but at high temperatures. The difference in the results of the conductivity calculations on the basis of the current autocorrelation function and on the basis of the diffusion coefficient is discussed.

Dirty bosons in a three-dimensional harmonic trap

NASA Astrophysics Data System (ADS)

Khellil, Tama; Pelster, Axel

2017-09-01

We study a three-dimensional Bose-Einstein condensate in an isotropic harmonic trapping potential with an additional delta-correlated disorder potential and investigate the emergence of a Bose-glass phase for increasing disorder strength. At zero temperature a first-order quantum phase transition from the superfluid phase to the Bose-glass phase is detected at a critical disorder strength, which agrees with the findings in the literature. Afterwards, we study the interplay between temperature and disorder fluctuations on the respective components of the particle density. In particular, we find for smaller disorder strengths that a superfluid region, a Bose-glass region, and a thermal region coexist. Furthermore, depending on the respective system parameters, three phase transitions are detected, namely, one from the superfluid to the Bose-glass phase, another one from the Bose-glass to the thermal phase, and finally one from the superfluid to the thermal phase. All these results are obtained by extending a quite recent Hartree-Fock mean-field theory for the dirty boson problem, which is based on the replica method, from the homogeneous case to a harmonic confinement.

Induced interaction in a Fermi gas with a BEC-BCS crossover

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu Zengqiang; Huang Kun; Yin Lan

2009-05-15

We study the effect of the induced interaction on the superfluid transition temperature of a Fermi gas with a Bose-Einstein condensation-Bardeen-Cooper-Schrieffer (BEC-BCS) crossover. The Gorkov-Melik-Barkhudarov theory about the induced interaction is extended from the BCS side to the entire crossover and the pairing fluctuation is treated in the approach by Nozieres and Schmitt-Rink. At unitarity, the induced interaction reduces the transition temperature by about 20%. In the BCS limit, the transition temperature is reduced by a factor of about 2.22, as found by Gorkov and Melik-Barkhudarov. Our result shows that the effect of the induced interaction is important both onmore » the BCS side and in the unitary region.« less

Measurement of Ultracold Neutrons Produced by Using Doppler-shifted Bragg Reflection at a Pulsed-neutron Source

DOE R&D Accomplishments Database

Brun, T. O.; Carpenter, J. M.; Krohn, V. E.; Ringo, G. R.; Cronin, J. W.; Dombeck, T. W.; Lynn, J. W.; Werner, S. A.

1979-01-01

Ultracold neutrons (UCN) have been produced at the Argonne pulsed-neutron source by the Doppler shift of 400-m/s neutrons Bragg reflected from a moving crystal. The peak density of UCN produced at the crystal exceeds 0.1 n/cm{sup 3}.

Gap Solitons of Superfluid Fermi Gas in FS Optical Lattices

NASA Astrophysics Data System (ADS)

Chen, Yan; Zhang, Ke-Zhi; He, Yong-Lin; Liu, Zhen-Lai; Zhu, Liao

2018-01-01

By employing the mean-field theory and hydrodynamic scheme, we study the gap solitons of superfluid Fermi gas in Fourier-Synthesized(FS) optical lattices. By means of numerical methods and variational approximation, the atomic interaction, the chemical potential, the potential depth of the lattice and relative phase of the Fermi system are derived along the Bose-Enstein condensation(BEC)side to the Bardeen-Cooper-Schrieffer (BCS)side. It means that the condition exciting gap solitons is obtained. Moreover, we analyze the fundamental gap soltions of the superfluid Fermi gas. It is found that the relative phase α impacts greatly on the properties of fundamental gap solitons for superfluid Fermi gas. Especially, the nonlinearity interaction term g decreases with α. Add, due to Fermi pressure, curvature changes of g in the BEC limit( γ = 1, here, γ is a function of an interaction parameter) is larger than that at unitary ( γ = 2/3). Spatial distribution of gap solitons exhibit very obvious different when the system transit from the BEC side to BCS side.

Soliton resonance in bose-einstein condensate

NASA Technical Reports Server (NTRS)

Zak, Michail; Kulikov, I.

2002-01-01

A new phenomenon in nonlinear dispersive systems, including a Bose-Einstein Condensate (BEC), has been described. It is based upon a resonance between an externally induced soliton and 'eigen-solitons' of the homogeneous cubic Schrodinger equation. There have been shown that a moving source of positive /negative potential induces bright /dark solitons in an attractive / repulsive Bose condensate.

Quantum criticality and universal scaling of strongly attractive spin-imbalanced Fermi gases in a one-dimensional harmonic trap

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yin Xiangguo; Chen Shu; Guan Xiwen

2011-07-15

We investigate quantum criticality and universal scaling of strongly attractive Fermi gases confined in a one-dimensional harmonic trap. We demonstrate from the power-law scaling of the thermodynamic properties that current experiments on this system are capable of measuring universal features at quantum criticality, such as universal scaling and Tomonaga-Luttinger liquid physics. The results also provide insights on recent measurements of key features of the phase diagram of a spin-imbalanced atomic Fermi gas [Y. Liao et al., Nature (London) 467, 567 (2010)] and point to further study of quantum critical phenomena in ultracold atomic Fermi gases.

Comparison of Handaxes from Bose Basin (China) and the Western Acheulean Indicates Convergence of Form, Not Cognitive Differences

PubMed Central

Wang, Wei; Lycett, Stephen J.; von Cramon-Taubadel, Noreen; Jin, Jennie J. H.; Bae, Christopher J.

2012-01-01

Alleged differences between Palaeolithic assemblages from eastern Asia and the west have been the focus of controversial discussion for over half a century, most famously in terms of the so-called ‘Movius Line’. Recent discussion has centered on issues of comparability between handaxes from eastern Asian and ‘Acheulean’ examples from western portions of the Old World. Here, we present a multivariate morphometric analysis in order to more fully document how Mid-Pleistocene (i.e. ∼803 Kyr) handaxes from Bose Basin, China compare to examples from the west, as well as with additional (Mode 1) cores from across the Old World. Results show that handaxes from both the western Old World and Bose are significantly different from the Mode 1 cores, suggesting a gross comparability with regard to functionally-related form. Results also demonstrate overlap between the ranges of shape variation in Acheulean handaxes and those from Bose, demonstrating that neither raw material nor cognitive factors were an absolute impediment to Bose hominins in making comparable handaxe forms to their hominin kin west of the Movius Line. However, the shapes of western handaxes are different from the Bose examples to a statistically significant degree. Moreover, the handaxe assemblages from the western Old World are all more similar to each other than any individual assemblage is to the Bose handaxes. Variation in handaxe form is also comparatively high for the Bose material, consistent with suggestions that they represent an emergent, convergent instance of handaxe technology authored by Pleistocene hominins with cognitive capacities directly comparable to those of ‘Acheulean’ hominins. PMID:22536441

From rotating atomic rings to quantum Hall states.

PubMed

Roncaglia, M; Rizzi, M; Dalibard, J

2011-01-01

Considerable efforts are currently devoted to the preparation of ultracold neutral atoms in the strongly correlated quantum Hall regime. However, the necessary angular momentum is very large and in experiments with rotating traps this means spinning frequencies extremely near to the deconfinement limit; consequently, the required control on parameters turns out to be too stringent. Here we propose instead to follow a dynamic path starting from the gas initially confined in a rotating ring. The large moment of inertia of the ring-shaped fluid facilitates the access to large angular momenta, corresponding to giant vortex states. The trapping potential is then adiabatically transformed into a harmonic confinement, which brings the interacting atomic gas in the desired quantum-Hall regime. We provide numerical evidence that for a broad range of initial angular frequencies, the giant-vortex state is adiabatically connected to the bosonic ν = 1/2 Laughlin state.

Probing the critical exponent of the superfluid fraction in a strongly interacting Fermi gas

NASA Astrophysics Data System (ADS)

Hu, Hui; Liu, Xia-Ji

2013-11-01

We theoretically investigate the critical behavior of a second-sound mode in a harmonically trapped ultracold atomic Fermi gas with resonant interactions. Near the superfluid phase transition with critical temperature Tc, the frequency or the sound velocity of the second-sound mode crucially depends on the critical exponent β of the superfluid fraction. In an isotropic harmonic trap, we predict that the mode frequency diverges like (1-T/Tc)β-1/2 when β<1/2. In a highly elongated trap, the speed of the second sound reduces by a factor of 1/2β+1 from that in a homogeneous three-dimensional superfluid. Our prediction could readily be tested by measurements of second-sound wave propagation in a setup, such as that exploited by Sidorenkov [Nature (London)NATUAS0028-083610.1038/nature12136 498, 78 (2013)] for resonantly interacting lithium-6 atoms, once the experimental precision is improved.

Velocity selection for ultracold atoms using mazer action in a bimodal cavity

NASA Astrophysics Data System (ADS)

Irshad, Afshan; Qamar, Sajid; Qamar, Shahid

2010-01-01

In this paper, we discuss the velocity selection of ultracold three-level atoms in Λ configuration using a mazer. Our model is the same as discussed by Arun et al. [R. Arun, G.S. Agarwal, M.O. Scully, H. Walther, Phys. Rev. A 62 (2000) 023809] for mazer action in a bimodal cavity. We show that the initial Maxwellian velocity distribution of ultracold atoms can be narrowed due to the presence of resonances in the transmission through dressed-state potential. When the atoms are initially prepared in one of the two lower atomic states then significantly better velocity selectivity is obtained due to the presence of dark states.

Frequency standards based on ultracold atoms in tests of general relativity, navigation and gravimetry

NASA Astrophysics Data System (ADS)

Khabarova, K. Yu.; Kudeyarov, K. S.; Kolachevsky, N. N.

2017-06-01

Research and development in the field of optical clocks based on ultracold atoms and ions have enabled the relative uncertainty in frequency to be reduced down to a few parts in 1018. The use of novel, precise frequency comparison methods opens up new possibilities for basic research (sensitive tests of general relativity, a search for a drift of fundamental constants and a search for ‘dark matter’) as well as for state-of-the-art navigation and gravimetry. We discuss the key methods that are used in creating precision clocks (including transportable clocks) based on ultracold atoms and ions and the feasibility of using them in resolving current relativistic gravimetry issues.

The BCS-BEC Crossover

NASA Astrophysics Data System (ADS)

Parish, Meera M.

2015-09-01

This chapter presents the crossover from the Bardeen-Cooper-Schrieffer (BCS) state of weakly correlated pairs of fermions to the Bose-Einstein condensation (BEC) of diatomic molecules in the atomic Fermi gas. Our aim is to provide a pedagogical review of the BCS-BEC crossover, with an emphasis on the basic concepts, particularly those that are not generally known or are difficult to find in the literature. We shall not attempt to give an exhaustive survey of current research in the limited space here; where possible, we will direct the reader to more extensive reviews.

Thermodynamic measurement of the sound velocity of a Bose gas across the transition to Bose–Einstein condensation

NASA Astrophysics Data System (ADS)

Fritsch, A. R.; Tavares, P. E. S.; Vivanco, F. A. J.; Telles, G. D.; Bagnato, V. S.; Henn, E. A. L.

2018-05-01

We present an alternative method for determining the sound velocity in atomic Bose–Einstein condensates, based on thermodynamic global variables. The total number of trapped atoms was as a function of temperature carefully studied across the phase transition, at constant volume. It allowed us to evaluate the sound velocity resulting in consistent values from the quantum to classical regime, in good agreement with previous results found in literature. We also provide some insight about the dominant sound mode (thermal or superfluid) across a wide temperature range.

Correlation and Collective Modes in Narrow Band Materials: NiO and FeO.

DTIC Science & Technology

1981-02-01

reduced and could have been Cu 20. Madey and Hanni have made an estimate of the density of surface bosons nceded to provide the observed shielding of the...and Hanni indicates that acsuming an ideal Bose gas composed of coupled free electrons may overestimate the screening. The electric field in the...the surface state is then T m a e exp m(3.18 2e2dm J e( It is Eq. (3.18) that Madey and Hanni use to fit the experimental data of -6011 -2 Witteborn

Coherent Atom Optics with Optical Potentials: A Summary of New Phenomena with Bose-Einstein Condensates at the University of Arizona

DTIC Science & Technology

2009-10-08

differentially pumped two-cell vacuum system. A gas of Rb atoms, provided by SAES dispensers, fills a glass cell where laser cooling and magneto - optic ...mask [Fig. 1(b)] that was imaged onto the center of the trap . The sum of the magnetic and optical potentials created a triple-well trap , with three... Simulations of BEC growth in a toroidal trap show vortices (as in (b),(c)) and persistent currents. 4 The merging of experimental capabilities. [ongoing work

Rydberg Molecules for Ion-Atom Scattering in the Ultracold Regime

NASA Astrophysics Data System (ADS)

Schmid, T.; Veit, C.; Zuber, N.; Löw, R.; Pfau, T.; Tarana, M.; Tomza, M.

2018-04-01

We propose a novel experimental method to extend the investigation of ion-atom collisions from the so far studied cold, essentially classical regime to the ultracold, quantum regime. The key aspect of this method is the use of Rydberg molecules to initialize the ultracold ion-atom scattering event. We exemplify the proposed method with the lithium ion-atom system, for which we present simulations of how the initial Rydberg molecule wave function, freed by photoionization, evolves in the presence of the ion-atom scattering potential. We predict bounds for the ion-atom scattering length from ab initio calculations of the interaction potential. We demonstrate that, in the predicted bounds, the scattering length can be experimentally determined from the velocity of the scattered wave packet in the case of 6Li+ = 6Li and from the molecular ion fraction in the case of 7Li+ - 7Li. The proposed method to utilize Rydberg molecules for ultracold ion-atom scattering, here particularized for the lithium ion-atom system, is readily applicable to other ion-atom systems as well.

Symmetry and the geometric phase in ultracold hydrogen-exchange reactions

NASA Astrophysics Data System (ADS)

Croft, J. F. E.; Hazra, J.; Balakrishnan, N.; Kendrick, B. K.

2017-08-01

Quantum reactive scattering calculations are reported for the ultracold hydrogen-exchange reaction and its non-reactive atom-exchange isotopic counterparts, proceeding from excited rotational states. It is shown that while the geometric phase (GP) does not necessarily control the reaction to all final states, one can always find final states where it does. For the isotopic counterpart reactions, these states can be used to make a measurement of the GP effect by separately measuring the even and odd symmetry contributions, which experimentally requires nuclear-spin final-state resolution. This follows from symmetry considerations that make the even and odd identical-particle exchange symmetry wavefunctions which include the GP locally equivalent to the opposite symmetry wavefunctions which do not. It is shown how this equivalence can be used to define a constant which quantifies the GP effect and can be obtained solely from experimentally observable rates. This equivalence reflects the important role that discrete symmetries play in ultracold chemistry and highlights the key role that ultracold reactions can play in understanding fundamental aspects of chemical reactivity more generally.

Collisions of ultracold 23Na87Rb molecules with controlled chemical reactivity

NASA Astrophysics Data System (ADS)

Ye, Xin; Guo, Mingyang; He, Junyu; Wang, Dajun; Quemener, Goulven; Gonzalez-Martinez, Maykel; Dulieu, Oliver

2017-04-01

The recent successful creation of several ultracold absolute ground-state polar molecules without chemical reaction channel has opened a new playground for investigating the so far poorly understood collisions between them. On one hand, these collisions are indispensable for the exploration of dipolar physics, on the other hand, they are direct manifestations of the brand-new field of ultracold chemistry. Here, we report on the study on molecular collisions with ultracold ground-state 23Na87Rb molecules prepared by transferring weakly bound Feshbach molecules with STIRAP. By tuning the Raman laser wavelength to control the internal states, samples with distinctly different chemical reactivity and inelastic channels can be prepared. Surprisingly, we found that the trap loss of the non-reactive case is nearly identical to that of the reactive case. We also developed a model based on the collision complex formation mechanism. The comparison between experiment and theory will also be presented. This work was supported by the French ANR/Hong Kong RGC COPOMOL project (Grant No. A-CUHK403/13), the RGC General Research Fund (Grant No. CUHK14301815).

Rydberg Molecules for Ion-Atom Scattering in the Ultracold Regime.

PubMed

Schmid, T; Veit, C; Zuber, N; Löw, R; Pfau, T; Tarana, M; Tomza, M

2018-04-13

We propose a novel experimental method to extend the investigation of ion-atom collisions from the so far studied cold, essentially classical regime to the ultracold, quantum regime. The key aspect of this method is the use of Rydberg molecules to initialize the ultracold ion-atom scattering event. We exemplify the proposed method with the lithium ion-atom system, for which we present simulations of how the initial Rydberg molecule wave function, freed by photoionization, evolves in the presence of the ion-atom scattering potential. We predict bounds for the ion-atom scattering length from ab initio calculations of the interaction potential. We demonstrate that, in the predicted bounds, the scattering length can be experimentally determined from the velocity of the scattered wave packet in the case of ^{6}Li^{+}-^{6}Li and from the molecular ion fraction in the case of ^{7}Li^{+}-^{7}Li. The proposed method to utilize Rydberg molecules for ultracold ion-atom scattering, here particularized for the lithium ion-atom system, is readily applicable to other ion-atom systems as well.

High precision optical spectroscopy and quantum state selected photodissociation of ultracold 88Sr2 molecules in an optical lattice

NASA Astrophysics Data System (ADS)

McDonald, Mickey Patrick

Over the past several decades, rapid progress has been made toward the accurate characterization and control of atoms, made possible largely by the development of narrow-linewidth lasers and techniques for trapping and cooling at ultracold temperatures. Extending this progress to molecules will have exciting implications for chemistry, condensed matter physics, and precision tests of physics beyond the Standard Model. These possibilities are all consequences of the richness of molecular structure, which is governed by physics substantially different from that characterizing atomic structure. This same richness of structure, however, increases the complexity of any molecular experiment manyfold over its atomic counterpart, magnifying the difficulty of everything from trapping and cooling to the comparison of theory with experiment. This thesis describes work performed over the past six years to establish the state of the art in manipulation and quantum control of ultracold molecules. Our molecules are produced via photoassociation of ultracold strontium atoms followed by spontaneous decay to a stable ground state. We describe a thorough set of measurements characterizing the rovibrational structure of very weakly bound (and therefore very large) 88Sr2 molecules from several different perspectives, including determinations of binding energies; linear, quadratic, and higher order Zeeman shifts; transition strengths between bound states; and lifetimes of narrow subradiant states. The physical intuition gained in these experiments applies generally to weakly bound diatomic molecules, and suggests extensive applications in precision measurement and metrology. In addition, we present a detailed analysis of the thermally broadened spectroscopic lineshape of molecules in a non-magic optical lattice trap, showing how such lineshapes can be used to directly determine the temperature of atoms or molecules in situ, addressing a long-standing problem in ultracold physics. Finally, we discuss the measurement of photofragment angular distributions produced by photodissociation, leading to an exploration of quantum-state-resolved ultracold chemistry.

Measurement of Bose-Einstein correlations in e^+e^->W^+W^- events at LEP [rapid communication] L3 Collaboration, P. Achard, O. Adriani, M. Aguilar-Benitez, J. Alcaraz, G. Alemanni, J. Allaby, A. Aloisio, M.G. Alviggi, H. Anderhub, V.P. Andreev, F. Anselmo, A. Arefiev, T. Azemoon, T. Aziz,

NASA Astrophysics Data System (ADS)

Bagnaia, P.; Bajo, A.; Baksay, G.; Baksay, L.; Baldew, S. V.; Banerjee, S.; Banerjee, S.; Barczyk, A.; Barillere, R.; Bartalini, P.; Basile, M.; Batalova, N.; Battiston, R.; Bay, A.; Becattini, F.; Becker, U.; Behner, F.; Bellucci, L.; Berbeco, R.; Berdugo, J.; Berges, P.; Bertucci, B.; Betev, B. L.; Biasini, M.; Biglietti, M.; Biland, A.; Blaising, J. J.; Blyth, S. C.; Bobbink, G. J.; Bohm, A.; Boldizsar, L.; Borgia, B.; Bottai, S.; Bourilkov, D.; Bourquin, M.; Braccini, S.; Branson, J. G.; Brochu, F.; Burger, J. D.; Burger, W. J.; Cai, X. D.; Capell, M.; Romeo, G. Cara; Carlino, G.; Cartacci, A.; Casaus, J.; Cavallari, F.; Cavallo, N.; Cecchi, C.; Cerrada, M.; Chamizo, M.; Chang, Y. H.; Chemarin, M.; Chen, A.; Chen, G.; Chen, G. M.; Chen, H. F.; Chen, H. S.; Chiefari, G.; Cifarelli, L.; Cindolo, F.; Clare, I.; Clare, R.; Coignet, G.; Colino, N.; Costantini, S.; de la Cruz, B.; Cucciarelli, S.; van Dalen, J. A.; de Asmundis, R.; Deglon, P.; Debreczeni, J.; Degre, A.; Dehmelt, K.; Deiters, K.; della Volpe, D.; Delmeire, E.; Denes, P.; DeNotaristefani, F.; De Salvo, A.; Diemoz, M.; Dierckxsens, M.; Dionisi, C.; Dittmar, M.; Doria, A.; Dova, M. T.; Duchesneau, D.; Echenard, B.; Eline, A.; El Mamouni, H.; Engler, A.; Eppling, F. J.; Ewers, A.; Extermann, P.; Falagan, M. A.; Falciano, S.; Favara, A.; Fay, J.; Fedin, O.; Felcini, M.; Ferguson, T.; Fesefeldt, H.; Fiandrini, E.; Field, J. H.; Filthaut, F.; Fisher, P. H.; Fisher, W.; Fisk, I.; Forconi, G.; Freudenreich, K.; Furetta, C.; Galaktionov, Y.; Ganguli, S. N.; Garcia-Abia, P.; Gataullin, M.; Gentile, S.; Giagu, S.; Gong, Z. F.; Grenier, G.; Grimm, O.; Gruenewald, M. W.; Guida, M.; van Gulik, R.; Gupta, V. K.; Gurtu, A.; Gutay, L. J.; Haas, D.; Hakobyan, R. S.; Hatzifotiadou, D.; Hebbeker, T.; Herve, A.; Hirschfelder, J.; Hofer, H.; Hohlmann, M.; Holzner, G.; Hou, S. R.; Hu, Y.; Jin, B. N.; Jones, L. W.; de Jong, P.; Josa-Mutuberra, I.; Kafer, D.; Kaur, M.; Kienzle-Focacci, M. N.; Kim, J. K.; Kirkby, J.; Kittel, W.; Klimentov, A.; Konig, A. C.; Kopal, M.; Koutsenko, V.; Kraber, M.; Kraemer, R. W.; Krenz, W.; Kruger, A.; Kunin, A.; Ladron de Guevara, P.; Laktineh, I.; Landi, G.; Lebeau, M.; Lebedev, A.; Lebrun, P.; Lecomte, P.; Lecoq, P.; Le Coultre, P.; Le Goff, J. M.; Leiste, R.; Levtchenko, M.; Levtchenko, P.; Li, C.; Likhoded, S.; Lin, C. H.; Lin, W. T.; Linde, F. L.; Lista, L.; Liu, Z. A.; Lohmann, W.; Longo, E.; Lu, Y. S.; Lubelsmeyer, K.; Luci, C.; Luminari, L.; Lustermann, W.; Ma, W. G.; Malgeri, L.; Malinin, A.; Mana, C.; Mangeol, D.; Mans, J.; Martin, J. P.; Marzano, F.; Mazumdar, K.; McNeil, R. R.; Mele, S.; Merola, L.; Meschini, M.; Metzger, W. J.; Mihul, A.; Milcent, H.; Mirabelli, G.; Mnich, J.; Mohanty, G. B.; Muanza, G. S.; Muijs, A. J. M.; Musicar, B.; Musy, M.; Nagy, S.; Natale, S.; Napolitano, M.; Nessi-Tedaldi, F.; Newman, H.; Niessen, T.; Nisati, A.; Nowak, H.; Ofierzynski, R.; Organtini, G.; Palomares, C.; Pandoulas, D.; Paolucci, P.; Paramatti, R.; Passaleva, G.; Patricelli, S.; Paul, T.; Pauluzzi, M.; Paus, C.; Pauss, F.; Pedace, M.; Pensotti, S.; Perret-Gallix, D.; Petersen, B.; Piccolo, D.; Pierella, F.; Pioppi, M.; Piroue, P. A.; Pistolesi, E.; Plyaskin, V.; Pohl, M.; Pojidaev, V.; Pothier, J.; Prokofiev, D. O.; Prokofiev, D.; Quartieri, J.; Rahal-Callot, G.; Rahaman, M. A.; Raics, P.; Raja, N.; Ramelli, R.; Rancoita, P. G.; Ranieri, R.; Raspereza, A.; Razis, P.; Ren, D.; Rescigno, M.; Reucroft, S.; Riemann, S.; Riles, K.; Roe, B. P.; Romero, L.; Rosca, A.; Rosier-Lees, S.; Roth, S.; Rosenbleck, C.; Roux, B.; Rubio, J. A.; Ruggiero, G.; Rykaczewski, H.; Sakharov, A.; Saremi, S.; Sarkar, S.; Salicio, J.; Sanchez, E.; Sanders, M. P.; Schafer, C.; Schegelsky, V.; Schmidt-Kaerst, S.; Schmitz, D.; Schopper, H.; Schotanus, D. J.; Schwering, G.; Sciacca, C.; Servoli, L.; Shevchenko, S.; Shivarov, N.; Shoutko, V.; Shumilov, E.; Shvorob, A.; Siedenburg, T.; Son, D.; Souga, C.; Spillantini, P.; Steuer, M.; Stickland, D. P.; Stoyanov, B.; Straessner, A.; Sudhakar, K.; Sultanov, G.; Sun, L. Z.; Sushkov, S.; Suter, H.; Swain, J. D.; Szillasi, Z.; Tang, X. W.; Tarjan, P.; Tauscher, L.; Taylor, L.; Tellili, B.; Teyssier, D.; Timmermans, C.; Ting, C. C.; Ting, S. M.; Tonwar, S. C.; Toth, J.; Tully, C.; Tung, K. L.; Ulbricht, J.; Valente, E.; Van de Walle, R. T.; Vasquez, R.; Veszpremi, V.; Vesztergombi, G.; Vetlitsky, I.; Vicinanza, D.; Viertel, G.; Villa, S.; Vivargent, M.; Vlachos, S.; Vodopianov, I.; Vogel, H.; Vogt, H.; Vorobiev, I.; Vorobyov, A. A.; Wadhwa, M.; Wallraff, W.; Wang, X. L.; Wang, Z. M.; Weber, M.; Wienemann, P.; Wilkens, H.; Wynhoff, S.; Xia, L.; Xu, Z. Z.; Yamamoto, J.; Yang, B. Z.; Yang, C. G.; Yang, H. J.; Yang, M.; Yeh, S. C.; Zalite, A.; Zalite, Y.; Zhang, Z. P.; Zhao, J.; Zhu, G. Y.; Zhu, R. Y.; Zhuang, H. L.; Zichichi, A.; Zimmermann, B.; Zoller, M.

2002-11-01

Bose-Einstein correlations in W-pair production at LEP are investigated in a data sample of 629 pb^-1 collected by the L3 detector at centre-of-mass energies of 189-209 GeV. Bose-Einstein correlations between pions within a W decay are observed and found to be in good agreement with those in light-quark Z decay. No evidence is found for Bose-Einstein correlations between hadrons coming from different W's in the same event.

Steady state current fluctuations and dynamical control in a nonequilibrium single-site Bose-Hubbard system

NASA Astrophysics Data System (ADS)

Chen, Xu-Min; Wang, Chen; Sun, Ke-Wei

2018-02-01

We investigate nonequilibrium energy transfer in a single-site Bose-Hubbard model coupled to two thermal baths. By including a quantum kinetic equation combined with full counting statistics, we investigate the steady state energy flux and noise power. The influence of the nonlinear Bose-Hubbard interaction on the transfer behaviors is analyzed, and the nonmonotonic features are clearly exhibited. Particularly, in the strong on-site repulsion limit, the results become identical with the nonequilibrium spin-boson model. We also extend the quantum kinetic equation to study the geometric-phase-induced energy pump. An interesting reversal behavior is unraveled by enhancing the Bose-Hubbard repulsion strength.

An experimental toolbox for the generation of cold and ultracold polar molecules

NASA Astrophysics Data System (ADS)

Zeppenfeld, Martin; Gantner, Thomas; Glöckner, Rosa; Ibrügger, Martin; Koller, Manuel; Prehn, Alexander; Wu, Xing; Chervenkov, Sotir; Rempe, Gerhard

2017-01-01

Cold and ultracold molecules enable fascinating applications in quantum science. We present our toolbox of techniques to generate the required molecule ensembles, including buffergas cooling, centrifuge deceleration and optoelectrical Sisyphus cooling. We obtain excellent control over both the motional and internal molecular degrees of freedom, allowing us to aim at various applications.

Possible Many-Body Localization in a Long-Lived Finite-Temperature Ultracold Quasineutral Molecular Plasma

NASA Astrophysics Data System (ADS)

Sous, John; Grant, Edward

2018-03-01

We argue that the quenched ultracold plasma presents an experimental platform for studying the quantum many-body physics of disordered systems in the long-time and finite energy-density limits. We consider an experiment that quenches a plasma of nitric oxide to an ultracold system of Rydberg molecules, ions, and electrons that exhibits a long-lived state of arrested relaxation. The qualitative features of this state fail to conform with classical models. Here, we develop a microscopic quantum description for the arrested phase based on an effective many-body spin Hamiltonian that includes both dipole-dipole and van der Waals interactions. This effective model appears to offer a way to envision the essential quantum disordered nonequilibrium physics of this system.

Preparation of a high concentration of lithium-7 atoms in a magneto-optical trap

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zelener, B. B., E-mail: bobozel@mail.ru; Saakyan, S. A.; Sautenkov, V. A.

2014-11-15

This study is aimed at obtaining high concentration of optically cooled lithium-7 atoms for preparing strongly interacting ultracold plasma and Rydberg matter. A special setup has been constructed, in which two high-power semiconductor lasers are used to cool lithium-7 atoms in a magneto-optical trap. At an optimum detuning of the cooling laser frequency and a magnetic field gradient of 35 G/cm, the concentration of ultracold lithium-7 atoms reaches about 10{sup 11} cm{sup −3}. Additional independent information about the concentration and number of ultracold lithium-7 atoms on different sublevels of the ground state was obtained by using of an additional probingmore » laser.« less

Parton Theory of Magnetic Polarons: Mesonic Resonances and Signatures in Dynamics

NASA Astrophysics Data System (ADS)

Grusdt, F.; Kánasz-Nagy, M.; Bohrdt, A.; Chiu, C. S.; Ji, G.; Greiner, M.; Greif, D.; Demler, E.

2018-01-01

When a mobile hole is moving in an antiferromagnet it distorts the surrounding Néel order and forms a magnetic polaron. Such interplay between hole motion and antiferromagnetism is believed to be at the heart of high-temperature superconductivity in cuprates. In this article, we study a single hole described by the t -Jz model with Ising interactions between the spins in two dimensions. This situation can be experimentally realized in quantum gas microscopes with Mott insulators of Rydberg-dressed bosons or fermions, or using polar molecules. We work at strong couplings, where hole hopping is much larger than couplings between the spins. In this regime we find strong theoretical evidence that magnetic polarons can be understood as bound states of two partons, a spinon and a holon carrying spin and charge quantum numbers, respectively. Starting from first principles, we introduce a microscopic parton description which is benchmarked by comparison with results from advanced numerical simulations. Using this parton theory, we predict a series of excited states that are invisible in the spectral function and correspond to rotational excitations of the spinon-holon pair. This is reminiscent of mesonic resonances observed in high-energy physics, which can be understood as rotating quark-antiquark pairs carrying orbital angular momentum. Moreover, we apply the strong-coupling parton theory to study far-from-equilibrium dynamics of magnetic polarons observable in current experiments with ultracold atoms. Our work supports earlier ideas that partons in a confining phase of matter represent a useful paradigm in condensed-matter physics and in the context of high-temperature superconductivity in particular. While direct observations of spinons and holons in real space are impossible in traditional solid-state experiments, quantum gas microscopes provide a new experimental toolbox. We show that, using this platform, direct observations of partons in and out of equilibrium are now possible. Extensions of our approach to the t -J model are also discussed. Our predictions in this case are relevant to current experiments with quantum gas microscopes for ultracold atoms.

The Evolution of Hyperedge Cardinalities and Bose-Einstein Condensation in Hypernetworks.

PubMed

Guo, Jin-Li; Suo, Qi; Shen, Ai-Zhong; Forrest, Jeffrey

2016-09-27

To depict the complex relationship among nodes and the evolving process of a complex system, a Bose-Einstein hypernetwork is proposed in this paper. Based on two basic evolutionary mechanisms, growth and preference jumping, the distribution of hyperedge cardinalities is studied. The Poisson process theory is used to describe the arrival process of new node batches. And, by using the Poisson process theory and a continuity technique, the hypernetwork is analyzed and the characteristic equation of hyperedge cardinalities is obtained. Additionally, an analytical expression for the stationary average hyperedge cardinality distribution is derived by employing the characteristic equation, from which Bose-Einstein condensation in the hypernetwork is obtained. The theoretical analyses in this paper agree with the conducted numerical simulations. This is the first study on the hyperedge cardinality in hypernetworks, where Bose-Einstein condensation can be regarded as a special case of hypernetworks. Moreover, a condensation degree is also discussed with which Bose-Einstein condensation can be classified.

Bose-Einstein condensate in an optical lattice with Raman-assisted two-dimensional spin-orbit coupling

NASA Astrophysics Data System (ADS)

Pan, Jian-Song; Zhang, Wei; Yi, Wei; Guo, Guang-Can

2016-10-01

In a recent experiment (Z. Wu, L. Zhang, W. Sun, X.-T. Xu, B.-Z. Wang, S.-C. Ji, Y. Deng, S. Chen, X.-J. Liu, and J.-W. Pan, arXiv:1511.08170 [cond-mat.quant-gas]), a Raman-assisted two-dimensional spin-orbit coupling has been realized for a Bose-Einstein condensate in an optical lattice potential. In light of this exciting progress, we study in detail key properties of the system. As the Raman lasers inevitably couple atoms to high-lying bands, the behaviors of the system in both the single- and many-particle sectors are significantly affected. In particular, the high-band effects enhance the plane-wave phase and lead to the emergence of "roton" gaps at low Zeeman fields. Furthermore, we identify high-band-induced topological phase boundaries in both the single-particle and the quasiparticle spectra. We then derive an effective two-band model, which captures the high-band physics in the experimentally relevant regime. Our results not only offer valuable insights into the two-dimensional lattice spin-orbit coupling, but also provide a systematic formalism to model high-band effects in lattice systems with Raman-assisted spin-orbit couplings.

Optimized Hypernetted-Chain Solutions for Helium -4 Surfaces and Metal Surfaces

NASA Astrophysics Data System (ADS)

Qian, Guo-Xin

This thesis is a study of inhomogeneous Bose systems such as liquid ('4)He slabs and inhomogeneous Fermi systems such as the electron gas in metal films, at zero temperature. Using a Jastrow-type many-body wavefunction, the ground state energy is expressed by means of Bogoliubov-Born-Green-Kirkwood -Yvon and Hypernetted-Chain techniques. For Bose systems, Euler-Lagrange equations are derived for the one- and two -body functions and systematic approximation methods are physically motivated. It is shown that the optimized variational method includes a self-consistent summation of ladder- and ring-diagrams of conventional many-body theory. For Fermi systems, a linear potential model is adopted to generate the optimized Hartree-Fock basis. Euler-Lagrange equations are derived for the two-body correlations which serve to screen the strong bare Coulomb interaction. The optimization of the pair correlation leads to an expression of correlation energy in which the state averaged RPA part is separated. Numerical applications are presented for the density profile and pair distribution function for both ('4)He surfaces and metal surfaces. Both the bulk and surface energies are calculated in good agreement with experiments.

Direct observation of growth and collapse of a Bose-Einstein condensate with attractive interactions

NASA Astrophysics Data System (ADS)

Gerton, Jordan M.; Strekalov, Dmitry; Prodan, Ionut; Hulet, Randall G.

2000-12-01

Quantum theory predicts that Bose-Einstein condensation of a spatially homogeneous gas with attractive interactions is precluded by a conventional phase transition into either a liquid or solid. When confined to a trap, however, such a condensate can form, provided that its occupation number does not exceed a limiting value. The stability limit is determined by a balance between the self-attractive forces and a repulsion that arises from position-momentum uncertainty under conditions of spatial confinement. Near the stability limit, self-attraction can overwhelm the repulsion, causing the condensate to collapse. Growth of the condensate is therefore punctuated by intermittent collapses that are triggered by either macroscopic quantum tunnelling or thermal fluctuation. Previous observations of growth and collapse dynamics have been hampered by the stochastic nature of these mechanisms. Here we report direct observations of the growth and subsequent collapse of a 7Li condensate with attractive interactions, using phase-contrast imaging. The success of the measurement lies in our ability to reduce the stochasticity in the dynamics by controlling the initial number of condensate atoms using a two-photon transition to a diatomic molecular state.

Quantum droplets of light in the presence of synthetic magnetic fields

NASA Astrophysics Data System (ADS)

Wilson, Kali; Westerberg, Niclas; Valiente, Manuel; Duncan, Callum; Wright, Ewan; Ohberg, Patrik; Faccio, Daniele

2017-04-01

Recently, quantum droplets have been demonstrated in dipolar Bose-Einstein condensates, where the long range (nonlocal) attractive interaction is counterbalanced by a local repulsive interaction. In this work, we investigate the formation of quantum droplets in a two-dimensional nonlocal fluid of light. Fluids of light allow us to control the geometry of the system, and thus introduce vorticity which in turn creates an artificial magnetic field for the quantum droplet. In a quantum fluid of light, the photons comprising the fluid are treated as a gas of interacting Bose-particles, where the nonlocal interaction comes from the nonlinearity inherent in the material, in our case an attractive third-order thermo-optical nonlinearity. In contrast to matter-wave droplets, photon fluid droplets are not stabilised by local particle-particle scattering, but from the quantum pressure itself, i.e., a balance between diffraction and the nonlocal nonlinearity. We will present a numerical and analytical investigation of the ground state of these droplets and of their subsequent dynamics under the influence of a self-induced artificial magnetic field, and discuss experimental work with the possibility to include artificial gauge interactions between droplets.

Cosmological perturbations during the Bose-Einstein condensation of dark matter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Freitas, R.C.; Gonçalves, S.V.B., E-mail: rodolfo.camargo@pq.cnpq.br, E-mail: sergio.vitorino@pq.cnpq.br

In the present work, we analyze the evolution of the scalar and tensorial perturbations and the quantities relevant for the physical description of the Universe, as the density contrast of the scalar perturbations and the gravitational waves energy density during the Bose-Einstein condensation of dark matter. The behavior of these parameters during the Bose-Einstein phase transition of dark matter is analyzed in details. To study the cosmological dynamics and evolution of scalar and tensorial perturbations in a Universe with and without cosmological constant we use both analytical and numerical methods. The Bose-Einstein phase transition modifies the evolution of gravitational wavesmore » of cosmological origin, as well as the process of large-scale structure formation.« less

Above-threshold scattering about a Feshbach resonance for ultracold atoms in an optical collider.

PubMed

Horvath, Milena S J; Thomas, Ryan; Tiesinga, Eite; Deb, Amita B; Kjærgaard, Niels

2017-09-06

Ultracold atomic gases have realized numerous paradigms of condensed matter physics, where control over interactions has crucially been afforded by tunable Feshbach resonances. So far, the characterization of these Feshbach resonances has almost exclusively relied on experiments in the threshold regime near zero energy. Here, we use a laser-based collider to probe a narrow magnetic Feshbach resonance of rubidium above threshold. By measuring the overall atomic loss from colliding clouds as a function of magnetic field, we track the energy-dependent resonance position. At higher energy, our collider scheme broadens the loss feature, making the identification of the narrow resonance challenging. However, we observe that the collisions give rise to shifts in the center-of-mass positions of outgoing clouds. The shifts cross zero at the resonance and this allows us to accurately determine its location well above threshold. Our inferred resonance positions are in excellent agreement with theory.Studies on energy-dependent scattering of ultracold atoms were previously carried out near zero collision energies. Here, the authors observe a magnetic Feshbach resonance in ultracold Rb collisions for above-threshold energies and their method can also be used to detect higher partial wave resonances.

Magnetoassociation of KRb Feshbach molecules

NASA Astrophysics Data System (ADS)

Cumby, Tyler; Perreault, John; Shewmon, Ruth; Jin, Deborah

2010-03-01

I will discuss experiments in which we study the creation of ^40K^87Rb Feshbach molecules via magnetoassociation. We measure the molecule number as a function of the magnetic-field sweep rate through the interspecies Feshbach resonance and explore the dependence of association on the initial atom gas conditions. This study of the Feshbach molecule creation process may be relevant to the production of ultracold polar molecules, where magnetoassociated Feshbach molecules can be a crucial first step [1].[4pt] [1] K.-K. Ni, S. Ospelkaus, M. H. G. de Miranda, A. Peer, B. Neyenhuis, J. J. Zirbel, S. Kotochigova, P. S. Julienne, D. S. Jin, and J. Ye, Science, 2008, 322, 231- 235.

Magnetoassociation of KRb Feshbach molecules

NASA Astrophysics Data System (ADS)

Cumby, Tyler; Perreault, John; Shewmon, Ruth; Jin, Deborah

2010-03-01

I will discuss experiments in which we study the creation of ^40K^87Rb Feshbach molecules via magnetoassociation. We measure the molecule number as a function of the magnetic-field sweep rate through the interspecies Feshbach resonance and explore the dependence of association on the initial atom gas conditions. This study of the Feshbach molecule creation process may be relevant to the production of ultracold polar molecules, where magnetoassociated Feshbach molecules can be a crucial first step [1].[4pt] [1] K.-K. Ni, S. Ospelkaus, M. H. G. de Miranda, A. Peer, B. Neyenhuis, J. J. Zirbel, S. Kotochigova, P. S. Julienne, D. S. Jin, and J. Ye, Science, 2008, 322, 231-235.

Observation of optically induced feshbach resonances in collisions of cold atoms

PubMed

Fatemi; Jones; Lett

2000-11-20

We have observed optically induced Feshbach resonances in a cold ( <1 mK) sodium vapor. The optical coupling of the ground and excited-state potentials changes the scattering properties of an ultracold gas in much the same way as recently observed magnetically induced Feshbach resonances, but allows for some experimental conveniences associated with using lasers. The scattering properties can be varied by changing either the intensity or the detuning of a laser tuned near a photoassociation transition to a molecular state in the dimer. In principle this method allows the scattering length of any atomic species to be altered. A simple model is used to fit the dispersive resonance line shapes.

A new apparatus for studies of quantized vortex dynamics in dilute-gas Bose-Einstein condensates

NASA Astrophysics Data System (ADS)

Newman, Zachary L.

The presence of quantized vortices and a high level of control over trap geometries and other system parameters make dilute-gas Bose-Einstein condensates (BECs) a natural environment for studies of vortex dynamics and quantum turbulence in superfluids, primary interests of the BEC group at the University of Arizona. Such research may lead to deeper understanding of the nature of quantum fluid dynamics and far-from-equilbrium phenomena. Despite the importance of quantized vortex dynamics in the fields of superfluidity, superconductivity and quantum turbulence, direct imaging of vortices in trapped BECs remains a significant technical challenge. This is primarily due to the small size of the vortex core in a trapped gas, which is typically a few hundred nanometers in diameter. In this dissertation I present the design and construction of a new 87Rb BEC apparatus with the goal of studying vortex dynamics in trapped BECs. The heart of the apparatus is a compact vacuum chamber with a custom, all-glass science cell designed to accommodate the use of commercial high-numerical-aperture microscope objectives for in situ imaging of vortices. The designs for the new system are, in part, based on prior work in our group on in situ imaging of vortices. Here I review aspects of our prior work and discuss some of the successes and limitations that are relevant to the new apparatus. The bulk of the thesis is used to described the major subsystems of the new apparatus which include the vacuum chamber, the laser systems, the magnetic transfer system and the final magnetic trap for the atoms. Finally, I demonstrate the creation of a BEC of ˜ 2 x 106 87Rb atoms in our new system and show that the BEC can be transferred into a weak, spherical, magnetic trap with a well defined magnetic field axis that may be useful for future vortex imaging studies.

Nonequilibrium Bose-Einstein condensation of hot magnons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vannucchi, Fabio Stucchi; Vasconcellos, Aurea Rosas; Luzzi, Roberto

We present an analysis of the emergence of a nonequilibrium Bose-Einstein-type condensation of magnons in radio-frequency pumped magnetic thin films, which has recently been experimentally observed. A complete description of all the nonequilibrium processes involved is given. It is demonstrated that the phenomenon is another example of the emergence of Bose-Einstein-type condensation in nonequilibrium many-boson systems embedded in a thermal bath, a phenomenon evidenced decades ago by the renowned late Herbert Froehlich.

Extended Bose-Hubbard model with dipolar and contact interactions

NASA Astrophysics Data System (ADS)

Biedroń, Krzysztof; Łącki, Mateusz; Zakrzewski, Jakub

2018-06-01

We study the phase diagram of the one-dimensional boson gas trapped inside an optical lattice with contact and dipolar interaction, taking into account next-nearest terms for both tunneling and interaction. Using the density-matrix renormalization group, we calculate how the locations of phase transitions change with increasing dipolar interaction strength for average density ρ =1 . Furthermore, we show the emergence of pair-correlated phases for a large dipolar interaction strength and ρ ≥2 , including a supersolid phase with an incommensurate density wave ordering manifesting the corresponding spontaneous breaking of the translational symmetry.

UHV-compatible magnetic material for atom optics

NASA Astrophysics Data System (ADS)

Hopkins, S. A.; Hinds, E. A.; Boshier, M. G.

Magnetic videotape is of great interest for trapping and guiding cold atomic vapors, but was hitherto considered unsuitable for manipulating Bose-Einstein condensates (BEC) because of the presumed evolution of gas under vacuum. We have studied the outgassing in vacuum of the most promising tape, Ampex 398 Betacam SP. We find that after cleaning in ethanol and baking for 200 h at 100 °C the magnetic patterns are undisturbed and the outgassing is remarkably small: 4×10-10 Torrls-1cm-2, due mostly to hydrogen. This makes the tape exceedingly attractive for manipulation of BEC.

Statistical mechanics based on fractional classical and quantum mechanics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Korichi, Z.; Meftah, M. T., E-mail: mewalid@yahoo.com

2014-03-15

The purpose of this work is to study some problems in statistical mechanics based on the fractional classical and quantum mechanics. At first stage we have presented the thermodynamical properties of the classical ideal gas and the system of N classical oscillators. In both cases, the Hamiltonian contains fractional exponents of the phase space (position and momentum). At the second stage, in the context of the fractional quantum mechanics, we have calculated the thermodynamical properties for the black body radiation, studied the Bose-Einstein statistics with the related problem of the condensation and the Fermi-Dirac statistics.

Bose-Einstein Condensation and Bose Glasses in an S = 1 Organo-metallic quantum magnet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zapf, Vivien

2012-06-01

I will speak about Bose-Einstein condensation (BEC) in quantum magnets, in particular the compound NiCl2-4SC(NH2)2. Here a magnetic field-induced quantum phase transition to XY antiferromagnetism can be mapped onto BEC of the spins. The tuning parameter for BEC transition is the magnetic field rather than the temperature. Some interesting phenomena arise, for example the fact that the mass of the bosons that condense can be strongly renormalized by quantum fluctuations. I will discuss the utility of this mapping for both understanding the nature of the quantum magnetism and testing the thermodynamic limit of Bose-Einstein Condensation. Furthermore we can dope themore » system in a clean and controlled way to create the long sought-after Bose Glass transition, which is the bosonic analogy of Anderson localization. I will present experiments and simulations showing evidence for a new scaling exponent, which finally makes contact between theory and experiments. Thus we take a small step towards the difficult problem of understanding the effect of disorder on bosonic wave functions.« less

Analysis of the Alkali Metal Diatomic Spectra; Using molecular beams and ultracold molecules

NASA Astrophysics Data System (ADS)

Kim, Jin-Tae

2014-12-01

This ebook illustrates the complementarity of molecular beam (MB) spectra and ultracold molecule (UM) spectra in unraveling the complex electronic spectra of diatomic alkali metal molecules, using KRb as a prime example. Researchers interested in molecular spectroscopy, whether physicist, chemist, or engineer, may find this ebook helpful and may be able to apply similar ideas to their molecules of interest.

Nicholas Metropolis Award for Outstanding Doctoral Thesis Work in Computational Physics: Quantum many-body physics of ultracold molecules in optical lattices: models and simulation methods

NASA Astrophysics Data System (ADS)

Wall, Michael

2014-03-01

Experimental progress in generating and manipulating synthetic quantum systems, such as ultracold atoms and molecules in optical lattices, has revolutionized our understanding of quantum many-body phenomena and posed new challenges for modern numerical techniques. Ultracold molecules, in particular, feature long-range dipole-dipole interactions and a complex and selectively accessible internal structure of rotational and hyperfine states, leading to many-body models with long range interactions and many internal degrees of freedom. Additionally, the many-body physics of ultracold molecules is often probed far from equilibrium, and so algorithms which simulate quantum many-body dynamics are essential. Numerical methods which are to have significant impact in the design and understanding of such synthetic quantum materials must be able to adapt to a variety of different interactions, physical degrees of freedom, and out-of-equilibrium dynamical protocols. Matrix product state (MPS)-based methods, such as the density-matrix renormalization group (DMRG), have become the de facto standard for strongly interacting low-dimensional systems. Moreover, the flexibility of MPS-based methods makes them ideally suited both to generic, open source implementation as well as to studies of the quantum many-body dynamics of ultracold molecules. After introducing MPSs and variational algorithms using MPSs generally, I will discuss my own research using MPSs for many-body dynamics of long-range interacting systems. In addition, I will describe two open source implementations of MPS-based algorithms in which I was involved, as well as educational materials designed to help undergraduates and graduates perform research in computational quantum many-body physics using a variety of numerical methods including exact diagonalization and static and dynamic variational MPS methods. Finally, I will mention present research on ultracold molecules in optical lattices, such as the exploration of many-body physics with polyatomic molecules, and the next generation of open source matrix product state codes. This work was performed in the research group of Prof. Lincoln D. Carr.

Bose-Einstein correlations of same-sign charged pions in the forward region in pp collisions at √{s}=7 TeV

NASA Astrophysics Data System (ADS)

Aaij, R.; Adeva, B.; Adinolfi, M.; Ajaltouni, Z.; Akar, S.; Albrecht, J.; Alessio, F.; Alexander, M.; Alfonso Albero, A.; Ali, S.; Alkhazov, G.; Alvarez Cartelle, P.; Alves, A. A.; Amato, S.; Amerio, S.; Amhis, Y.; An, L.; Anderlini, L.; Andreassi, G.; Andreotti, M.; Andrews, J. E.; Appleby, R. B.; Archilli, F.; d'Argent, P.; Arnau Romeu, J.; Artamonov, A.; Artuso, M.; Aslanides, E.; Auriemma, G.; Baalouch, M.; Babuschkin, I.; Bachmann, S.; Back, J. J.; Badalov, A.; Baesso, C.; Baker, S.; Balagura, V.; Baldini, W.; Baranov, A.; Barlow, R. J.; Barschel, C.; Barsuk, S.; Barter, W.; Baryshnikov, F.; Batozskaya, V.; Battista, V.; Bay, A.; Beaucourt, L.; Beddow, J.; Bedeschi, F.; Bediaga, I.; Beiter, A.; Bel, L. J.; Beliy, N.; Bellee, V.; Belloli, N.; Belous, K.; Belyaev, I.; Ben-Haim, E.; Bencivenni, G.; Benson, S.; Beranek, S.; Berezhnoy, A.; Bernet, R.; Berninghoff, D.; Bertholet, E.; Bertolin, A.; Betancourt, C.; Betti, F.; Bettler, M.-O.; van Beuzekom, M.; Bezshyiko, Ia.; Bifani, S.; Billoir, P.; Birnkraut, A.; Bitadze, A.; Bizzeti, A.; Bjørn, M.; Blake, T.; Blanc, F.; Blouw, J.; Blusk, S.; Bocci, V.; Boettcher, T.; Bondar, A.; Bondar, N.; Bonivento, W.; Bordyuzhin, I.; Borgheresi, A.; Borghi, S.; Borisyak, M.; Borsato, M.; Bossu, F.; Boubdir, M.; Bowcock, T. J. V.; Bowen, E.; Bozzi, C.; Braun, S.; Britton, T.; Brodzicka, J.; Brundu, D.; Buchanan, E.; Burr, C.; Bursche, A.; Buytaert, J.; Byczynski, W.; Cadeddu, S.; Cai, H.; Calabrese, R.; Calladine, R.; Calvi, M.; Calvo Gomez, M.; Camboni, A.; Campana, P.; Campora Perez, D. H.; Capriotti, L.; Carbone, A.; Carboni, G.; Cardinale, R.; Cardini, A.; Carniti, P.; Carson, L.; Carvalho Akiba, K.; Casse, G.; Cassina, L.; Castillo Garcia, L.; Cattaneo, M.; Cavallero, G.; Cenci, R.; Chamont, D.; Charles, M.; Charpentier, Ph.; Chatzikonstantinidis, G.; Chefdeville, M.; Chen, S.; Cheung, S. F.; Chitic, S.-G.; Chobanova, V.; Chrzaszcz, M.; Chubykin, A.; Ciambrone, P.; Cid Vidal, X.; Ciezarek, G.; Clarke, P. E. L.; Clemencic, M.; Cliff, H. V.; Closier, J.; Cogan, J.; Cogneras, E.; Cogoni, V.; Cojocariu, L.; Collins, P.; Colombo, T.; Comerma-Montells, A.; Contu, A.; Cook, A.; Coombs, G.; Coquereau, S.; Corti, G.; Corvo, M.; Costa Sobral, C. M.; Couturier, B.; Cowan, G. A.; Craik, D. C.; Crocombe, A.; Cruz Torres, M.; Currie, R.; D'Ambrosio, C.; Da Cunha Marinho, F.; Dall'Occo, E.; Dalseno, J.; Davis, A.; De Aguiar Francisco, O.; De Capua, S.; De Cian, M.; De Miranda, J. M.; De Paula, L.; De Serio, M.; De Simone, P.; Dean, C. T.; Decamp, D.; Del Buono, L.; Dembinski, H.-P.; Demmer, M.; Dendek, A.; Derkach, D.; Deschamps, O.; Dettori, F.; Dey, B.; Di Canto, A.; Di Nezza, P.; Dijkstra, H.; Dordei, F.; Dorigo, M.; Dosil Suárez, A.; Douglas, L.; Dovbnya, A.; Dreimanis, K.; Dufour, L.; Dujany, G.; Durante, P.; Dzhelyadin, R.; Dziewiecki, M.; Dziurda, A.; Dzyuba, A.; Easo, S.; Ebert, M.; Egede, U.; Egorychev, V.; Eidelman, S.; Eisenhardt, S.; Eitschberger, U.; Ekelhof, R.; Eklund, L.; Ely, S.; Esen, S.; Evans, H. M.; Evans, T.; Falabella, A.; Farley, N.; Farry, S.; Fazzini, D.; Federici, L.; Ferguson, D.; Fernandez, G.; Fernandez Declara, P.; Fernandez Prieto, A.; Ferrari, F.; Ferreira Rodrigues, F.; Ferro-Luzzi, M.; Filippov, S.; Fini, R. A.; Fiore, M.; Fiorini, M.; Firlej, M.; Fitzpatrick, C.; Fiutowski, T.; Fleuret, F.; Fohl, K.; Fontana, M.; Fontanelli, F.; Forshaw, D. C.; Forty, R.; Franco Lima, V.; Frank, M.; Frei, C.; Fu, J.; Funk, W.; Furfaro, E.; Färber, C.; Gabriel, E.; Gallas Torreira, A.; Galli, D.; Gallorini, S.; Gambetta, S.; Gandelman, M.; Gandini, P.; Gao, Y.; Garcia Martin, L. M.; García Pardiñas, J.; Garra Tico, J.; Garrido, L.; Garsed, P. J.; Gascon, D.; Gaspar, C.; Gavardi, L.; Gazzoni, G.; Gerick, D.; Gersabeck, E.; Gersabeck, M.; Gershon, T.; Ghez, Ph.; Gianì, S.; Gibson, V.; Girard, O. G.; Giubega, L.; Gizdov, K.; Gligorov, V. V.; Golubkov, D.; Golutvin, A.; Gomes, A.; Gorelov, I. V.; Gotti, C.; Govorkova, E.; Grabowski, J. P.; Graciani Diaz, R.; Granado Cardoso, L. A.; Graugés, E.; Graverini, E.; Graziani, G.; Grecu, A.; Greim, R.; Griffith, P.; Grillo, L.; Gruber, L.; Gruberg Cazon, B. R.; Grünberg, O.; Gushchin, E.; Guz, Yu.; Gys, T.; Göbel, C.; Hadavizadeh, T.; Hadjivasiliou, C.; Haefeli, G.; Haen, C.; Haines, S. C.; Hamilton, B.; Han, X.; Hancock, T. H.; Hansmann-Menzemer, S.; Harnew, N.; Harnew, S. T.; Harrison, J.; Hasse, C.; Hatch, M.; He, J.; Hecker, M.; Heinicke, K.; Heister, A.; Hennessy, K.; Henrard, P.; Henry, L.; van Herwijnen, E.; Heß, M.; Hicheur, A.; Hill, D.; Hombach, C.; Hopchev, P. H.; Huard, Z. C.; Hulsbergen, W.; Humair, T.; Hushchyn, M.; Hutchcroft, D.; Ibis, P.; Idzik, M.; Ilten, P.; Jacobsson, R.; Jalocha, J.; Jans, E.; Jawahery, A.; Jezabek, M.; Jiang, F.; John, M.; Johnson, D.; Jones, C. R.; Joram, C.; Jost, B.; Jurik, N.; Kandybei, S.; Karacson, M.; Kariuki, J. M.; Karodia, S.; Kazeev, N.; Kecke, M.; Kelsey, M.; Kenzie, M.; Ketel, T.; Khairullin, E.; Khanji, B.; Khurewathanakul, C.; Kirn, T.; Klaver, S.; Klimaszewski, K.; Klimkovich, T.; Koliiev, S.; Kolpin, M.; Komarov, I.; Kopecna, R.; Koppenburg, P.; Kosmyntseva, A.; Kotriakhova, S.; Kozeiha, M.; Kravchuk, L.; Kreps, M.; Krokovny, P.; Kruse, F.; Krzemien, W.; Kucewicz, W.; Kucharczyk, M.; Kudryavtsev, V.; Kuonen, A. K.; Kurek, K.; Kvaratskheliya, T.; Lacarrere, D.; Lafferty, G.; Lai, A.; Lanfranchi, G.; Langenbruch, C.; Latham, T.; Lazzeroni, C.; Le Gac, R.; Leflat, A.; Lefrançois, J.; Lefèvre, R.; Lemaitre, F.; Lemos Cid, E.; Leroy, O.; Lesiak, T.; Leverington, B.; Li, P.-R.; Li, T.; Li, Y.; Li, Z.; Likhomanenko, T.; Lindner, R.; Lionetto, F.; Lisovskyi, V.; Liu, X.; Loh, D.; Loi, A.; Longstaff, I.; Lopes, J. H.; Lucchesi, D.; Lucio Martinez, M.; Luo, H.; Lupato, A.; Luppi, E.; Lupton, O.; Lusiani, A.; Lyu, X.; Machefert, F.; Maciuc, F.; Macko, V.; Mackowiak, P.; Maddrell-Mander, S.; Maev, O.; Maguire, K.; Maisuzenko, D.; Majewski, M. W.; Malde, S.; Malecki, B.; Malinin, A.; Maltsev, T.; Manca, G.; Mancinelli, G.; Manning, P.; Marangotto, D.; Maratas, J.; Marchand, J. F.; Marconi, U.; Marin Benito, C.; Marinangeli, M.; Marino, P.; Marks, J.; Martellotti, G.; Martin, M.; Martinelli, M.; Martinez Santos, D.; Martinez Vidal, F.; Martins Tostes, D.; Massacrier, L. M.; Massafferri, A.; Matev, R.; Mathad, A.; Mathe, Z.; Matteuzzi, C.; Mauri, A.; Maurice, E.; Maurin, B.; Mazurov, A.; McCann, M.; McNab, A.; McNulty, R.; Mead, J. V.; Meadows, B.; Meaux, C.; Meier, F.; Meinert, N.; Melnychuk, D.; Merk, M.; Merli, A.; Michielin, E.; Milanes, D. A.; Millard, E.; Minard, M.-N.; Minzoni, L.; Mitzel, D. S.; Mogini, A.; Molina Rodriguez, J.; Mombächer, T.; Monroy, I. A.; Monteil, S.; Morandin, M.; Morello, M. J.; Morgunova, O.; Moron, J.; Morris, A. B.; Mountain, R.; Muheim, F.; Mulder, M.; Müller, D.; Müller, J.; Müller, K.; Müller, V.; Naik, P.; Nakada, T.; Nandakumar, R.; Nandi, A.; Nasteva, I.; Needham, M.; Neri, N.; Neubert, S.; Neufeld, N.; Neuner, M.; Nguyen, T. D.; Nguyen-Mau, C.; Nieswand, S.; Niet, R.; Nikitin, N.; Nikodem, T.; Nogay, A.; O'Hanlon, D. P.; Oblakowska-Mucha, A.; Obraztsov, V.; Ogilvy, S.; Oldeman, R.; Onderwater, C. J. G.; Ossowska, A.; Otalora Goicochea, J. M.; Owen, P.; Oyanguren, A.; Pais, P. R.; Palano, A.; Palutan, M.; Papanestis, A.; Pappagallo, M.; Pappalardo, L. L.; Parker, W.; Parkes, C.; Passaleva, G.; Pastore, A.; Patel, M.; Patrignani, C.; Pearce, A.; Pellegrino, A.; Penso, G.; Pepe Altarelli, M.; Perazzini, S.; Perret, P.; Pescatore, L.; Petridis, K.; Petrolini, A.; Petrov, A.; Petruzzo, M.; Picatoste Olloqui, E.; Pietrzyk, B.; Pikies, M.; Pinci, D.; Pisani, F.; Pistone, A.; Piucci, A.; Placinta, V.; Playfer, S.; Plo Casasus, M.; Polci, F.; Poli Lener, M.; Poluektov, A.; Polyakov, I.; Polycarpo, E.; Pomery, G. J.; Ponce, S.; Popov, A.; Popov, D.; Poslavskii, S.; Potterat, C.; Price, E.; Prisciandaro, J.; Prouve, C.; Pugatch, V.; Puig Navarro, A.; Pullen, H.; Punzi, G.; Qian, W.; Quagliani, R.; Quintana, B.; Rachwal, B.; Rademacker, J. H.; Rama, M.; Ramos Pernas, M.; Rangel, M. S.; Raniuk, I.; Ratnikov, F.; Raven, G.; Ravonel Salzgeber, M.; Reboud, M.; Redi, F.; Reichert, S.; dos Reis, A. C.; Remon Alepuz, C.; Renaudin, V.; Ricciardi, S.; Richards, S.; Rihl, M.; Rinnert, K.; Rives Molina, V.; Robbe, P.; Robert, A.; Rodrigues, A. B.; Rodrigues, E.; Rodriguez Lopez, J. A.; Rodriguez Perez, P.; Rogozhnikov, A.; Roiser, S.; Rollings, A.; Romanovskiy, V.; Romero Vidal, A.; Ronayne, J. W.; Rotondo, M.; Rudolph, M. S.; Ruf, T.; Ruiz Valls, P.; Ruiz Vidal, J.; Saborido Silva, J. J.; Sadykhov, E.; Sagidova, N.; Saitta, B.; Salustino Guimaraes, V.; Sanchez Mayordomo, C.; Sanmartin Sedes, B.; Santacesaria, R.; Santamarina Rios, C.; Santimaria, M.; Santovetti, E.; Sarpis, G.; Sarti, A.; Satriano, C.; Satta, A.; Saunders, D. M.; Savrina, D.; Schael, S.; Schellenberg, M.; Schiller, M.; Schindler, H.; Schlupp, M.; Schmelling, M.; Schmelzer, T.; Schmidt, B.; Schneider, O.; Schopper, A.; Schreiner, H. F.; Schubert, K.; Schubiger, M.; Schune, M.-H.; Schwemmer, R.; Sciascia, B.; Sciubba, A.; Semennikov, A.; Sepulveda, E. S.; Sergi, A.; Serra, N.; Serrano, J.; Sestini, L.; Seyfert, P.; Shapkin, M.; Shapoval, I.; Shcheglov, Y.; Shears, T.; Shekhtman, L.; Shevchenko, V.; Siddi, B. G.; Silva Coutinho, R.; Silva de Oliveira, L.; Simi, G.; Simone, S.; Sirendi, M.; Skidmore, N.; Skwarnicki, T.; Smith, E.; Smith, I. T.; Smith, J.; Smith, M.; Soares Lavra, l.; Sokoloff, M. D.; Soler, F. J. P.; Souza De Paula, B.; Spaan, B.; Spradlin, P.; Sridharan, S.; Stagni, F.; Stahl, M.; Stahl, S.; Stefko, P.; Stefkova, S.; Steinkamp, O.; Stemmle, S.; Stenyakin, O.; Stepanova, M.; Stevens, H.; Stone, S.; Storaci, B.; Stracka, S.; Stramaglia, M. E.; Straticiuc, M.; Straumann, U.; Sun, J.; Sun, L.; Sutcliffe, W.; Swientek, K.; Syropoulos, V.; Szczekowski, M.; Szumlak, T.; Szymanski, M.; T'Jampens, S.; Tayduganov, A.; Tekampe, T.; Tellarini, G.; Teubert, F.; Thomas, E.; van Tilburg, J.; Tilley, M. J.; Tisserand, V.; Tobin, M.; Tolk, S.; Tomassetti, L.; Tonelli, D.; Toriello, F.; Tourinho Jadallah Aoude, R.; Tournefier, E.; Traill, M.; Tran, M. T.; Tresch, M.; Trisovic, A.; Tsaregorodtsev, A.; Tsopelas, P.; Tully, A.; Tuning, N.; Ukleja, A.; Usachov, A.; Ustyuzhanin, A.; Uwer, U.; Vacca, C.; Vagner, A.; Vagnoni, V.; Valassi, A.; Valat, S.; Valenti, G.; Vazquez Gomez, R.; Vazquez Regueiro, P.; Vecchi, S.; van Veghel, M.; Velthuis, J. J.; Veltri, M.; Veneziano, G.; Venkateswaran, A.; Verlage, T. A.; Vernet, M.; Vesterinen, M.; Viana Barbosa, J. V.; Viaud, B.; Vieira, D.; Vieites Diaz, M.; Viemann, H.; Vilasis-Cardona, X.; Vitti, M.; Volkov, V.; Vollhardt, A.; Voneki, B.; Vorobyev, A.; Vorobyev, V.; Voß, C.; de Vries, J. A.; Vázquez Sierra, C.; Waldi, R.; Wallace, C.; Wallace, R.; Walsh, J.; Wang, J.; Ward, D. R.; Wark, H. M.; Watson, N. K.; Websdale, D.; Weiden, A.; Whitehead, M.; Wicht, J.; Wilkinson, G.; Wilkinson, M.; Williams, M.; Williams, M. P.; Williams, M.; Williams, T.; Wilson, F. F.; Wimberley, J.; Winn, M.; Wishahi, J.; Wislicki, W.; Witek, M.; Wormser, G.; Wotton, S. A.; Wraight, K.; Wyllie, K.; Xie, Y.; Xu, Z.; Yang, Z.; Yang, Z.; Yao, Y.; Yin, H.; Yu, J.; Yuan, X.; Yushchenko, O.; Zarebski, K. A.; Zavertyaev, M.; Zhang, L.; Zhang, Y.; Zhelezov, A.; Zheng, Y.; Zhu, X.; Zhukov, V.; Zonneveld, J. B.; Zucchelli, S.

2017-12-01

Bose-Einstein correlations of same-sign charged pions, produced in proton-proton collisions at a 7 TeV centre-of-mass energy, are studied using a data sample collected by the LHCb experiment. The signature for Bose-Einstein correlations is observed in the form of an enhancement of pairs of like-sign charged pions with small four-momentum difference squared. The charged-particle multiplicity dependence of the Bose-Einstein correlation parameters describing the correlation strength and the size of the emitting source is investigated, determining both the correlation radius and the chaoticity parameter. The measured correlation radius is found to increase as a function of increasing charged-particle multiplicity, while the chaoticity parameter is seen to decrease. [Figure not available: see fulltext.

Superfluid and Insulating Phases of Fermion Mixtures in Optical Lattices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Iskin, M.; Sa de Melo, C. A. R.

2007-08-24

The ground state phase diagram of fermion mixtures in optical lattices is analyzed as a function of interaction strength, fermion filling factor, and tunneling parameters. In addition to standard superfluid, phase-separated or coexisting superfluid-excess-fermion phases found in homogeneous or harmonically trapped systems, fermions in optical lattices have several insulating phases, including a molecular Bose-Mott insulator (BMI), a Fermi-Pauli (band) insulator (FPI), a phase-separated BMI-FPI mixture or a Bose-Fermi checkerboard (BFC). The molecular BMI phase is the fermion mixture counterpart of the atomic BMI found in atomic Bose systems, the BFC or BMI-FPI phases exist in Bose-Fermi mixtures, and lastly themore » FPI phase is particular to the Fermi nature of the constituent atoms of the mixture.« less

Frustrated spin chains in strong magnetic field: Dilute two-component Bose gas regime

NASA Astrophysics Data System (ADS)

Kolezhuk, A. K.; Heidrich-Meisner, F.; Greschner, S.; Vekua, T.

2012-02-01

We study the ground state of frustrated spin-S chains in a strong magnetic field in the immediate vicinity of saturation. In strongly frustrated chains, the magnon dispersion has two degenerate minima at inequivalent momenta ±Q, and just below the saturation field the system can be effectively represented as a dilute one-dimensional lattice gas of two species of bosons that correspond to magnons with momenta around ±Q. We present a theory of effective interactions in such a dilute magnon gas that allows us to make quantitative predictions for arbitrary values of the spin. With the help of this method, we are able to establish the magnetic phase diagram of frustrated chains close to saturation and study phase transitions between several nontrivial states, including a two-component Luttinger liquid, a vector chiral phase, and phases with bound magnons. We study those phase transitions numerically and find a good agreement with our analytical predictions.

Numerical solutions of ideal quantum gas dynamical flows governed by semiclassical ellipsoidal-statistical distribution.

PubMed

Yang, Jaw-Yen; Yan, Chih-Yuan; Diaz, Manuel; Huang, Juan-Chen; Li, Zhihui; Zhang, Hanxin

2014-01-08

The ideal quantum gas dynamics as manifested by the semiclassical ellipsoidal-statistical (ES) equilibrium distribution derived in Wu et al. (Wu et al . 2012 Proc. R. Soc. A 468 , 1799-1823 (doi:10.1098/rspa.2011.0673)) is numerically studied for particles of three statistics. This anisotropic ES equilibrium distribution was derived using the maximum entropy principle and conserves the mass, momentum and energy, but differs from the standard Fermi-Dirac or Bose-Einstein distribution. The present numerical method combines the discrete velocity (or momentum) ordinate method in momentum space and the high-resolution shock-capturing method in physical space. A decoding procedure to obtain the necessary parameters for determining the ES distribution is also devised. Computations of two-dimensional Riemann problems are presented, and various contours of the quantities unique to this ES model are illustrated. The main flow features, such as shock waves, expansion waves and slip lines and their complex nonlinear interactions, are depicted and found to be consistent with existing calculations for a classical gas.

Cooling Atomic Gases With Disorder

DOE PAGES

Paiva, Thereza; Khatami, Ehsan; Yang, Shuxiang; ...

2015-12-10

Cold atomic gases have proven capable of emulating a number of fundamental condensed matter phenomena including Bose-Einstein condensation, the Mott transition, Fulde-Ferrell-Larkin-Ovchinnikov pairing, and the quantum Hall effect. Cooling to a low enough temperature to explore magnetism and exotic superconductivity in lattices of fermionic atoms remains a challenge. Here in this paper, we propose a method to produce a low temperature gas by preparing it in a disordered potential and following a constant entropy trajectory to deliver the gas into a nondisordered state which exhibits these incompletely understood phases. We show, using quantum Monte Carlo simulations, that we can approachmore » the Néel temperature of the three-dimensional Hubbard model for experimentally achievable parameters. Recent experimental estimates suggest the randomness required lies in a regime where atom transport and equilibration are still robust.« less

Bose-Fermi mapping and a multibranch spin-chain model for strongly interacting quantum gases in one dimension: Dynamics and collective excitations

NASA Astrophysics Data System (ADS)

Yang, Li; Pu, Han

2016-09-01

We show that the wave function in one spatial sector x1

Fractional superstatistics from a kinetic approach

NASA Astrophysics Data System (ADS)

Ourabah, Kamel; Tribeche, Mouloud

2018-03-01

Through a kinetic approach, in which temperature fluctuations are taken into account, we obtain generalized fractional statistics interpolating between Fermi-Dirac and Bose-Einstein statistics. The latter correspond to the superstatistical analogues of the Polychronakos and Haldane-Wu statistics. The virial coefficients corresponding to these statistics are worked out and compared to those of an ideal two-dimensional anyon gas. It is shown that the obtained statistics reproduce correctly the second and third virial coefficients of an anyon gas. On this basis, a link is established between the statistical parameter and the strength of fluctuations. A further generalization is suggested by allowing the statistical parameter to fluctuate. As a by-product, superstatistics of ewkons, introduced recently to deal with dark energy [Phys. Rev. E 94, 062115 (2016), 10.1103/PhysRevE.94.062115], are also obtained within the same method.

Complex wave fields in the interacting one-dimensional Bose gas

NASA Astrophysics Data System (ADS)

Pietraszewicz, J.; Deuar, P.

2018-05-01

We study the temperature regimes of the one-dimensional interacting gas to determine when the matter wave (c-field) theory is, in fact, correct and usable. The judgment is made by investigating the level of discrepancy in many observables at once in comparison to the exact Yang-Yang theory. We also determine what cutoff maximizes the accuracy of such an approach. Results are given in terms of a bound on accuracy, as well as an optimal cutoff prescription. For a wide range of temperatures the optimal cutoff is independent of density or interaction strength and so its temperature-dependent form is suitable for many cloud shapes and, possibly, basis choices. However, this best global choice is higher in energy than most prior determinations. The high value is needed to obtain the correct kinetic energy, but does not detrimentally affect other observables.

Thermodynamic evidence for the Bose glass transition in twinned YBa 2 Cu 3 O 7 - δ crystals

DOE PAGES

Pérez-Morelo, D. J.; Osquiguil, E.; Kolton, A. B.; ...

2015-07-21

We used a micromechanical torsional o scillator to measure the magnetic response of a twinned YBaBa2Cu3O7-δ single crystal disk near the Bose glass transition. We observe an anomaly in the temperature dependence of the magnetization consistent with the appearance of a magnetic shielding perpendicular to the correlated pinning of the twin boundaries. This effect is related to the thermodynamic transition from the vortex liquid phase to a Bose glass state.

Analysis of Bose system in spin-orbit coupled Bose-Fermi mixture to induce a spin current of fermions

NASA Astrophysics Data System (ADS)

Sakamoto, R.; Ono, Y.; Hatsuda, R.; Shiina, K.; Arahata, E.; Mori, H.

2018-03-01

We found that a spin current of fermions could be induced in spin-orbit coupled Bose-Fermi mixture at zero temperature. Since spatial change of the spin structure of the bosons is necessary to induce the spin current of the fermions, we analyzed the ground state of the bosons in the mixture system, using a variational method. The obtained phase diagram indicated the presence of a bosonic phase that allowed the fermions to have a spin current.

Collisional Cooling of Light Ions by Cotrapped Heavy Atoms.

PubMed

Dutta, Sourav; Sawant, Rahul; Rangwala, S A

2017-03-17

We experimentally demonstrate cooling of trapped ions by collisions with cotrapped, higher-mass neutral atoms. It is shown that the lighter ^{39}K^{+} ions, created by ionizing ^{39}K atoms in a magneto-optical trap (MOT), when trapped in an ion trap and subsequently allowed to cool by collisions with ultracold, heavier ^{85}Rb atoms in a MOT, exhibit a longer trap lifetime than without the localized ^{85}Rb MOT atoms. A similar cooling of trapped ^{85}Rb^{+} ions by ultracold ^{133}Cs atoms in a MOT is also demonstrated in a different experimental configuration to validate this mechanism of ion cooling by localized and centered ultracold neutral atoms. Our results suggest that the cooling of ions by localized cold atoms holds for any mass ratio, thereby enabling studies on a wider class of atom-ion systems irrespective of their masses.

The charge imbalance in ultracold plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Tianxing; Lu, Ronghua, E-mail: lurh@siom.ac.cn; Guo, Li

2016-09-15

Ultracold plasmas are regarded as quasineutral but not strictly neutral. The results of charge imbalance in the expansion of ultracold plasmas are reported. The calculations are performed by a full molecular-dynamics simulation. The details of the electron velocity distributions are calculated without the assumption of electron global thermal equilibrium and Boltzmann distribution. Spontaneous evolutions of the charge imbalance from the initial states with perfect neutrality are given in the simulations. The expansion of outer plasma slows down with the charge imbalance. The influences of plasma size and parameters on the charge imbalance are discussed. The radial profiles of electron temperaturemore » are given for the first time, and the self-similar expansion can still occur even if there is no global thermal equilibrium. The electron disorder induced heating is also found in the simulation.« less

Effects of mode profile on tunneling and traversal of ultracold atoms through vacuum-induced potentials

NASA Astrophysics Data System (ADS)

Badshah, Fazal; Irfan, Muhammad; Qamar, Sajid; Qamar, Shahid

2016-04-01

We consider the resonant interaction of an ultracold two-level atom with an electromagnetic field inside a high-Q micromaser cavity. In particular, we study the tunneling and traversal of ultracold atoms through vacuum-induced potentials for secant hyperbolic square and sinusoidal cavity mode functions. The phase time which may be considered as an appropriate measure of the time required for the atoms to cross the cavity, significantly modifies with the change of cavity mode profile. For example, switching between the sub and superclassical behaviors in phase time can occur due to the mode function. Similarly, negative phase time appears for the transmission of the two-level atoms in both excited and ground states for secant hyperbolic square mode function which is in contrast to the mesa mode case.

Universality and chaoticity in ultracold K+KRb chemical reactions

DOE PAGES

Croft, J. F. E.; Makrides, C.; Li, M.; ...

2017-07-19

A fundamental question in the study of chemical reactions is how reactions proceed at a collision energy close to absolute zero. This question is no longer hypothetical: quantum degenerate gases of atoms and molecules can now be created at temperatures lower than a few tens of nanokelvin. Here we consider the benchmark ultracold reaction between, the most-celebrated ultracold molecule, KRb and K. We map out an accurate ab initio ground-state potential energy surface of the K 2Rb complex in full dimensionality and report numerically-exact quantum-mechanical reaction dynamics. The distribution of rotationally resolved rates is shown to be Poissonian. An analysismore » of the hyperspherical adiabatic potential curves explains this statistical character revealing a chaotic distribution for the short-range collision complex that plays a key role in governing the reaction outcome.« less

Atomtronics: Realizing the behavior of electronic components in ultracold atomic systems

NASA Astrophysics Data System (ADS)

Pepino, Ron

2007-06-01

Atomtronics focuses on creating an analogy of electronic devices and circuits with ultracold atoms. Such an analogy can come from the highly tunable band structure of ultracold neutral atoms trapped in optical lattices. Solely by tuning the parameters of the optical lattice, we demonstrate that conditions can be created that cause atoms in lattices to exhibit the same behavior as electrons moving through solid state media. We present our model and show how the atomtronic diode, field effect transistor, and bipolar junction transistor can all be realized. Our analogs of these fundamental components exhibit precisely-controlled atomic signal amplification, trimming, and switching (on/off) characteristics. In addition, the evolution of dynamics of the superfluid atomic currents within these systems is completely reversible. This implies a possible use of atomtronic systems in the development of quantum computational devices.

Forming a Bose-Einstein Condensate

NASA Image and Video Library

2014-09-26

This sequence of false-color images shows the formation of a Bose-Einstein condensate in the Cold Atom Laboratory prototype at NASA Jet Propulsion Laboratory as the temperature gets progressively closer to absolute zero.

Quantum Engineering of Strongly Correlated Matter with Ultracold Fermi Gases

DTIC Science & Technology

2013-05-01

aim at realizing model systems of strongly correlated, disordered electrons using ultracold fermionic atoms stored in an optical "crystal". The general...theme is to study high-temperature superfluids, Fermi liquids ("metals") and insulators in the presence of disordered impurities whose influence on...Presidential Early Career Award for Science and Education (PECASE). In this program, we aim at realizing model systems of strongly correlated, disordered

Fundamental interactions involving neutrons and neutrinos: reactor-based studies led by Petersburg Nuclear Physics Institute (National Research Centre 'Kurchatov Institute') [PNPI (NRC KI)

NASA Astrophysics Data System (ADS)

Serebrov, A. P.

2015-11-01

Neutrons of very low energy ( ˜ 10-7 eV), commonly known as ultracold, are unique in that they can be stored in material and magnetic traps, thus enhancing methodical opportunities to conduct precision experiments and to probe the fundamentals of physics. One of the central problems of physics, of direct relevance to the formation of the Universe, is the violation of time invariance. Experiments searching for the nonzero neutron electric dipole moment serve as a time invariance test, and the use of ultracold neutrons provides very high measurement precision. Precision neutron lifetime measurements using ultracold neutrons are extremely important for checking ideas on the early formation of the Universe. This paper discusses problems that arise in studies using ultracold neutrons. Also discussed are the currently highly topical problem of sterile neutrinos and the search for reactor antineutrino oscillations at distances of 6-12 meters from the reactor core. The field reviewed is being investigated at multiple facilities globally. The present paper mainly concentrates on the results of PNPI-led studies at WWR-M PNPI (Gatchina), ILL (Grenoble), and SM-3 (Dimitrovgrad) reactors, and also covers the results obtained during preparation for research at the PIK reactor which is under construction.