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1

Accounting for Recoil Effects in Geochronometers: A New Model Approach

NASA Astrophysics Data System (ADS)

A number of geologically important chronometers are affected by, or owe their utility to, the "recoil effect". This effect describes the physical displacement of a nuclide due to energetic nuclear processes such as radioactive alpha decay (as in the case of various parent-daughter pairs in the uranium-series decay chains, and Sm-Nd), as well as neutron irradiation (in the case of the methodology for the 40Ar/39Ar dating method). The broad range of affected geochronometers means that the recoil effect can impact a wide range of dating method applications in the geosciences, including but not limited to: Earth surface processes, paleoclimate, volcanic processes, and cosmochemistry and planetary evolution. In particular, the recoil effect can have a notable impact on the use of fine grains (silt- and clay-sized particles) for geochronometric dating purposes. This is because recoil-induced loss of a nuclide from the surfaces of a grain can create an isotopically-depleted outer rind, and for small grains, this depleted rind can be volumetrically significant. When this recoil loss is measurable and occurs in a known time-dependent fashion, it can usefully serve as the basis for chronometers (such as the U-series comminution age method); in other cases recoil loss from fine particles creates an unwanted deviation from expected isotope values (such as for the Ar-Ar method). To improve both the accuracy and precision of ages inferred from geochronometric systems that involve the recoil of a key nuclide from small domains, it is necessary to quantify the magnitude of the recoil loss of that particular nuclide. It is also necessary to quantitatively describe the effect of geological processes that can alter the outer surface of grains, and hence the isotopically-depleted rind. Here we present a new mathematical and numerical model that includes two main features that enable enhanced accuracy and precision of ages determined from geochronometers. Since the surface area of the dated grain is a major control on the magnitude of recoil loss, the first feature is the ability to calculate recoil effects on isotopic compositions for realistic, complex grain shapes and surface roughnesses. This is useful because natural grains may have irregular shapes that do not conform to simple geometric descriptions. Perhaps more importantly, the surface area over which recoiled nuclides are lost can be significantly underestimated when grain surface roughness is not accounted for, since the recoil distances can be of similar characteristic lengthscales to surface roughness features. The second key feature is the ability to incorporate dynamical geologic processes affecting grain surfaces in natural settings, such as dissolution and crystallization. We describe the model and its main components, and point out implications for the geologically-relevant chronometers mentioned above.

Lee, V. E.; Huber, C.

2012-12-01

2

Charge transport-induced recoil and dissociation in double quantum dots.

Colloidal quantum dots (CQDs) are free-standing nanostructures with chemically tunable electronic properties. This combination of properties offers intriguing new possibilities for nanoelectromechanical devices that were not explored yet. In this work, we consider a new scanning tunneling microscopy setup for measuring ligand-mediated effective interdot forces and for inducing motion of individual CQDs within an array. Theoretical analysis of a double quantum dot structure within this setup reveals for the first time voltage-induced interdot recoil and dissociation with pronounced changes in the current. Considering realistic microscopic parameters, our approach enables correlating the onset of mechanical motion under bias voltage with the effective ligand-mediated binding forces. PMID:25259800

Pozner, Roni; Lifshitz, Efrat; Peskin, Uri

2014-11-12

3

Bursts of Radiation and Recoil Effects in Electromagnetism and Gravitation

The Maxwell field of a charge e which experiences an impulsive acceleration or deceleration is constructed explicitly by subdividing Minkowskian space-time into two halves bounded by a future null-cone and then glueing the halves back together with appropriate matching conditions. The resulting retarded radiation can be viewed as instantaneous electromagnetic bremsstrahlung. If we similarly consider a spherically symmetric, moving gravitating mass, to experience an impulsive deceleration, as viewed by a distant observer, then this is accompanied by the emission of a light-like shell whose total energy measured by this observer is the same as the kinetic energy of the source before it stops. This phenomenon is a recoil effect which may be thought of as a limiting case of a Kinnersley rocket.

C. Barrabès; P. A. Hogan

2000-12-06

4

The effects of large angle plural scattering on heavy ion elastic recoil detection analysis

Heavy ion elastic recoil detection analysis (HIERDA) is becoming widely used to study a range of problems in materials science, however there is no standard methodology for the analysis of HIERDA spectra. Major impediments are the effects of multiple and plural scattering which are very significant, even for quite thin (?100 nm) layers of very heavy elements. To examine the

P. N Johnston; R. D Franich; I. F Bubb; M El Bouanani; D. D. Cohen; N. Dytlewski; R. Siegele

2000-01-01

5

Radiation Recoil Effects on the Dynamical Evolution of Asteroids

NASA Astrophysics Data System (ADS)

Abstract (2,250 Maximum Characters): We present the results of the first simulations that self-consistently model the YORP effect on the spin states of dynamically evolving aggregates. We follow the evolution of aggregate objects computing the sequence of spin states and YORP torques through which they evolve as the changing spin alters their shape, which subsequently changes the YORP torques. Previous analyses of the basic behavior of the YORP effect have led to the idea of the ‘YORP cycle’. However, the rotation rates of asteroids obtained from optical light curves suggest that most asteroids are aggregates and Statler [2009] has shown that the YORP effect has an extreme sensitivity to the topography of asteroids (Icarus 202, 501-513). If the spin-driven reconfiguration leads to a shape of the aggregate that is nearly symmetric, the YORP torques could become negligibly small or even vanish. This would imply a self-limitation in the evolution of the spin state and the objects would not follow the classical YORP cycle. Moreover, subsequent reconfigurations could lead to a random walk making the evolution of the spin state completely stochastic. An extensive and statistical analysis of the simulations is conducted to determine whether or not the spin evolution is stochastic and whether the YORP effect is self-limiting. We aim to identify particular behaviors of aggregate objects under the influence of the YORP effect. We present results of their shape evolution including the types, magnitudes and frequencies of movement and shedding of material. We also identify the common characteristics of those objects that have mass loss episodes and of those that exhibit a similar behavior in their spin state or shape evolutions.

Cotto-Figueroa, Desireé; Statler, T. S.; Richardson, D. C.; Tanga, P.

2013-05-01

6

Radiation Recoil Effects on the Dynamical Evolution of Asteroids

NASA Astrophysics Data System (ADS)

The rotation rate of asteroids obtained from optical lightcurves has given strong evidence to support the idea that most asteroids are aggregates. Numerical simulations of the dynamical evolution of aggregates have assumed a constant YORP torque that continuously spins up the object past the point where mass shedding and possible re-accumulations of the shedded mass occur. As a result, the YORP effect is a preferred candidate for the formation of binary asteroids. However, from the results found by Statler [2009] we know that this scenario is not realistic (Icarus 202, 501-513). The YORP effect has an extreme sensitivity to the topography of the asteroids and a minor change in the surface of an aggregate can stochastically change the YORP torques. Moreover, Holsapple [2010] showed (in the continuum limit) that if an object is spun up and allowed to deform continuously, the deformation increases the moment of inertia sufficiently, such that the increase in the angular momentum results in a decreasing spin rate (Icarus 205, 430-442). We self-consistently model the YORP effect on the spin states of dynamically evolving aggregates. The time scales over which mass reconfiguration occur are much shorter than the time scales over which YORP changes the spin states. If the continuous reconfiguration leads to a shape of the aggregate that is nearly symmetric, the YORP torques could become negligibly small or even vanish. This would imply a self-limitation in the evolution of the spin state due to YORP and the objects would not follow the classical YORP cycle. Moreover, subsequent reconfigurations could lead to a random walk in the YORP torques making the evolution of the spin state completely stochastic. This analysis will let us test whether the YORP acceleration is self-limiting and whether the shape changes interrupt the YORP cycle and make the spin evolution stochastic.

Cotto-Figueroa, Desiree; Statler, T. S.; Richardson, D. C.; Tanga, P.

2012-10-01

7

Quantum effects in electron beam pumped GaAs

Propagation of waves in nano-sized GaAs semiconductor induced by electron beam are investigated. A dispersion relation is derived by using quantum hydrodynamics equations including the electrons and holes quantum recoil effects, exchange-correlation potentials, and degenerate pressures. It is found that the propagating modes are instable and strongly depend on the electron beam parameters, as well as the quantum recoil effects and degenerate pressures. The instability region shrinks with the increase of the semiconductor number density. The instability arises because of the energetic electron beam produces electron-hole pairs, which do not keep in phase with the electrostatic potential arising from the pair plasma.

Yahia, M. E. [Faculty of Engineering, The British University in Egypt (BUE), El-Shorouk City, Cairo (Egypt) [Faculty of Engineering, The British University in Egypt (BUE), El-Shorouk City, Cairo (Egypt); National Institute of Laser Enhanced Sciences (NILES), Cairo University (Egypt); Azzouz, I. M. [National Institute of Laser Enhanced Sciences (NILES), Cairo University (Egypt)] [National Institute of Laser Enhanced Sciences (NILES), Cairo University (Egypt); Moslem, W. M. [Department of Physics, Faculty of Science, Port Said University, Port Said (Egypt)] [Department of Physics, Faculty of Science, Port Said University, Port Said (Egypt)

2013-08-19

8

Quantum radiation reaction effects in multiphoton Compton scattering

Radiation reaction effects in the interaction of an electron and a strong laser field are investigated in the realm of quantum electrodynamics. We identify quantum radiation reaction with the multiple photon recoils experienced by the laser-driven electron due to consecutive incoherent photon emissions. After determining a quantum radiation dominated regime, we demonstrate how in this regime quantum signatures of radiation reaction strongly affect multiphoton Compton scattering spectra and that they could be measurable in principle with presently available laser technology.

A. Di Piazza; K. Z. Hatsagortsyan; C. H. Keitel

2010-11-24

9

Complex formation, rearrangement, and reaction in PhOHÂ¿ Â¿ND3: Vibrational mode effects, recoil that a combina- tion of measuring the effects of reactant vibrational excita- tion and collision energy, together,2 Vibrational effects tend to probe events early along the reaction coordinate, provid- ing insight

Anderson, Scott L.

10

Future metrology standards will be partly based on physical quantities computed from first principles rather than measured. In particular, a new pressure standard can be established if the dynamic polarizability of helium can be determined from theory with an uncertainty smaller than 0.2 ppm. We present calculations of the frequency-dependent part of this quantity including relativistic effects with full account of leading nuclear recoil terms and using highly optimized explicitly correlated basis sets. A particular emphasis is put on uncertainty estimates. At the He-Ne laser wavelength of 632.9908 nm, the computed polarizability value of 1.391 811 41 a.u. has uncertainty of 0.1 ppm that is two orders of magnitude smaller than those of the most accurate polarizability measurements. We also obtained an accurate expansion of the helium refractive index in powers of density.

Piszczatowski, Konrad; Komasa, Jacek; Jeziorski, Bogumil; Szalewicz, Krzysztof

2015-01-01

11

NASA Astrophysics Data System (ADS)

Preferential loss relative to 238U of 234U from rocks into solutions has long been attributed to recoiling alpha-emitting nuclei. Using fission-track activation direct evidence has been obtained for two mechanisms: (1) recoil ejection from grains. (2) release by natural etching of alpha-recoil tracks. Tests of the second mechanism have been done using 239PuO 2 sources to implant 235U as recoiling nuclei. These particles leave similar tracks to the recoils from 238U decay, and the implanted nuclei are chemically the same as the 234U that results in nature. Another virtue of 235U nuclei is their fissionability, which allows them to be sensitively detected by neutron irradiation followed by etching of the induced particle tracks. The 235U nuclei are implanted in a mineral, the mineral is exposed to a solution and both the mineral and the solution are tested for their 235U content. Preferential removal of recoil nuclei has been observed in 6 of 7 natural minerals that have been studied in 24-hour treatments. The increase with time of the fraction of the recoil nuclei that is released has been measured in muscovite. The observations also imply that radon emanation occurs by the same two mechanisms.

Fleischer, Robert L.

1982-11-01

12

Recoil effects of a motional scatterer on single-photon scattering in one dimension

The scattering of a single photon with sufficiently high energy can cause a recoil of a motional scatterer. We study its backaction on the photon's coherent transport in one dimension by modeling the motional scatterer as a two-level system, which is trapped in a harmonic potential. While the reflection spectrum is of a single peak in the Lamb-Dicke limit, multi-peaks due to phonon excitations can be observed in the reflection spectrum as the trap becomes looser or the mass of the two-level system becomes smaller. PMID:24220217

Li, Qiong; Xu, D. Z.; Cai, C. Y.; Sun, C. P.

2013-01-01

13

The quantum Hall liquid is a novel state of matter with profound emergent properties such as fractional charge and statistics. Existence of the quantum Hall effect requires breaking of the time reversal symmetry caused by an external magnetic field. In this work, we predict a quantized spin Hall effect in the absence of any magnetic field, where the intrinsic spin Hall conductance is quantized in units of 2 e/4{pi}. The degenerate quantum Landau levels are created by the spin-orbit coupling in conventional semiconductors in the presence of a strain gradient. This new state of matter has many profound correlated properties described by a topological field theory.

Bernevig, B.Andrei; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

2010-01-15

14

NASA Astrophysics Data System (ADS)

List of contributors; Preface; Part I. Introduction: 1. Quantum biology: introduction Graham R. Fleming and Gregory D. Scholes; 2. Open quantum system approaches to biological systems Alireza Shabani, Masoud Mohseni, Seogjoo Jang, Akihito Ishizaki, Martin Plenio, Patrick Rebentrost, Alàn Aspuru-Guzik, Jianshu Cao, Seth Lloyd and Robert Silbey; 3. Generalized Förster resonance energy transfer Seogjoo Jang, Hoda Hossein-Nejad and Gregory D. Scholes; 4. Multidimensional electronic spectroscopy Tomáš Man?al; Part II. Quantum Effects in Bacterial Photosynthetic Energy Transfer: 5. Structure, function, and quantum dynamics of pigment protein complexes Ioan Kosztin and Klaus Schulten; 6. Direct observation of quantum coherence Gregory S. Engel; 7. Environment-assisted quantum transport Masoud Mohseni, Alàn Aspuru-Guzik, Patrick Rebentrost, Alireza Shabani, Seth Lloyd, Susana F. Huelga and Martin B. Plenio; Part III. Quantum Effects in Higher Organisms and Applications: 8. Excitation energy transfer in higher plants Elisabet Romero, Vladimir I. Novoderezhkin and Rienk van Grondelle; 9. Electron transfer in proteins Spiros S. Skourtis; 10. A chemical compass for bird navigation Ilia A. Solov'yov, Thorsten Ritz, Klaus Schulten and Peter J. Hore; 11. Quantum biology of retinal Klaus Schulten and Shigehiko Hayashi; 12. Quantum vibrational effects on sense of smell A. M. Stoneham, L. Turin, J. C. Brookes and A. P. Horsfield; 13. A perspective on possible manifestations of entanglement in biological systems Hans J. Briegel and Sandu Popescu; 14. Design and applications of bio-inspired quantum materials Mohan Sarovar, Dörthe M. Eisele and K. Birgitta Whaley; 15. Coherent excitons in carbon nanotubes Leonas Valkunas and Darius Abramavicius; Glossary; References; Index.

Mohseni, Masoud; Omar, Yasser; Engel, Gregory S.; Plenio, Martin B.

2014-08-01

15

Recent calculations of gravitational radiation recoil generated during black-hole binary mergers have reopened the possibility that a merged binary can be ejected even from the nucleus of a massive host galaxy. Here we report the first systematic study of gravitational recoil of equal-mass binaries with equal, but counteraligned, spins parallel to the orbital plane. Such an orientation of the spins is expected to maximize the recoil. We find that recoil velocity (which is perpendicular to the orbital plane) varies sinusoidally with the angle that the initial spin directions make with the initial linear momenta of each hole and scales up to a maximum of approximately 4000 km s-1 for maximally rotating holes. Our results show that the amplitude of the recoil velocity can depend sensitively on spin orientations of the black holes prior to merger. PMID:17677894

Campanelli, Manuela; Lousto, Carlos O; Zlochower, Yosef; Merritt, David

2007-06-01

16

Transport of Radioactive Material by Alpha Recoil

The movement of high-specific-activity radioactive particles (i.e., alpha recoil) has been observed and studied since the early 1900s. These studies have been motivated by concerns about containment of radioactivity and the protection of human health. Additionally, studies have investigated the potential advantage of alpha recoil to effect separations of various isotopes. This report provides a review of the observations and results of a number of the studies.

Icenhour, A.S.

2005-05-19

17

NASA Astrophysics Data System (ADS)

Stilbite from Malmberget and Svappavara is part of hydrothermal mineral assemblages occupying regionally occurring open Palaeoproterozoic fractures in northern Sweden. At these locations, stilbite is characterized by Pb rad excess relative to U and by activity ratios of [ 234U]/[ 238U] > 1 and [ 230Th]/[ 238U] > 1. The activity disequilibrium requires a disturbance of the U-Th systematics within the last one million years. Leaching and infiltration experiments on Malmberget stilbite demonstrate: (i) preferential leaching in the order Pb >U >Th and uptake in the order Pb > U, and (ii) isotopic fractionation of U by preferential mobilization of 238U and 235U relative to 234U. Stepwise-leaching further indicates that the bulk of U is hosted in the channel sites of stilbite. The Th-U disequilibrium systematics observed in untreated Malmberget and Svappavara stilbite can be explained by: (1) addition of U with [ 234U]/[ 238U] > 1 from a fluid, or alternatively (2) loss of U from a two-component system, consisting of a component that is "open" or accessible and a component that is "closed" or inaccessible to mobilization. U addition requires a multistage history involving multiple gain or loss of U and/or Pb. In contrast, U loss does not necessarily require multistage processes but can also be explained by preferential removal of 238U (and 235U) relative to recoiled daughter isotopes such as 234U, 230Th, and 206Pb (and 207Pb) during a single event. Such a behavior could be obtained if the recoiled daughter isotopes of channel-sited uranium are implanted into the crystal lattice and, in such a way, become less mobile than their parent isotopes. This case implies an open-system behavior for ions in the channel sites and a closed-system behavior for ions in the silicate framework of stilbite. Each ?-recoil directly or indirectly, i.e., through its recoil cascade, damages the silicate framework. Subsequent (continuous) low-temperature annealing of the damaged stilbite lattice could trap the recoiled daughter isotopes in the repaired crystal lattice or sealed-off channels. Such immobile recoiled material can, in part, represent the "closed" component of the system. This model can account for all observations regarding the Th-U-Pb systematics, including the Th-U disequilibrium systematics, the similarity in Th/U as deduced from Th-U disequilibrium and Pb isotope data, and the excess of radiogenic Pb ( 208Pb-parents also had been multiply recoiled). These two contrasting explanations involve either multistage or multicomponent systems. They do not permit the derivation of an accurate age.

Romer, Rolf L.; Rocholl, Alexander

2004-11-01

18

Gravitational Recoil and Astrophysical Impact

NASA Astrophysics Data System (ADS)

Asymmetric emission of gravitational waves from astrophysical sources leads to a net flux of linear momentum from the source and, by momentum conservation, imparts a gravitational recoil on the emitting source. Numerical relativity simulations have revealed that this effect can lead to astonishingly large kick velocities, so-called superkicks, of several thousand km/s in the inspiral and merger of black-hole binaries. We here discuss the calculation of the recoil in black-hole spacetimes and the astrophysical repercussions of such large kicks, in particular related to the possible displacement or ejection of supermassive black holes from their host galaxies. We also discuss possible mechanisms that would make superkicks less likely to occur in astrophysical binaries and thus explain why most, if not all, galaxies observed in this context appear to harbor a black hole at their center.

Sperhake, Ulrich

19

NASA Astrophysics Data System (ADS)

For the final running period of HERA, a recoil detector was installed at the HERMES experiment to improve measurements of hard exclusive processes in charged-lepton nucleon scattering. Here, deeply virtual Compton scattering is of particular interest as this process provides constraints on generalised parton distributions that give access to the total angular momenta of quarks within the nucleon. The HERMES recoil detector was designed to improve the selection of exclusive events by a direct measurement of the four-momentum of the recoiling particle. It consisted of three components: two layers of double-sided silicon strip sensors inside the HERA beam vacuum, a two-barrel scintillating fibre tracker, and a photon detector. All sub-detectors were located inside a solenoidal magnetic field with a field strength of 1T. The recoil detector was installed in late 2005. After the commissioning of all components was finished in September 2006, it operated stably until the end of data taking at HERA end of June 2007. The present paper gives a brief overview of the physics processes of interest and the general detector design. The recoil detector components, their calibration, the momentum reconstruction of charged particles, and the event selection are described in detail. The paper closes with a summary of the performance of the detection system.

Airapetian, A.; Aschenauer, E. C.; Belostotski, S.; Borisenko, A.; Bowles, J.; Brodski, I.; Bryzgalov, V.; Burns, J.; Capitani, G. P.; Carassiti, V.; Ciullo, G.; Clarkson, A.; Contalbrigo, M.; De Leo, R.; De Sanctis, E.; Diefenthaler, M.; Di Nezza, P.; Düren, M.; Ehrenfried, M.; Guler, H.; Gregor, I. M.; Hartig, M.; Hill, G.; Hoek, M.; Holler, Y.; Hristova, I.; Jo, H. S.; Kaiser, R.; Keri, T.; Kisselev, A.; Krause, B.; Krauss, B.; Lagamba, L.; Lehmann, I.; Lenisa, P.; Lu, S.; Lu, X.-G.; Lumsden, S.; Mahon, D.; Martinez de la Ossa, A.; Murray, M.; Mussgiller, A.; Nowak, W.-D.; Naryshkin, Y.; Osborne, A.; Pappalardo, L. L.; Perez-Benito, R.; Petrov, A.; Pickert, N.; Prahl, V.; Protopopescu, D.; Reinecke, M.; Riedl, C.; Rith, K.; Rosner, G.; Rubacek, L.; Ryckbosch, D.; Salomatin, Y.; Schnell, G.; Seitz, B.; Shearer, C.; Shutov, V.; Statera, M.; Steijger, J. J. M.; Stenzel, H.; Stewart, J.; Stinzing, F.; Trzcinski, A.; Tytgat, M.; Vandenbroucke, A.; Van Haarlem, Y.; Van Hulse, C.; Varanda, M.; Veretennikov, D.; Vilardi, I.; Vikhrov, V.; Vogel, C.; Yaschenko, S.; Ye, Z.; Yu, W.; Zeiler, D.; Zihlmann, B.

2013-05-01

20

Effective Theories of Quantum Cosmology

We introduce two possible ways of defining effective constraints of quantum systems and applied this effective constraint method to models of WDW Quantum Cosmology and Loop Quantum Cosmology. We analyze effective Hamiltonian constraint on both second and third order and calculate Hubble parameter as well as modified Friedmann equation of each model. Then we compare with a special case using coherent state. It shows that this method is reasonable and as before the classical Big Bang singularity is replaced by a quantum bounce in Loop Quantum Cosmology.

Xinquan Wu; Yongge Ma

2012-12-24

21

Quantum Effects in Biological Systems

NASA Astrophysics Data System (ADS)

The debates about the trivial and non-trivial effects in biological systems have drawn much attention during the last decade or so. What might these non-trivial sorts of quantum effects be? There is no consensus so far among the physicists and biologists regarding the meaning of "non-trivial quantum effects". However, there is no doubt about the implications of the challenging research into quantum effects relevant to biology such as coherent excitations of biomolecules and photosynthesis, quantum tunneling of protons, van der Waals forces, ultrafast dynamics through conical intersections, and phonon-assisted electron tunneling as the basis for our sense of smell, environment assisted transport of ions and entanglement in ion channels, role of quantum vacuum in consciousness. Several authors have discussed the non-trivial quantum effects and classified them into four broad categories: (a) Quantum life principle; (b) Quantum computing in the brain; (c) Quantum computing in genetics; and (d) Quantum consciousness. First, I will review the above developments. I will then discuss in detail the ion transport in the ion channel and the relevance of quantum theory in brain function. The ion transport in the ion channel plays a key role in information processing by the brain.

Roy, Sisir

2014-07-01

22

Low Energy Nuclear Recoil Response in Xenon Gas for Low Mass Dark Matter WIMP Search

to the detection of relatively higher mass WIMPs because of detector threshold limits, background effects, or a lack of fundamental understanding of very low energy nuclear recoils (nuclear recoil energies...

Sofka, Clement James

2014-04-16

23

Spin-orbit coupling and quantum spin Hall effect for neutral atoms without spin flips.

We propose a scheme which realizes spin-orbit coupling and the quantum spin Hall effect for neutral atoms in optical lattices without relying on near resonant laser light to couple different spin states. The spin-orbit coupling is created by modifying the motion of atoms in a spin-dependent way by laser recoil. The spin selectivity is provided by Zeeman shifts created with a magnetic field gradient. Alternatively, a quantum spin Hall Hamiltonian can be created by all-optical means using a period-tripling, spin-dependent superlattice. PMID:24329453

Kennedy, Colin J; Siviloglou, Georgios A; Miyake, Hirokazu; Burton, William Cody; Ketterle, Wolfgang

2013-11-27

24

NASA Astrophysics Data System (ADS)

A model is proposed, which takes into account acceleration of powder particles by a force induced by recoil of material vapors from the irradiated region of the particle surface. Results of a numerical analysis of heat and mass transfer in the case of motion of individual stainless steel powder particles in a gas flow and in a light field of laser radiation under conditions of laser cladding are presented. Acceleration of particles is found to depend on their diameter, carrier gas velocity, powder material properties, laser radiation power, and degree of attenuation of the power density in the laser beam in the direction of its action on the substrate. The calculated results are compared with experimental data on light-propulsion acceleration of individual particles (of aluminum, aluminum oxide, and graphite) under the action of pulsed laser radiation.

Kovaleva, I. O.; Kovalev, O. B.

2012-01-01

25

The photodissociations of jet-cooled IBr and Br2 molecules have been investigated using high resolution ion imaging methods, at excitation energies just above the thresholds for forming, respectively, I(2P3\\/2o)+Br(2P3\\/2o) and Br(2P3\\/2o)+Br*(2P1\\/2o) products from parent molecules in their v''=0 levels. For such molecules, we observe in both cases, that fragments with larger recoil velocities have markedly reduced angular anisotropy, whereas those from

Eckart Wrede; Eloy R. Wouters; Marco Beckert; Richard N. Dixon; Michael N. R. Ashfold

2002-01-01

26

We present results of experiments using coincidence methods between visible photons of Rydberg transitions, projectiles and recoil ions arising from the low energy collision of Kr18+ on Kr. For each observed Rydberg transition, we have determined the charge state distributions for both the recoil ions and the projectiles. From these results we have deduced some information on the creation of

S. Martin; A. Denis; Y. Ouerdane; M. Carré

1992-01-01

27

NASA Astrophysics Data System (ADS)

The aim of our investigation is focused on studying the effect of dopant dose loss during annealing treatments on heavily doped surface layers, obtained by recoil implantation of antimony in silicon. We are interested particularly by the increase of sheet resistance consequently to the shallow junctions obtained at the surface of substrate and the contribution of the dopant dose loss phenomenon following the high concentration of impurities at the surface. In this work, we report some quantitative data concerning the dopant loss at the surface of silicon implanted and its dependence with annealing treatments. Electrical measurements associated with Rutherford backscattering (RBS) technical analysis showed interesting values of sheet resistance compared with classical ion implantation and despite dopant dose loss phenomenon.

Mesli, M. N.; Benbahi, B.; Bouafia, H.; Belmekki, M.; Abidri, B.; Hiadsi, S.

2013-08-01

28

The quantum teleportation protocol can be used to probabilistically simulate a quantum circuit with backward-in-time connections. This allows us to analyze some conceptual problems of time travel in the context of physically realizable situations, to realize encrypted measurements of future states for which the decryption key becomes available only after the state is created, and to probabilistically realize a multistage quantum state processing within the time needed to complete only one stage. The probabilistic nature of the process resolves any paradox.

George Svetlichny

2009-02-27

29

The quantum Hall effect in quantum dot systems

NASA Astrophysics Data System (ADS)

It is proposed to use quantum dots in order to increase the temperatures suitable for observation of the integer quantum Hall effect. A simple estimation using Fock-Darwin spectrum of a quantum dot shows that good part of carriers localized in quantum dots generate the intervals of plateaus robust against elevated temperatures. Numerical calculations employing local trigonometric basis and highly efficient kernel polynomial method adopted for computing the Hall conductivity reveal that quantum dots may enhance peak temperature for the effect by an order of magnitude, possibly above 77 K. Requirements to potentials, quality and arrangement of the quantum dots essential for practical realization of such enhancement are indicated. Comparison of our theoretical results with the quantum Hall measurements in InAs quantum dot systems from two experimental groups is also given.

Beltukov, Y. M.; Greshnov, A. A.

2014-12-01

30

Electric Field effects on quantum correlations in semiconductor quantum dots

We study the effect of external electric bias on the quantum correlations in the array of optically excited coupled semiconductor quantum dots. The correlations are characterized by the quantum discord and concurrence and are observed using excitonic qubits. We employ the lower bound of concurrence for thermal density matrix at different temperatures. The effect of the F\\"orster interaction on correlations will be studied. Our theoretical model detects nonvanishing quantum discord when the electric field is on while concurrence dies, ensuring the existence of nonclassical correlations as measured by the quantum discord.

S. Shojaei; M. Mahdian; R. Yousefjani

2012-05-01

31

Electric Field effects on quantum correlations in semiconductor quantum dots

We study the effect of external electric bias on the quantum correlations in the array of optically excited coupled semiconductor quantum dots. The correlations are characterized by the quantum discord and concurrence and are observed using excitonic qubits. We employ the lower bound of concurrence for thermal density matrix at different temperatures. The effect of the F\\"orster interaction on correlations will be studied. Our theoretical model detects nonvanishing quantum discord when the electric field is on while concurrence dies, ensuring the existence of nonclassical correlations as measured by the quantum discord.

Shojaei, S; Yosefjani, R

2012-01-01

32

Effective Gain Measurement in Quantum Cascade Lasers

Effective Gain Measurement in Quantum Cascade Lasers A new method to measure gain in Quantum, PRISM, *BYU Supported by NSF, PRISM #12;Outline Lasers Â The Basics Quantum Cascade Lasers Gain and Loss unchanged http://www.ux1.eiu.edu/~cfadd/1160/Ch29Atm/Laser.html #12;Quantum Cascade Laser Laser Bar Sample

Petta, Jason

33

RELATIVISTIC SUPPRESSION OF BLACK HOLE RECOILS

Numerical-relativity simulations indicate that the black hole produced in a binary merger can recoil with a velocity up to v {sub max} {approx_equal} 4000 km s{sup -1} with respect to the center of mass of the initial binary. This challenges the paradigm that most galaxies form through hierarchical mergers, yet retain supermassive black holes (SBHs) at their centers despite having escape velocities much less than v {sub max}. Interaction with a circumbinary disk can align the binary black hole spins with their orbital angular momentum, reducing the recoil velocity of the final black hole produced in the subsequent merger. However, the effectiveness of this alignment depends on highly uncertain accretion flows near the binary black holes. In this paper, we show that if the spin S {sub 1} of the more massive binary black hole is even partially aligned with the orbital angular momentum L, relativistic spin precession on sub-parsec scales can align the binary black hole spins with each other. This alignment significantly reduces the recoil velocity even in the absence of gas. For example, if the angle between S {sub 1} and L at large separations is 10{sup 0} while the second spin S {sub 2} is isotropically distributed, the spin alignment discussed in this paper reduces the median recoil from 864 km s{sup -1} to 273 km s{sup -1} for maximally spinning black holes with a mass ratio of 9/11. This reduction will greatly increase the fraction of galaxies retaining their SBHs.

Kesden, Michael; Sperhake, Ulrich; Berti, Emanuele [California Institute of Technology, MC 350-17, 1216 E. California Blvd., Pasadena, CA 91125 (United States)

2010-06-01

34

Quantum channels and memory effects

NASA Astrophysics Data System (ADS)

Any physical process can be represented as a quantum channel mapping an initial state to a final state. Hence it can be characterized from the point of view of communication theory, i.e., in terms of its ability to transfer information. Quantum information provides a theoretical framework and the proper mathematical tools to accomplish this. In this context the notion of codes and communication capacities have been introduced by generalizing them from the classical Shannon theory of information transmission and error correction. The underlying assumption of this approach is to consider the channel not as acting on a single system, but on sequences of systems, which, when properly initialized allow one to overcome the noisy effects induced by the physical process under consideration. While most of the work produced so far has been focused on the case in which a given channel transformation acts identically and independently on the various elements of the sequence (memoryless configuration in jargon), correlated error models appear to be a more realistic way to approach the problem. A slightly different, yet conceptually related, notion of correlated errors applies to a single quantum system which evolves continuously in time under the influence of an external disturbance which acts on it in a non-Markovian fashion. This leads to the study of memory effects in quantum channels: a fertile ground where interesting novel phenomena emerge at the intersection of quantum information theory and other branches of physics. A survey is taken of the field of quantum channels theory while also embracing these specific and complex settings.

Caruso, Filippo; Giovannetti, Vittorio; Lupo, Cosmo; Mancini, Stefano

2014-10-01

35

Fragment recoil anisotropies in the photoinitiated decomposition of HNCO M. Zyrianov, Th. Droz NH CO threshold is investigated. The measured recoil anisotropies fall into two distinct groups, velocity, and angular domains. The angular distributions are usually fit with an effective recoil anis

Reisler, Hanna

36

RECOILING SUPERMASSIVE BLACK HOLES IN SPIN-FLIP RADIO GALAXIES

Numerical relativity simulations predict that coalescence of supermassive black hole (SMBH) binaries leads not only to a spin flip but also to a recoiling of the merger remnant SMBHs. In the literature, X-shaped radio sources are popularly suggested to be candidates for SMBH mergers with spin flip of jet-ejecting SMBHs. Here we investigate the spectral and spatial observational signatures of the recoiling SMBHs in radio sources undergoing black hole spin flip. Our results show that SMBHs in most spin-flip radio sources have mass ratio q {approx}> 0.3 with a minimum possible value q{sub min} {approx_equal} 0.05. For major mergers, the remnant SMBHs can get a kick velocity as high as 2100 km s{sup -1} in the direction within an angle {approx}< 40 Degree-Sign relative to the spin axes of remnant SMBHs, implying that recoiling quasars are biased to be with high Doppler-shifted broad emission lines while recoiling radio galaxies are biased to large apparent spatial off-center displacements. We also calculate the distribution functions of line-of-sight velocity and apparent spatial off-center displacements for spin-flip radio sources with different apparent jet reorientation angles. Our results show that the larger the apparent jet reorientation angle is, the larger the Doppler-shifting recoiling velocity and apparent spatial off-center displacement will be. We investigate the effects of recoiling velocity on the dust torus in spin-flip radio sources and suggest that recoiling of SMBHs would lead to 'dust-poor' active galactic nuclei. Finally, we collect a sample of 19 X-shaped radio objects and for each object give the probability of detecting the predicted signatures of recoiling SMBH.

Liu, F. K.; Wang Dong [Department of Astronomy, Peking University, 100871 Beijing (China); Chen Xian, E-mail: fkliu@pku.edu.cn [Kavli Institute for Astronomy and Astrophysics, Peking University, 100871 Beijing (China)

2012-02-20

37

Quantum mechanical effects from deformation theory

We consider deformations of quantum mechanical operators by using the novel construction tool of warped convolutions. The deformation enables us to obtain several quantum mechanical effects where electromagnetic and gravitomagnetic fields play a role. Furthermore, a quantum plane can be defined by using the deformation techniques. This in turn gives an experimentally verifiable effect.

Much, A. [Max-Planck-Institute for Mathematics in the Sciences, 04103 Leipzig, Germany and Institute for Theoretical Physics, University of Leipzig, 04009 Leipzig (Germany)] [Max-Planck-Institute for Mathematics in the Sciences, 04103 Leipzig, Germany and Institute for Theoretical Physics, University of Leipzig, 04009 Leipzig (Germany)

2014-02-15

38

Nuclear quantum effects in water

In this work, a path integral Car-Parrinello molecular dynamics simulation of liquid water is performed. It is found that the inclusion of nuclear quantum effects systematically improves the agreement of first principles simulations of liquid water with experiment. In addition, the proton momentum distribution is computed utilizing a recently developed open path integral molecular dynamics methodology. It is shown that these results are in good agreement with neutron Compton scattering data for liquid water and ice.

Joseph A. Morrone; Roberto Car

2008-03-25

39

Hyperbolic supersymmetric quantum Hall effect

Developing a noncompact version of the supersymmetric Hopf map, we formulate the quantum Hall effect on a superhyperboloid. Based on OSp(1|2) group theoretical methods, we first analyze the one-particle Landau problem, and successively explore the many-body problem where the Laughlin wave function, hard-core pseudopotential Hamiltonian, and topological excitations are derived. It is also shown that the fuzzy superhyperboloid emerges at the lowest Landau level.

Hasebe, Kazuki [Department of General Education, Takuma National College of Technology, Takuma-cho, Mitoyo-city, Kagawa 769-1192 (Japan)

2008-12-15

40

Planck's Quantum-Driven Integer Quantum Hall Effect in Chaos

NASA Astrophysics Data System (ADS)

We find in a canonical chaotic system, the kicked spin-1 /2 rotor, a Planck's quantum(he)-driven phenomenon bearing a close analogy to the integer quantum Hall effect but of chaos origin. Specifically, the rotor's energy growth is unbounded ("metallic" phase) for a discrete set of critical values of he, but otherwise bounded ("insulating" phase). The latter phase is topological and characterized by a quantum number ("quantized Hall conductance"). The number jumps by unity whenever he passes through each critical value as it decreases. Our findings indicate that rich topological quantum phenomena can emerge from chaos.

Chen, Yu; Tian, Chushun

2014-11-01

41

Recoil-induced subradiance in an ultracold atomic gas

Subradiance, i.e., the cooperative inhibition of spontaneous emission by destructive interatomic interference, can be realized in a cold atomic sample confined in a ring cavity and lightened by a two-frequency laser. The atoms, scattering the photons of the two laser fields into the cavity mode, recoil and change their momentum. Under proper conditions the atomic initial momentum state and the first two momentum recoil states form a three-level degenerate cascade. A stationary subradiant state is obtained after the scattered photons have left the cavity, leaving the atoms in a coherent superposition of the three collective momentum states. Both a semiclassical description of the process and the quantum subradiant state with its Wigner function are given. Antibunching, quantum correlations, and entanglement between the atomic modes of the subradiant state are demonstrated.

Cola, M. M.; Bigerni, D.; Piovella, N. [Dipartimento di Fisica, Universita degli Studi di Milano and INFN Sezione di Milano, Via Celoria 16, Milano I-20133 (Italy)

2009-05-15

42

QUANTUM, SPIN AND QED EFFECTS IN PLASMAS

Plasmas are usually described using classical equations. While this is often a good approximation, where are situations when a quantum description is motivated. In this paper we will include several quantum effects, ranging from particle dispersion, which give raise to the so called Bohm potential, to spin effects, and to quantum electrodynamical effects. The later effects appears when the field strength approaches the Schwinger critical field, which may occur in for example astrophysical systems. Examples of how to model such quantum effects will be presented, and the phenomena resulting from these models will be discussed. 1.

G. Brodin; M. Marklund

43

Quantum Zeno Effect in the Measurement Problem

NASA Technical Reports Server (NTRS)

Critically analyzing the so-called quantum Zeno effect in the measurement problem, we show that observation of this effect does not necessarily mean experimental evidence for the naive notion of wave-function collapse by measurement (the simple projection rule). We also examine what kind of limitation the uncertainty relation and others impose on the observation of the quantum Zeno effect.

Namiki, Mikio; Pasaczio, Saverio

1996-01-01

44

Nonlocal Quantum Effects in Cosmology

Since it is commonly believed that the observed large-scale structure of the Universe is an imprint of quantum fluctuations existing at the very early stage of its evolution, it is reasonable to pose the question: Do the effects of quantum nonlocality, which are well established now by the laboratory studies, manifest themselves also in the early Universe? We try to answer this question by utilizing the results of a few experiments, namely, with the superconducting multi-Josephson-junction loops and the ultracold gases in periodic potentials. Employing a close analogy between the above-mentioned setups and the simplest one-dimensional Friedmann-Robertson-Walker cosmological model, we show that the specific nonlocal correlations revealed in the laboratory studies might be of considerable importance also in treating the strongly-nonequilibrium phase transitions of Higgs fields in the early Universe. Particularly, they should substantially reduce the number of topological defects (e.g., domain walls) expected due to independent establishment of the new phases in the remote spatial regions. This gives us a hint for resolving a long-standing problem of the excessive concentration of topological defects, inconsistent with observational constraints. The same effect may be also relevant to the recent problem of the anomalous behavior of cosmic microwave background fluctuations at large angular scales.

Yurii V. Dumin

2014-01-14

45

Effects of Static Imperfections for Quantum Computing

We model the quantum computer hardware as a two-dimensional lattice of qubits with static imperfections, i.e. fluctuations in individual qubit energies and residual short-range inter-qubit couplings. We show that these imperfections can lead to the emergence of quantum chaos and dynamical thermalization also in a quantum computer ideally decoupled from the environment. We discuss their effect on the stability of

Giuliano Benenti; Giulio Casati

2003-01-01

46

Planck's quantum-driven integer quantum Hall effect in chaos

The integer quantum Hall effect (IQHE) and chaos are commonly conceived as being unrelated. Contrary to common wisdoms, we find in a canonical chaotic system, the kicked spin-$1/2$ rotor, a Planck's quantum($h_e$)-driven phenomenon bearing a firm analogy to IQHE but of chaos origin. Specifically, the rotor's energy growth is unbounded ('metallic' phase) for a discrete set of critical $h_e$-values, but otherwise bounded ('insulating' phase). The latter phase is topological in nature and characterized by a quantum number ('quantized Hall conductance'). The number jumps by unity whenever $h_e$ decreases passing through each critical value. Our findings, within the reach of cold-atom experiments, indicate that rich topological quantum phenomena may emerge from chaos.

Yu Chen; Chushun Tian

2014-09-18

47

Thermodynamic anomalous Hall effect: The quantum regime

NASA Astrophysics Data System (ADS)

A quantum statistical description of the anomalous Hall effect is developed within the framework of the previously proposed thermodynamic mechanism of the anomalous Hall effect in weakly magnetic electron systems with spontaneous spin polarization. A qualitative explanation of the physical nature of the thermodynamic mechanism is followed by a general formulation of the quantum theory of the effect, based on accounting for the local-equilibrium currents. The behavior of the magnetic field dependences and quantum magnetic oscillations of the physical parameters characterizing the anomalous Hall effect is discussed.

Okulov, V. I.; Pamyatnykh, E. A.; Lonchakov, A. T.

2014-11-01

48

Mobilization of thorium, radium and radon radionuclides in ground water by successive alpha-recoils

NASA Astrophysics Data System (ADS)

Alpha-recoil is an important way for the mobilization of ?-decay daughters in ground water. The processes of decay and recoil from 238U to 222Rn and from 232Th to 220Rn are successive. The release rates of successive recoils in this study are quantitatively estimated under two extreme conditions: complete absorption; and no adsorption of recoil elements by the porous medium. The recoil probability, recoil embedding and effective surface area are considered during the analysis. The result of this study shows that the recoil supply rates in the porous medium decrease down the decay chains. For the isotopes within the same decay chains, recoil emanation ratios of daugthers to parent are usually greater than 1 under both end-member conditions. This is consistent with the higher daughter to parent ratios observed in the field measurements. It is also found that the emanation ratios of Th, Ra and Rn show little change with the change of porosity in general. Radon emanation is most efficient at 15-20% porosity under the condition of complete adsorption. The calculated radioactivity ratios of daughters to parents from this study can provide a partial explanation for the disequilibrium of radioactivity of daughters relative to parents observed in natural water. Because of the low solubility of thorium, radium and radon, the emanation rates calculated under the condition of complete adsorption are closer to the natural conditions.

Sun, Hongbing; Semkow, Thomas M.

1998-02-01

49

Coherent quantum effects through dispersive bosonic media

The coherent evolution of two qubits mediated by a set of bosonic field modes is investigated. By assuming a specific asymmetric encoding of the quantum states in the internal levels of the qubits, we show that entangling quantum gates can be realized, with high fidelity, even when a large number of mediating modes is involved. The effect of losses and

Ye Saiyun; Yang Zhenbiao; Zheng Shibiao; Alessio Serafini

2010-01-01

50

The Compton effect: Transition to quantum mechanics

The discovery of the Compton effect at the end of 1922 was a decisive event in the transition to the new quantum mechanics of 1925-1926 because it stimulated physicists to examine anew the fundamental problem of the interaction between radiation and matter. I first discuss Albert Einstein's light-quantum hypothesis of 1905 and why physicists greeted it with extreme skepticism, despite

R. H. Stuewer

2000-01-01

51

Recoil Based Fuel Breeding Fuel Structure

Nuclear transmutation reactions are based on the absorption of a smaller particle as neutron, proton, deuteron, alpha, etc. The resulting compound nucleus gets out of its initial lattice mainly by taking the recoil, also with help from its sudden change in chemical properties. The recoil implantation is used in correlation with thin and ultra thin materials mainly for producing radiopharmaceuticals

Liviu Popa-Simil; Liviu

2008-01-01

52

Experimental Observation of Quantum Talbot Effects

NASA Astrophysics Data System (ADS)

We report the first experimental observation of quantum Talbot effects with single photons and entangled photon pairs. Both the first- and second-order quantum Talbot self-images are observed experimentally. They exhibit unique properties, which are different from those produced by coherent and incoherent classical light sources. In particular, our experiments show that the revival distance of two-photon Talbot imaging is twice the usual classical Talbot length and there is no net improvement in the resolution, due to the near-field effect of Fresnel diffraction, which is different from the case of previous proof-of-principle quantum lithography experiments in the far field.

Song, Xin-Bing; Wang, Hai-Bo; Xiong, Jun; Wang, Kaige; Zhang, Xiangdong; Luo, Kai-Hong; Wu, Ling-An

2011-07-01

53

Experimental observation of quantum Talbot effects.

We report the first experimental observation of quantum Talbot effects with single photons and entangled photon pairs. Both the first- and second-order quantum Talbot self-images are observed experimentally. They exhibit unique properties, which are different from those produced by coherent and incoherent classical light sources. In particular, our experiments show that the revival distance of two-photon Talbot imaging is twice the usual classical Talbot length and there is no net improvement in the resolution, due to the near-field effect of Fresnel diffraction, which is different from the case of previous proof-of-principle quantum lithography experiments in the far field. PMID:21838358

Song, Xin-Bing; Wang, Hai-Bo; Xiong, Jun; Wang, Kaige; Zhang, Xiangdong; Luo, Kai-Hong; Wu, Ling-An

2011-07-15

54

Quantum interference effect and electric field domain formation in quantum well infrared April 1995 An observation of quantum interference effect in photocurrent spectra of a weakly coupled, we report on a new observation of a quantum interference effect in the pho- tocurrent spectra

55

Quantum effects on propagation of surface Langmuir oscillations in semi-bounded quantum plasmas

The quantum effects on the propagation of surface Langmuir oscillations are investigated in semi-bounded quantum plasmas. The specular reflection method is employed to obtain the dispersion relation of the surface Langmuir oscillations. The results show that the surface Langmuir oscillations can be propagated due to the quantum effects. It is also shown that the quantum effect enhances the propagation velocity.

In-Seok Chang; Young-Dae Jung

2008-01-01

56

Quantum Computing and Lie Theory Feynman's suggestion that the only effective way to model quantum phe- nomena on a computer would be to build a computer that made use of quantum mechanics was one of the cornerstones of the birth of quantum com- puting. In his later years he studied both classical and quantum

D'Agnolo, Andrea

57

Doppler- and recoil-free laser excitation of Rydberg states via three-photon transitions

Three-photon laser excitation of Rydberg states by three different laser beams can be arranged in a starlike geometry that simultaneously eliminates the recoil effect and Doppler broadening. Our analytical and numerical calculations for a particular laser excitation scheme 5S{sub 1/2}{yields}5P{sub 3/2}{yields}6S{sub 1/2}{yields}nP in Rb atoms have shown that, compared to the one- and two-photon laser excitation, this approach provides much narrower linewidth and longer coherence time for both cold atom samples and hot vapors, if the intermediate one-photon resonances of the three-photon transition are detuned by more than respective single-photon Doppler widths. This method can be used to improve fidelity of Rydberg quantum gates and precision of spectroscopic measurements in Rydberg atoms.

Ryabtsev, I. I.; Beterov, I. I.; Tretyakov, D. B.; Entin, V. M.; Yakshina, E. A. [A. V. Rzhanov Institute of Semiconductor Physics SB RAS, Prospekt Lavrentyeva 13, 630090 Novosibirsk (Russian Federation)

2011-11-15

58

Gas powered fluid gun with recoil mitigation

A gas powered fluid gun for propelling a stream or slug of a fluid at high velocity toward a target. Recoil mitigation is provided that reduces or eliminates the associated recoil forces, with minimal or no backwash. By launching a quantity of water in the opposite direction, net momentum forces are reduced or eliminated. Examples of recoil mitigation devices include a cone for making a conical fluid sheet, a device forming multiple impinging streams of fluid, a cavitating venturi, one or more spinning vanes, or an annular tangential entry/exit.

Grubelich, Mark C; Yonas, Gerold

2013-11-12

59

Retention studies of recoiling daughter nuclides of 225Ac in polymer vesicles.

Alpha radionuclide therapy is steadily gaining importance and a large number of pre-clinical and clinical studies have been carried out. However, due to the recoil effects the daughter recoil atoms, most of which are alpha emitters as well, receive energies that are much higher than the energies of chemical bonds resulting in decoupling of the radionuclide from common targeting agents. Here, we demonstrate that polymer vesicles (i.e. polymersomes) can retain recoiling daughter nuclei based on an experimental study examining the retention of (221)Fr and (213)Bi when encapsulating (225)Ac. PMID:24374072

Wang, G; de Kruijff, R M; Rol, A; Thijssen, L; Mendes, E; Morgenstern, A; Bruchertseifer, F; Stuart, M C A; Wolterbeek, H T; Denkova, A G

2014-02-01

60

Quantum magnetoelectric effect in iron garnet

NASA Astrophysics Data System (ADS)

The magnetoelectric response and its quantum relaxation phenomenon have been investigated for a single crystal of yttrium iron garnet. The electric-dipole moments, built in by excess localized electrons forming Fe2+ sites, never freeze even at the lowest temperature and relax through a quantum tunneling process. Application of magnetic field enhances the dielectric relaxation strength and gives rise to a large magnetocapacitance effect ( ˜13% at 10 K with 0.5 T). We show that this magnetically tunable quantum paraelectricity is associated with the Fe2+ -based magnetoelectric centers in which the electric polarization depends on the magnetization vector via the spin-orbit coupling.

Yamasaki, Yuichi; Kohara, Yuki; Tokura, Yoshinori

2009-10-01

61

Locality and universality of quantum memory effects

NASA Astrophysics Data System (ADS)

The modeling and analysis of the dynamics of complex systems often requires to employ non-Markovian stochastic processes. While there is a clear and well-established mathematical definition for non-Markovianity in the case of classical systems, the extension to the quantum regime recently caused a vivid debate, leading to many different proposals for the characterization and quantification of memory effects in the dynamics of open quantum systems. Here, we derive a mathematical representation for the non-Markovianity measure based on the exchange of information between the open system and its environment, which reveals the locality and universality of non-Markovianity in the quantum state space and substantially simplifies its numerical and experimental determination. We further illustrate the application of this representation by means of an all-optical experiment which allows the measurement of the degree of memory effects in a photonic quantum process with high accuracy.

Liu, B.-H.; Wißmann, S.; Hu, X.-M.; Zhang, C.; Huang, Y.-F.; Li, C.-F.; Guo, G.-C.; Karlsson, A.; Piilo, J.; Breuer, H.-P.

2014-09-01

62

Experimental Observation of Quantum Talbot Effects

We report the first experimental observation of quantum Talbot effects with single photons and entangled photon pairs. Both the first- and second-order quantum Talbot self-images are observed experimentally. They exhibit unique properties, which are different from those produced by coherent and incoherent classical light sources. In particular, our experiments show that the revival distance of two-photon Talbot imaging is twice

Xin-Bing Song; Hai-Bo Wang; Jun Xiong; Kaige Wang; Xiangdong Zhang; Kai-Hong Luo; Ling-An Wu

2011-01-01

63

Coherent quantum effects through dispersive bosonic media

The coherent evolution of two qubits mediated by a set of bosonic field modes is investigated. By assuming a specific asymmetric encoding of the quantum states in the internal levels of the qubits, we show that entangling quantum gates can be realized, with high fidelity, even when a large number of mediating modes is involved. The effect of losses and imperfections on the gates' operation is also considered in detail.

Ye Saiyun [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom); Department of Physics, Fuzhou University, Fuzhou 350002 (China); Yang Zhenbiao; Zheng Shibiao [Department of Physics, Fuzhou University, Fuzhou 350002 (China); Serafini, Alessio [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom)

2010-07-15

64

Classification of macroscopic quantum effects

NASA Astrophysics Data System (ADS)

We review canonical experiments on systems that have pushed the boundary between the quantum and classical worlds towards much larger scales, and discuss their unique features that enable quantum coherence to survive. Because the types of systems differ so widely, we use a case by case approach to identifying the different parameters and criteria that capture their behaviour in a quantum mechanical framework. We find it helpful to categorise systems into three broad classes defined by mass, spatio-temporal coherence, and number of particles. The classes are not mutually exclusive and in fact the properties of some systems fit into several classes. We discuss experiments by turn, starting with interference of massive objects like macromolecules and micro-mechanical resonators, followed by self-interference of single particles in complex molecules, before examining the striking advances made with superconducting qubits. Finally, we propose a theoretical basis for quantifying the macroscopic features of a system to lay the ground for a more systematic comparison of the quantum properties in disparate systems.

Farrow, Tristan; Vedral, Vlatko

2015-02-01

65

Scintillation Response of Liquid Xenon to Low Energy Nuclear Recoils

Liquid Xenon (LXe) is expected to be an excellent target and detector medium to search for dark matter in the form of Weakly Interacting Massive Particles (WIMPs). Knowledge of LXe ionization and scintillation response to low energy nuclear recoils expected from the scattering of WIMPs by Xe nuclei is important for determining the sensitivity of LXe direct detection experiments. Here we report on new measurements of the scintillation yield of Xe recoils with kinetic energy as low as 10 keV. The dependence of the scintillation yield on applied electric field was also measured in the range of 0 to 4 kV/cm. Results are in good agreement with recent theoretical predictions that take into account the effect of biexcitonic collisions in addition to the nuclear quenching effect.

Aprile, E; Majewski, P; Yamashita, M; Hasty, R; Manzur, A; McKinsey, D N

2005-01-01

66

Scintillation Response of Liquid Xenon to Low Energy Nuclear Recoils

Liquid Xenon (LXe) is expected to be an excellent target and detector medium to search for dark matter in the form of Weakly Interacting Massive Particles (WIMPs). Knowledge of LXe ionization and scintillation response to low energy nuclear recoils expected from the scattering of WIMPs by Xe nuclei is important for determining the sensitivity of LXe direct detection experiments. Here we report on new measurements of the scintillation yield of Xe recoils with kinetic energy as low as 10 keV. The dependence of the scintillation yield on applied electric field was also measured in the range of 0 to 4 kV/cm. Results are in good agreement with recent theoretical predictions that take into account the effect of biexcitonic collisions in addition to the nuclear quenching effect.

E. Aprile; K. L. Giboni; P. Majewski; K. Ni; M. Yamashita; R. Hasty; A. Manzur; D. N. McKinsey

2005-03-29

67

Ion scattering and recoiling from liquid surfaces

We have shown that ion beams can be used to probe the surface composition and molecular orientation of liquid surfaces. Time-of-flight analysis of the kinetic energy of scattered inert gas ions and recoil atoms ejected from the surface reveals the identity of atoms in the topmost atomic surface layer of the liquid. In this report we describe the first scattering\\/recoil

Michael Tassotto; Thomas J. Gannon; Philip R. Watson

1997-01-01

68

Matrix effective theories of the fractional quantum Hall effect

The present understanding of nonperturbative ground states in the fractional quantum Hall effect is based on effective theories of the Jain 'composite fermion' excitations. We review the approach based on matrix variables, i.e. D0 branes, originally introduced by Susskind and Polychronakos. We show that the Maxwell-Chern-Simons matrix gauge theory provides a matrix generalization of the quantum Hall effect, where the

Andrea Cappelli; Ivan D. Rodriguez

2009-01-01

69

Effective Pure States for Bulk Quantum Computation

In bulk quantum computation one can manipulate a large number of indistinguishable quantum computers by parallel unitary operations and measure expectation values of certain observables with limited sensitivity. The initial state of each computer in the ensemble is known but not pure. Methods for obtaining effective pure input states by a series of manipulations have been described by Gershenfeld and Chuang (logical labeling) and Cory et al. (spatial averaging) for the case of quantum computation with nuclear magnetic resonance. We give a different technique called temporal averaging. This method is based on classical randomization, requires no ancilla qubits and can be implemented in nuclear magnetic resonance without using gradient fields. We introduce several temporal averaging algorithms suitable for both high temperature and low temperature bulk quantum computing and analyze the signal to noise behavior of each.

Emanuel Knill; Isaac Chuang; Raymond Laflamme

1997-06-24

70

Simulations of Recoiling Massive Black Holes

NASA Astrophysics Data System (ADS)

The coalescence of black hole binaries is a significant source of gravitational wave radiation. The typically asymmetric nature of this emission, which carries linear momentum, can result in the recoil of the black hole remnant with velocities in the range 100 < Vrecoil < 3750 km s-1. The detectability of recoiling massive black holes (MBH) as off-nuclear QSOs is tightly connected with the properties of the host galaxy, which determine the MBH's orbit and fuel reservoir. We present the results of N-body simulations of recoiling MBHs in high-resolution, non-axisymmetric potentials. We find that if the recoil velocities are high enough to reach regions of the galaxy dominated by the generally triaxial dark matter distribution, the return time is significantly extended when compared to a spherical distribution. We also perform simulations of recoiling MBHs traveling in gas merger remnants, where large amounts of gas have been funneled to the central regions, In this case, the MBHs remain within R<1 kpc from the center of the host even for high recoil velocities (Vrecoil = 1200 km s-1) due to the compactness of the remnant galaxy's nuclear disk. We discuss the implications of both scenarios for detectability.

Guedes, Javiera; Madau, Piero; Mayer, Lucio; Kuhlen, Michael; Diemand, Jürg; Zemp, Marcel

2010-05-01

71

Effective Potentials and Quantum Fluid Models: A Thermodynamic Approach

]. As a consequence, quantum mechanical models in device simulation usually treat quantum effects with a do- main model equivalent. Second, it allows us to mix classical and quantum mechanical models in an engineeringEffective Potentials and Quantum Fluid Models: A Thermodynamic Approach C. Gardner , C. Ringhofer

Ringhofer, Christian

72

Quantum metrology and detection of Unruh effect

We study the quantum metrology for a pair of entangled Unruh-Dewitt detectors when one of them is accelerated and coupled to a massless scalar field. Comparing with previous schemes, our model requires only local interaction and avoids the use of cavities in the probe state preparation process. We show that the probe state preparation and the interaction between the accelerated detector and the external field have significant effects on the value of quantum Fisher information, correspondingly pose variable ultimate limit of precision in the estimation of Unruh effect. We find that the precision of the estimation can be improved by a larger effective coupling strength and a longer interaction time. Alternatively, the energy gap of the detector has a range that can provide us a better precision. Thus we may adjust those parameters and attain a higher precision in the estimation. We also find that an extremely high acceleration is not required in the quantum metrology process.

Jieci Wang; Zehua Tian; Jiliang Jing; Heng Fan

2014-10-19

73

Quantum metrology and estimation of Unruh effect.

We study the quantum metrology for a pair of entangled Unruh-Dewitt detectors when one of them is accelerated and coupled to a massless scalar field. Comparing with previous schemes, our model requires only local interaction and avoids the use of cavities in the probe state preparation process. We show that the probe state preparation and the interaction between the accelerated detector and the external field have significant effects on the value of quantum Fisher information, correspondingly pose variable ultimate limit of precision in the estimation of Unruh effect. We find that the precision of the estimation can be improved by a larger effective coupling strength and a longer interaction time. Alternatively, the energy gap of the detector has a range that can provide us a better precision. Thus we may adjust those parameters and attain a higher precision in the estimation. We also find that an extremely high acceleration is not required in the quantum metrology process. PMID:25424772

Wang, Jieci; Tian, Zehua; Jing, Jiliang; Fan, Heng

2014-01-01

74

Measurement of scintillation efficiency for nuclear recoils in liquid argon

The scintillation light yield of liquid argon from nuclear recoils relative to electronic recoils has been measured as a function of recoil energy from 10 keVr up to 250 keVr. The scintillation efficiency, defined as the ratio of the nuclear recoil scintillation response to the electronic recoil response, is 0.25 \\pm 0.01 + 0.01(correlated) above 20 keVr.

D. Gastler; E. Kearns; A. Hime; L. C. Stonehill; S. Seibert; J. Klein; W. H. Lippincott; D. N. McKinsey; J. A. Nikkel

2012-05-08

75

The Compton effect: Transition to quantum mechanics

NASA Astrophysics Data System (ADS)

The discovery of the Compton effect at the end of 1922 was a decisive event in the transition to the new quantum mechanics of 1925-1926 because it stimulated physicists to examine anew the fundamental problem of the interaction between radiation and matter. I first discuss Albert Einstein's light-quantum hypothesis of 1905 and why physicists greeted it with extreme skepticism, despite Robert A. Millikan's confirmation of Einstein's equation of the photoelectric effect in 1915. I then follow in some detail the experimental and theoretical research program that Arthur Holly Compton pursued between 1916 and 1922 at the University of Minnesota, the Westinghouse Lamp Company, the Cavendish Laboratory, and Washington University that culminated in his discovery of the Compton effect. Surprisingly, Compton was not influenced directly by Einstein's light-quantum hypothesis, in contrast to Peter Debye and H.A. Kramers, who discovered the quantum theory of scattering independently. I close by discussing the most significant response to that discovery, the Bohr-Kramers-Slater theory of 1924, its experimental refutation, and its influence on the emerging new quantum mechanics.

Stuewer, R. H.

2000-11-01

76

Recoiling from a Kick in the Head-On Case

NASA Technical Reports Server (NTRS)

Recoil "kicks" induced by gravitational radiation are expected in the inspiral and merger of black holes. Recently the numerical relativity community has begun to measure the significant kicks found when both unequal masses and spins are considered. Because understanding the cause and magnitude of each component of this kick may be complicated in inspiral simulations, we consider these effects in the context of a simple test problem. We study recoils from collisions of binaries with initially head-on trajectories, starting with the simplest case of equal masses with no spin; adding spin and varying the mass ratio, both separately and jointly. We find spin-induced recoils to be significant even in head-on configurations. Additionally, it appears that the scaling of transverse kicks with spins is consistent with post-Newtonian (PN) theory, even though the kick is generated in the nonlinear merger interaction, where PN theory should not apply. This suggests that a simple heuristic description might be effective in the estimation of spin-kicks.

Choi, Dae-Il; Kelly, Bernard J.; Boggs, William D.; Baker, John G.; Centrella, Joan; Van Meter, James

2007-01-01

77

Anatomy of the Binary Black Hole Recoil: A Multipolar Analysis

NASA Technical Reports Server (NTRS)

We present a multipolar analysis of the recoil velocity computed in recent numerical simulations of binary black hole coalescence, for both unequal masses and non-zero, non-precessing spins. We show that multipole moments up to and including 1 = 4 are sufficient to accurately reproduce the final recoil velocity (= 98%) and that only a few dominant modes contribute significantly to it (2 95%). We describe how the relative amplitude, and more importantly, the relative phase, of these few modes control the way in which the recoil builds up throughout the inspiral, merger, and ring-down phases. We also find that the numerical results can be reproduced, to a high level of accuracy, by an effective Newtonian formula for the multipole moments obtained by replacing in the Newtonian formula the radial separation with an effective radius computed from the numerical data. Beyond the merger, the numerical results are reproduced by a superposition of three Kerr quasi-normal modes. Analytic formulae, obtained by expressing the multipole moments in terms of the fundamental QNMs of a Kerr BH, are able to explain the onset and amount of '.anti-kick" for each of the simulations. Lastly, we apply this multipolar analysis to understand the remarkable difference between the amplitudes of planar and non-planar kicks for equal-mass spinning black holes.

Schnittman, Jeremy; Buonanno, Alessandra; vanMeter, James R.; Baker, John G.; Boggs, William D.; Centrella, Joan; Kelly, Bernard J.; McWilliams, Sean T.

2007-01-01

78

Anatomy of the binary black hole recoil: A multipolar analysis

We present a multipolar analysis of the gravitational recoil computed in recent numerical simulations of binary black hole (BH) coalescence, for both unequal masses and non-zero, non-precessing spins. We show that multipole moments up to and including l=4 are sufficient to accurately reproduce the final recoil velocity (within ~2%) and that only a few dominant modes contribute significantly to it (within ~5%). We describe how the relative amplitudes, and more importantly, the relative phases, of these few modes control the way in which the recoil builds up throughout the inspiral, merger, and ringdown phases. We also find that the numerical results can be reproduced by an ``effective Newtonian'' formula for the multipole moments obtained by replacing the radial separation in the Newtonian formulae with an effective radius computed from the numerical data. Beyond the merger, the numerical results are reproduced by a superposition of three Kerr quasi-normal modes (QNMs). Analytic formulae, obtained by expressing the multipole moments in terms of the fundamental QNMs of a Kerr BH, are able to explain the onset and amount of ``anti-kick'' for each of the simulations. Lastly, we apply this multipolar analysis to help explain the remarkable difference between the amplitudes of planar and non-planar kicks for equal-mass spinning black holes.

Jeremy D. Schnittman; Alessandra Buonanno; James R. van Meter; John G. Baker; William D. Boggs; Joan Centrella; Bernard J. Kelly; Sean T. McWilliams

2007-12-20

79

Quantum fluid model of coherent stimulated radiation by a dense relativistic cold electron beam

Using a quantum fluid model, the linear dispersion relation for FEL pumped by a short wavelength laser wiggler is deduced. Subsequently, a new quantum corrected resonance condition is obtained. It is shown that, in the limit of low energy electron beam and low frequency pump, the quantum recoil effect can be neglected, recovering the classical FEL resonance condition, k{sub s}=4k{sub w}?{sup 2}. On the other hand, for short wavelength and high energy electron beam, the quantum recoil effect becomes strong and the resonance condition turns into k{sub s}=2?(k{sub w}/?{sub c})?{sup 3/2}, with ?{sub c} being the reduced Compton wavelength. As a result, a set of nonlinear coupled equations, which describes the quantum FEL dynamics as a three-wave interaction, is obtained. Neglecting wave propagation effects, this set of equations is solved numerically and results are presented.

Monteiro, L. F.; Serbeto, A.; Tsui, K. H. [Instituto de Física, Universidade Federal Fluminense, Campus da Praia Vermelha, Niterói, RJ 24210-346 (Brazil)] [Instituto de Física, Universidade Federal Fluminense, Campus da Praia Vermelha, Niterói, RJ 24210-346 (Brazil); Mendonça, J. T.; Galvão, R. M. O. [Instituto de Física, Universidade de São Paulo, São Paulo, SP 05508-090 (Brazil)] [Instituto de Física, Universidade de São Paulo, São Paulo, SP 05508-090 (Brazil)

2013-07-15

80

Stochasticity Effects in Quantum Radiation Reaction

NASA Astrophysics Data System (ADS)

When an ultrarelativistic electron beam collides with a sufficiently intense laser pulse, radiation-reaction effects can strongly alter the beam dynamics. In the realm of classical electrodynamics, radiation reaction has a beneficial effect on the electron beam as it tends to reduce its energy spread. Here we show that when quantum effects become important, radiation reaction induces the opposite effect; i.e., the energy distribution of the electron beam spreads out after interacting with the laser pulse. We identify the physical origin of this opposite tendency in the intrinsic stochasticity of photon emission, which becomes substantial in the quantum regime. Our numerical simulations indicate that the predicted effects of the stochasticity can be measured already with presently available lasers and electron accelerators.

Neitz, N.; Di Piazza, A.

2013-08-01

81

Significant quantum effects in hydrogen activation.

Dissociation of molecular hydrogen is an important step in a wide variety of chemical, biological, and physical processes. Due to the light mass of hydrogen, it is recognized that quantum effects are often important to its reactivity. However, understanding how quantum effects impact the reactivity of hydrogen is still in its infancy. Here, we examine this issue using a well-defined Pd/Cu(111) alloy that allows the activation of hydrogen and deuterium molecules to be examined at individual Pd atom surface sites over a wide range of temperatures. Experiments comparing the uptake of hydrogen and deuterium as a function of temperature reveal completely different behavior of the two species. The rate of hydrogen activation increases at lower sample temperature, whereas deuterium activation slows as the temperature is lowered. Density functional theory simulations in which quantum nuclear effects are accounted for reveal that tunneling through the dissociation barrier is prevalent for H2 up to ?190 K and for D2 up to ?140 K. Kinetic Monte Carlo simulations indicate that the effective barrier to H2 dissociation is so low that hydrogen uptake on the surface is limited merely by thermodynamics, whereas the D2 dissociation process is controlled by kinetics. These data illustrate the complexity and inherent quantum nature of this ubiquitous and seemingly simple chemical process. Examining these effects in other systems with a similar range of approaches may uncover temperature regimes where quantum effects can be harnessed, yielding greater control of bond-breaking processes at surfaces and uncovering useful chemistries such as selective bond activation or isotope separation. PMID:24684530

Kyriakou, Georgios; Davidson, Erlend R M; Peng, Guowen; Roling, Luke T; Singh, Suyash; Boucher, Matthew B; Marcinkowski, Matthew D; Mavrikakis, Manos; Michaelides, Angelos; Sykes, E Charles H

2014-05-27

82

Significant Quantum Effects in Hydrogen Activation

Dissociation of molecular hydrogen is an important step in a wide variety of chemical, biological, and physical processes. Due to the light mass of hydrogen, it is recognized that quantum effects are often important to its reactivity. However, understanding how quantum effects impact the reactivity of hydrogen is still in its infancy. Here, we examine this issue using a well-defined Pd/Cu(111) alloy that allows the activation of hydrogen and deuterium molecules to be examined at individual Pd atom surface sites over a wide range of temperatures. Experiments comparing the uptake of hydrogen and deuterium as a function of temperature reveal completely different behavior of the two species. The rate of hydrogen activation increases at lower sample temperature, whereas deuterium activation slows as the temperature is lowered. Density functional theory simulations in which quantum nuclear effects are accounted for reveal that tunneling through the dissociation barrier is prevalent for H2 up to ?190 K and for D2 up to ?140 K. Kinetic Monte Carlo simulations indicate that the effective barrier to H2 dissociation is so low that hydrogen uptake on the surface is limited merely by thermodynamics, whereas the D2 dissociation process is controlled by kinetics. These data illustrate the complexity and inherent quantum nature of this ubiquitous and seemingly simple chemical process. Examining these effects in other systems with a similar range of approaches may uncover temperature regimes where quantum effects can be harnessed, yielding greater control of bond-breaking processes at surfaces and uncovering useful chemistries such as selective bond activation or isotope separation. PMID:24684530

2014-01-01

83

Effective Evolution Equations from Quantum Dynamics

In these notes we review the material presented at the summer school on "Mathematical Physics, Analysis and Stochastics" held at the University of Heidelberg in July 2014. We consider the time-evolution of quantum systems and in particular the rigorous derivation of effective equations approximating the many-body Schr\\"odinger dynamics in certain physically interesting regimes.

Niels Benedikter; Marcello Porta; Benjamin Schlein

2015-02-09

84

Quantum gravity effects on compact star cores

NASA Astrophysics Data System (ADS)

Using the Tolman-Oppenheimer-Volkoff equation and the equation of state of zero temperature ultra-relativistic Fermi gas based on generalized uncertainty principle (GUP), the quantum gravitational effects on the cores of compact stars are discussed. Our results show that 2m(r)/r varies with r. Quantum gravity plays an important role in the region r˜103r0, where r0˜?0lp, lp is the Planck length and ?0 is a dimensionless parameter accounting for quantum gravity effects. Furthermore, near the center of compact stars, we find that the metric components are g˜r4 and g=[1. All these effects are different from those obtained from classical gravity. These results can be applied to neutron stars or denser ones like quark stars. The observed masses of neutron stars (?2M?) indicate that ?0 can not exceed 1037, not as good as the upper bound ?0<1034 from simple electroweak consideration. This means that incorporating either quantum gravity effects or nuclear interactions, one obtains almost the same mass limits of neutron stars.

Wang, Peng; Yang, Haitang; Zhang, Xiuming

2012-12-01

85

The Quantum Hall Effect in Graphene

We investigate the quantum Hall effect in graphene. We argue that in graphene in presence of an external magnetic field there is dynamical generation of mass by a rearrangement of the Dirac sea. We show that the mechanism breaks the lattice valley degeneracy only for the $n=0$ Landau levels and leads to the new observed $\

Paolo Cea

2011-01-29

86

Thermal disequilibrium effects in quantum reflection

We show that the quantum reflection coefficient of ultracold heavy atoms scattering off a dielectric surface can be tuned in a wide range by suitable choice of surface and environment temperatures. This effect results from a temperature-dependent repulsive part of the van der Waals-Casimir-Polder-Lifshitz atom-surface interaction potential.

Druzhinina, Viola; Mudrich, Marcel; Buchleitner, Andreas [Physikalisches Institut, Albert-Ludwigs Universitaet Freiburg, D-79104 Freiburg (Germany); Arnecke, Florian; Madronero, Javier [Physik Department, Technische Universitaet Muenchen, D-85747 Garching (Germany)

2010-09-15

87

Quantum Plasma Effects in the Classical Regime

For quantum effects to be significant in plasmas it is often assumed that the temperature over density ratio must be small. In this paper we challenge this assumption by considering the contribution to the dynamics from the electron spin properties. As a starting point we consider a multicomponent plasma model, where electrons with spin-up and spin-down are regarded as different

G. Brodin; M. Marklund; G. Manfredi

2008-01-01

88

Kondo Effect in Coupled Quantum Dots A. M. Chang+

, with emphasis on the semiconductor quantum dot system. The rich variety of behaviors, such as distinct quantum and shapes, e.g. in semiconductor quantum dots [2Â19], metallic quan- tum dots [20Â23], tunnel junctionsKondo Effect in Coupled Quantum Dots A. M. Chang+ , J. C. Chen+ Department of Physics, Duke

Chang, Albert

89

Room-Temperature Quantum Hall Effect in Graphene

The quantum Hall effect (QHE), one example of a quantum phenomenon that occurs on a truly macroscopic scale, has attracted intense interest since its discovery in 1980 and has helped elucidate many important aspects of quantum physics. It has also led to the establishment of a new metrological standard, the resistance quantum. Disappointingly, however, the QHE has been observed only

K. S. Novoselov; Philip Kim; Zhigang Jiang; Horst Stormer; Yuanbo Zhang; Sergey Morozov; G. S. Boebinger; P. Kim; A. K. Geim

2007-01-01

90

Unconventional Integer Quantum Hall Effect in Graphene

Monolayer graphite films, or graphene, have quasiparticle excitations that\\u000acan be described by 2+1 dimensional Dirac theory. We demonstrate that this\\u000aproduces an unconventional form of the quantized Hall conductivity $\\\\sigma_{xy}\\u000a= - (2 e^2\\/h)(2n+1)$ with $n=0,1,...$, that notably distinguishes graphene from\\u000aother materials where the integer quantum Hall effect was observed. This\\u000aunconventional quantization is caused by the quantum

V. P. Gusynin; S. G. Sharapov

2005-01-01

91

Unconventional Integer Quantum Hall effect in graphene

Monolayer graphite films, or graphene, have quasiparticle excitations that can be described by 2+1 dimensional Dirac theory. We demonstrate that this produces an unconventional form of the quantized Hall conductivity $\\sigma_{xy} = - (2 e^2/h)(2n+1)$ with $n=0,1,...$, that notably distinguishes graphene from other materials where the integer quantum Hall effect was observed. This unconventional quantization is caused by the quantum anomaly of the $n=0$ Landau level and was discovered in recent experiments on ultrathin graphite films.

V. P. Gusynin; S. G. Sharapov

2005-08-16

92

Oscillation and recoil of single and consecutively printed droplets.

In this study, the recoil and oscillation of single and consecutively printed drops on substrates of different wettabilities are examined using a high speed camera. The results show that, for a droplet impact on a dry surface at Weber number ~ O (1), both inertia and capillary effects are important in the initial spreading regime before the droplet starts to oscillate. For a substrate of higher wettability, drop oscillation decays faster due to a stronger viscous dissipation over a longer oscillation path parallel to the substrate. It is also found that when a drop impacts on a sessile drop sitting on a hydrophobic substrate, the combined drop recoil twice resulted from the coalescence of the two drops, whereas no recoil is observed for the impact of a single drop on a dry surface under the same condition. Furthermore, a single-degree-of-freedom vibration model for the height oscillation of single and combined drops on a hydrophobic substrate is established. For the condition considered, the model predictions match well with the experiments. The results also show the extent to which the increase in the liquid viscosity facilitates oscillation damping and the quantitative extension of the oscillation time of a combined drop compared to a single drop. PMID:23360081

Yang, Xin; Chhasatia, Viral H; Sun, Ying

2013-02-19

93

Effective equilibrium theory of nonequilibrium quantum transport

The theoretical description of strongly correlated quantum systems out of equilibrium presents several challenges and a number of open questions persist. Here, we focus on nonlinear electronic transport through an interacting quantum dot maintained at finite bias using a concept introduced by Hershfield [S. Hershfield, Phys. Rev. Lett. 70 2134 (1993)] whereby one can express such nonequilibrium quantum impurity models in terms of the system's Lippmann-Schwinger operators. These scattering operators allow one to reformulate the nonequilibrium problem as an effective equilibrium problem associated with a modified Hamiltonian. In this paper, we provide a pedagogical analysis of the core concepts of the effective equilibrium theory. First, we demonstrate the equivalence between observables computed using the Schwinger-Keldysh framework and the effective equilibrium approach, and relate Green's functions in the two theoretical frameworks. Second, we expound some applications of this method in the context of interacting quantum impurity models. We introduce a novel framework to treat effects of interactions perturbatively while capturing the entire dependence on the bias voltage. For the sake of concreteness, we employ the Anderson model as a prototype for this scheme. Working at the particle-hole symmetric point, we investigate the fate of the Abrikosov-Suhl resonance as a function of bias voltage and magnetic field. - Highlights: > Reformulation of steady-state nonequilibrium quantum transport, following Hershfield. > Derivation of effective equilibrium density operator using the 'open-system' approach. > Equivalence with the Keldysh description and formulas relating the two approaches. > Novel framework to treat interactions perturbatively. > Application to nonequilibrium Anderson model and fate of Abrikosov-Suhl resonance.

Dutt, Prasenjit [Department of Physics, Yale University, New Haven, CT 06520 (United States); Koch, Jens [Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208 (United States); Han, Jong [Department of Physics, State University of New York at Buffalo, Buffalo, NY 14260 (United States); Le Hur, Karyn, E-mail: karyn.lehur@yale.edu [Department of Physics, Yale University, New Haven, CT 06520 (United States)

2011-12-15

94

Quantum anomalous Hall effect with higher plateaus.

The quantum anomalous Hall (QAH) effect in magnetic topological insulators is driven by the combination of spontaneous magnetic moments and spin-orbit coupling. Its recent experimental discovery raises the question if higher plateaus can also be realized. Here, we present a general theory for a QAH effect with higher Chern numbers and show by first-principles calculations that a thin film magnetic topological insulator of Cr-doped Bi2(Se,Te)3 is a candidate for the C=2 QAH insulator. Remarkably, whereas a higher magnetic field leads to lower Hall conductance plateaus in the integer quantum Hall effect, a higher magnetic moment leads to higher Hall conductance plateaus in the QAH effect. PMID:24116800

Wang, Jing; Lian, Biao; Zhang, Haijun; Xu, Yong; Zhang, Shou-Cheng

2013-09-27

95

Quantum Hall effect in a vortex liquid

A two-dimensional superconducting film in a magnetic field is considered in the adiabatic limit when vortex dynamics is dominated by the Magnus force. By mapping a vortex liquid state into that of electrons in an effective magnetic field, I find that the Hall conductance is quantized as sigmaxy=(4e2\\/h)[1+n(2m-1)]\\/n with n,m>=1 integers, predicting a fractional quantum Hall effect in a boson

Baruch Horovitz

1995-01-01

96

Quantum Zeno effect in a multilevel molecule

We study the dynamics of the populations of a model molecule endowed with two sets of rotational levels of different parity, whose ground levels are energy degenerate and coupled by a constant interaction. The relaxation rate from one set of levels to the other one has an interesting dependence on the average collision frequency of the molecules in the gas. This is interpreted as a quantum Zeno effect due to the decoherence effects provoked by the molecular collisions.

D. Bruno; P. Facchi; S. Longo; P. Minelli; S. Pascazio; A. Scardicchio

2010-01-19

97

Zeeman Effect in Parabolic Quantum Dots

An unprecedentedly well resolved Zeeman effect has been observed when confined carriers moving along a closed mesoscopic path experience an external magnetic field orthogonal to the orbit plane. Large Zeeman splitting of excited higher angular momentum states is observed in the magnetoluminescence spectrum of quantum dots induced by self-organized InP islands on InGaAs\\/GaAs. The measured effect is quantitatively reproduced by

R. Rinaldi; P. V. Giugno; R. Cingolani; H. Lipsanen; M. Sopanen; J. Tulkki; J. Ahopelto

1996-01-01

98

The Quantum-Classical and Mind-Brain Linkages: The Quantum Zeno Effect in Binocular Rivalry

A quantum mechanical theory of the relationship between perceptions and brain dynamics based on von Neumann's theory of measurments is applied to a recent quantum theoretical treatment of binocular rivaly that makes essential use of the quantum Zeno effect to give good fits to the complex available empirical data. The often-made claim that decoherence effects in the warm, wet, noisy brain must eliminate quantum effects at the macroscopic scale pertaining to perceptions is examined, and it is argued, on the basis of fundamental principles. that the usual decoherence effects will not upset the quantum Zeno effect that is being exploited in the cited work.

Henry P. Stapp

2007-11-05

99

On the effective hydrodynamics of the fractional quantum Hall effect

NASA Astrophysics Data System (ADS)

We present here a classical hydrodynamic model of a two-dimensional fluid which has many properties of the fractional quantum Hall effect (FQHE). This model incorporates the FQHE relation between the vorticity and density of the fluid and exhibits the Hall viscosity and Hall conductivity found in FQHE liquids. We describe the relation of the model to the Chern-Simons-Ginzburg-Landau theory of FQHE and show how Laughlin's wavefunction is annihilated by the quantum velocity operator.

Abanov, Alexander G.

2013-07-01

100

Quantum oscillatory screening effects on the charge capture process in quantum plasmas

The quantum oscillatory screening effects on the charge capture process are investigated in quantum plasmas. The Bohr-Lindhard formalism with the modified Debye-Hückel potential is employed for obtaining the electron capture radius and probability as functions of the quantum wave number, projectile energy and ion charge number. It is shown that the oscillatory screening effects suppress the electron capture cross section

Sang-Chul Na; Young-Dae Jung

2008-01-01

101

Anomalous Nuclear Quantum Effects in Ice

The experimental volume of H$_2$O ice is smaller than that of D$_2$O, and this isotope shift, with anomalous sign, is not reproduced by state of art empirical potentials. We show that {\\it ab initio} density functional theory does reproduce it, accounting correctly for a subtle interplay between intermolecular libration modes, with a normal isotope effect, and intramolecular stretching modes. The latter have an anomalous inverse isotope shift on the volume, because of quantum effects related to the well known anticorrelation between the covalent and hydrogen bonds. We also show, both experimentally and theoretically that the volume's isotope shift of H$_2\\text{}^{18}$O ice has positive sign. Relative to the the classical limit, the net effect of quantum nuclei (H and O) on volume has the conventional (positive) sign at T=0 but it becomes negative above $\\sim 70$ K, indicating that it may be also relevant for liquid water.

Pamuk, B; Ramirez, R; Herrero, C P; Stephens, P W; Allen, P B; Fernandez-Serra, M V

2011-01-01

102

Effects of lasing in a one-dimensional quantum metamaterial

Electromagnetic pulse propagation in a quantum metamaterial - artificial, globally quantum coherent optical medium - is numerically simulated. We show that for the quantum metamaterials based on superconducting quantum bits, initialized in an easily reachable factorized state, lasing in microwave range is triggered, accompanied by the chaotization of qubit states and generation of higher harmonics. These effects may provide a tool for characterization and optimization of quantum metamaterial prototypes.

Hidehiro Asai; Sergey Savel'ev; Shiro Kawabata; Alexandre Zagoskin

2014-12-15

103

Quantum anomalous hall effect in Hg1-yMnyTe quantum wells.

The quantum Hall effect is usually observed when a two-dimensional electron gas is subjected to an external magnetic field, so that their quantum states form Landau levels. In this work we predict that a new phenomenon, the quantum anomalous Hall effect, can be realized in Hg{1-y}Mn{y}Te quantum wells, without an external magnetic field and the associated Landau levels. This effect arises purely from the spin polarization of the Mn atoms, and the quantized Hall conductance is predicted for a range of quantum well thickness and the concentration of the Mn atoms. This effect enables dissipationless charge current in spintronics devices. PMID:18851555

Liu, Chao-Xing; Qi, Xiao-Liang; Dai, Xi; Fang, Zhong; Zhang, Shou-Cheng

2008-10-01

104

Quantum Anomalous Hall Effect in Magnetically Doped InAs/GaSb Quantum Wells

NASA Astrophysics Data System (ADS)

The quantum anomalous Hall effect has recently been observed experimentally in thin films of Cr-doped (Bi,Sb)2Te3 at a low temperature (˜30 mK). In this work, we propose realizing the quantum anomalous Hall effect in more conventional diluted magnetic semiconductors with magnetically doped InAs/GaSb type-II quantum wells. Based on a four-band model, we find an enhancement of the Curie temperature of ferromagnetism due to band edge singularities in the inverted regime of InAs/GaSb quantum wells. Below the Curie temperature, the quantum anomalous Hall effect is confirmed by the direct calculation of Hall conductance. The parameter regime for the quantum anomalous Hall phase is identified based on the eight-band Kane model. The high sample quality and strong exchange coupling make magnetically doped InAs/GaSb quantum wells good candidates for realizing the quantum anomalous Hall insulator at a high temperature.

Wang, Qing-Ze; Liu, Xin; Zhang, Hai-Jun; Samarth, Nitin; Zhang, Shou-Cheng; Liu, Chao-Xing

2014-10-01

105

Quantum renormalization of the spin Hall effect.

By quantum Monte Carlo simulation of a realistic multiorbital Anderson impurity model, we study the spin-orbit interaction (SOI) of an Fe impurity in Au host metal. We show, for the first time, that the SOI is strongly renormalized by the quantum spin fluctuation. Based on this mechanism, we can explain why the gigantic spin Hall effect in Au with Fe impurities was observed in recent experiments, while it is not visible in the anomalous Hall effect. In addition, we show that the SOI is strongly renormalized by the Coulomb correlation U. Based on this picture, we can explain past discrepancies in the calculated orbital angular momenta for an Fe impurity in an Au host. PMID:20868117

Gu, Bo; Gan, Jing-Yu; Bulut, Nejat; Ziman, Timothy; Guo, Guang-Yu; Nagaosa, Naoto; Maekawa, Sadamichi

2010-08-20

106

Quantum Hall effect in a vortex liquid

NASA Astrophysics Data System (ADS)

A two-dimensional superconducting film in a magnetic field is considered in the adiabatic limit when vortex dynamics is dominated by the Magnus force. By mapping a vortex liquid state into that of electrons in an effective magnetic field, I find that the Hall conductance is quantized as ?xy=(4e2/h)[1+n(2m-1)]/n with n,m>=1 integers, predicting a fractional quantum Hall effect in a boson system. This phenomenon can also account for observed steps in the magnetization curve of YBa2Cu3O7-?. The feasibility of a vortex liquid, i.e., melting of a flux lattice at T=0 by quantum fluctuations, is studied.

Horovitz, Baruch

1995-02-01

107

Quantum gravity effects in the Kerr spacetime

We analyze the impact of the leading quantum gravity effects on the properties of black holes with nonzero angular momentum by performing a suitable renormalization group improvement of the classical Kerr metric within quantum Einstein gravity. In particular, we explore the structure of the horizons, the ergosphere, and the static limit surfaces as well as the phase space available for the Penrose process. The positivity properties of the effective vacuum energy-momentum tensor are also discussed and the 'dressing' of the black hole's mass and angular momentum are investigated by computing the corresponding Komar integrals. The pertinent Smarr formula turns out to retain its classical form. As for their thermodynamical properties, a modified first law of black-hole thermodynamics is found to be satisfied by the improved black holes (to second order in the angular momentum); the corresponding Bekenstein-Hawking temperature is not proportional to the surface gravity.

Reuter, M. [Institute of Physics, University of Mainz, Staudingerweg 7, D-55099 Mainz (Germany); Tuiran, E. [Departamento de Fisica, Universidad del Norte, Km 5 via a Puerto Colombia, AA-1569 Barranquilla (Colombia)

2011-02-15

108

Quantum Spin Hall Effect in Graphene

We study the effects of spin orbit interactions on the low energy electronic\\u000astructure of a single plane of graphene. We find that in an experimentally\\u000aaccessible low temperature regime the symmetry allowed spin orbit potential\\u000aconverts graphene from an ideal two dimensional semimetallic state to a quantum\\u000aspin Hall insulator. This novel electronic state of matter is gapped in

C. L. Kane; E. J. Mele

2005-01-01

109

The pinning effect in quantum dots

The pinning effect is studied in a Gaussian quantum dot using the improved Wigner-Brillouin perturbation theory (IWBPT) in the presence of electron-phonon interaction. The electron ground state plus one phonon state is degenerate with the electron in the first excited state. The electron-phonon interaction lifts the degeneracy and the first excited states get pinned to the ground state plus one phonon state as we increase the confinement frequency.

Monisha, P. J., E-mail: pjmonisha@gmail.com [School of Physics, University of Hyderabad, Hyderabad-500046 (India); Mukhopadhyay, Soma [Department of Physics, D V R College of Engineering and Technology, Hyderabad-502285 (India)

2014-04-24

110

Scattering and recoiling imaging code (SARIC)

NASA Astrophysics Data System (ADS)

A new classical ion trajectory simulation program based on the binary collision approximation has been developed in order to support the results of time-of-flight scattering and recoiling spectrometry (TOF-SARS) and scattering and recoiling imaging spectrometry (SARIS). The code was designed to provide information directly related to the TOF-SARS and SARIS measurements and to operate efficiently on small personal computers. The calculation uses the Ziegler-Biersack-Littmark (ZBL) universal screening function or the Moliére screening function to simulate the three-dimensional motion of atomic particles and includes simultaneous collisions involving several atoms. For TOF-SARS, the program calculates the energy and time-of-flight distributions of scattered and recoiled particles, polar (incident) angle ?-scans, and azimuthal angle ?-scans. For SARIS, the program provides images of the scattering and recoiling intensities in polar exit angle and azimuthal angle (?, ?)-space. A two-dimensional reliability factor ( R) has been developed in order to obtain a quantitative comparison of experimental and simulated images. Examples of simulations are presented for Ni{100}, {110} and {111} surfaces and a Pt{111} surface. The R-factor is used to quantitatively compare the simulated Pt{111} image to an experimentally emulated image.

Bykov, V.; Kim, C.; Sung, M. M.; Boyd, K. J.; Todorov, S. S.; Rabalais, J. W.

1996-07-01

111

Proton recoil scintillator neutron rem meter

A neutron rem meter utilizing proton recoil and thermal neutron scintillators to provide neutron detection and dose measurement. In using both fast scintillators and a thermal neutron scintillator the meter provides a wide range of sensitivity, uniform directional response, and uniform dose response. The scintillators output light to a photomultiplier tube that produces an electrical signal to an external neutron counter.

Olsher, Richard H. (Los Alamos, NM); Seagraves, David T. (Los Alamos, NM)

2003-01-01

112

Scintillation efficiency of nuclear recoil in liquid xenon

We present the results of a test done with a Liquid Xenon (LXe) detector for “Dark Matter” search, exposed to a neutron beam to produce nuclear recoil events simulating those which would be generated by WIMP's elastic scattering. The aim of the experiment was to measure directly the scintillation efficiency of nuclear recoil. The nuclear recoil considered in the test

F. Arneodo; B. Baiboussinov; A. Badertscher; P. Benetti; E. Bernardini; A. Bettini; A Borio di Tiogliole; R. Brunetti; A. Bueno; E. Calligarich; M. Campanelli; C. Carpanese; D. Cavalli; F. Cavanna; P. Cennini; S. Centro; A. Cesana; D. Cline; I De Mitri; R. Dolfini; A. Ferrari; A Gigli Berzolari; C. Matthey; F. Mauri; D. Mazza; L. Mazzone; G. Meng; C. Montanari; G. Nurzia; S. Otwinowski; O. Palamara; D. Pascoli; A. Pepato; S. Petrera; L. Periale; G Piano Mortari; A. Piazzoli; P. Picchi; F. Pietropaolo; T. Rancati; A. Rappoldi; G. L Raselli; D. Rebuzzi; J. P Revo; J. Rico; M. Rossella; C. Rossi; A. Rubbia; C. Rubbia; P. Sala; D. Scannicchio; F. Sergiampietri; S. Suzuki; M. Terrani; W. Tian; S. Ventura; C. Vignoli; H. Wang; J. Woo; Z. Xu

2000-01-01

113

Scintillation e$ciency of nuclear recoil in liquid xenon

We present the results of a test done with a Liquid Xenon (LXe) detector for 'Dark Mattera search, exposed to a neutron beam to produce nuclear recoil events simulating those which would be generated by WIMP's elastic scattering. The aim of the experiment was to measure directly the scintillation e$ciency of nuclear recoil. The nuclear recoil considered in the test

F. Arneodo; B. Baiboussinov; A. Badertscher; P. Benetti; E. Bernardini; A. Bettini; A. Borio; R. Brunetti; A. Bueno; E. Calligarich; M. Campanelli; C. Carpanese; D. Cavalli; F. Cavanna; P. Cennini; A. Cesana; D. Cline; I. De Mitri; R. Dol; A. Ferrari; A. Gigli Berzolari; C. Matthey; F. Mauri; D. Mazza; L. Mazzone; G. Meng; C. Montanari; G. Nurzia; S. Otwinowski; O. Palamara; D. Pascoli; A. Pepato; S. Petrera; L. Periale; G. Piano Mortari; A. Piazzoli; P. Picchi; F. Pietropaolo; T. Rancati; A. Rappoldi; G. L. Raselli; D. Rebuzzi; J. Rico; M. Rossella; C. Rossi; A. Rubbia; C. Rubbia; P. Sala; D. Scannicchio; F. Sergiampietri; S. Suzuki; M. Terrani; W. Tian; S. Ventura; C. Vignoli; H. Wang; J. Woo; Z. Xu

114

A programmable quantum current standard from the Josephson and the quantum Hall effects

We propose a way to realize a programmable quantum current standard (PQCS) from the Josephson voltage standard and the quantum Hall resistance standard (QHR) exploiting the multiple connection technique provided by the quantum Hall effect (QHE) and the exactness of the cryogenic current comparator. The PQCS could lead to breakthroughs in electrical metrology like the realization of a programmable quantum current source, a quantum ampere-meter, and a simplified closure of the quantum metrological triangle. Moreover, very accurate universality tests of the QHE could be performed by comparing PQCS based on different QHRs.

Poirier, W., E-mail: wilfrid.poirier@lne.fr; Lafont, F.; Djordjevic, S.; Schopfer, F.; Devoille, L. [Quantum metrology group, Laboratoire National de métrologie et d'Essais, 29 avenue Roger Hennequin, 78197 Trappes (France)

2014-01-28

115

Quantum confined Stark effect in Gaussian quantum wells: A tight-binding study

The main characteristics of the quantum confined Stark effect (QCSE) are studied theoretically in quantum wells of Gaussian profile. The semi-empirical tight-binding model and the Green function formalism are applied in the numerical calculations. A comparison of the QCSE in quantum wells with different kinds of confining potential is presented.

Ramírez-Morales, A.; Martínez-Orozco, J. C.; Rodríguez-Vargas, I. [Unidad Académica de Física, Universidad Autónoma de Zacatecas, Calzada Solidaridad Esquina Con Paseo La Bufa S/N, 98060 Zacatecas, Zac. (Mexico)

2014-05-15

116

We study transfer of a single-electron through a quantum ring capacitively coupled to the charged quantum dot placed in its center. For this purpose we solve the time-dependent Schrödinger equation for the pair of particles: the electron traveling through the ring and the other carrier confined within the quantum dot. The correlation effects due to the interaction between the charge

T. Chwiej; K. Kutorasinski

2010-01-01

117

Quantum theory of the inverse Faraday effect

NASA Astrophysics Data System (ADS)

We provide a quantum theoretical description of the magnetic polarization induced by intense circularly polarized light in a material. Such effect—commonly referred to as the inverse Faraday effect—is treated using beyond-linear response theory, considering the applied electromagnetic field as external perturbation. An analytical time-dependent solution of the Liouville-von Neumann equation to second order is obtained for the density matrix and used to derive expressions for the optomagnetic polarization. Two distinct cases are treated, the long-time adiabatic limit of polarization imparted by continuous wave irradiation, and the full temporal shape of the transient magnetic polarization induced by a short laser pulse. We further derive expressions for the Verdet constants for the inverse, optomagnetic Faraday effect and for the conventional, magneto-optical Faraday effect and show that they are in general different. Additionally, we derive expressions for the Faraday and inverse Faraday effects within the Drude-Lorentz theory and demonstrate that their equality does not hold in general, but only for dissipationless media. As an example, we perform initial quantum mechanical calculations of the two Verdet constants for a hydrogenlike atom and we extract the trends. We observe that one reason for a large inverse Faraday effect in heavy atoms is the spatial extension of the wave functions rather than the spin-orbit interaction, which nonetheless contributes positively.

Battiato, M.; Barbalinardo, G.; Oppeneer, P. M.

2014-01-01

118

Fractional Quantum Hall Effect from Phenomenological Bosonization

NASA Astrophysics Data System (ADS)

In this work we propose a model of the fractional quantum Hall effect within conventional one-dimensional bosonization. It is shown that in this formalism the resulting bosonized fermion operator corresponding to momenta of Landau gauge wave function is effectively two-dimensional. At special filling factors the bulk gets gapped, and the theory is described by a sine-Gordon model. The edges are shown to be gapless, chiral, and carrying a fractional charge. The hierarchy of obtained fractional charges is consistent with existing experiments and theories. It is also possible to draw a connection to composite fermion description and to the Laughlin many-body wave function.

Zyuzin, Vladimir

2013-03-01

119

Quantum and medium effects in (resonant) leptogenesis

NASA Astrophysics Data System (ADS)

Leptogenesis offers a very attractive explanation for the origin of the baryon asymmetry of the universe. Such scenarios based on leptonic CP-violation can be realized already within minimalistic seesaw extensions of the standard model. Apart from model building issues the answer to the question of whether a given particle theory can explain the observed baryon number density depends also on the detailed statistical evolution of the asymmetry. The CP-violation within a given model leads to an asymmetry only if it is accompanied by an out-of-equilibrium evolution in the early universe. Most existing analyses employ Boltzmann-like equations (BEs) to describe it. In this context fundamental issues arise which can be addressed in the framework of non-equilibrium quantum field theory (NEQFT). Here, the relevance of quantum and medium effects for thermal leptogenesis is investigated. Within the 2PI-formalism of NEQFT, questions such as that for the justification of the particle picture arise naturally in subsequent approximations when BEs are to be derived. This specific problem is particularly important in the case of resonant leptogenesis where the relevant particle states are almost degenerate in mass. It is found that Boltzmann like equations can (only) be obtained in certain cases. But it is then possible to account for corrections due to quantum and medium effects.

Hohenegger, Andreas

2014-03-01

120

BlackMax: A black-hole event generator with rotation, recoil, split branes, and brane tension

We present a comprehensive black-hole event generator, BlackMax, which simulates the experimental signatures of microscopic and Planckian black-hole production and evolution at the LHC in the context of brane world models with low-scale quantum gravity. The generator is based on phenomenologically realistic models free of serious problems that plague low-scale gravity, thus offering more realistic predictions for hadron-hadron colliders. The generator includes all of the black-hole gray-body factors known to date and incorporates the effects of black-hole rotation, splitting between the fermions, nonzero brane tension, and black-hole recoil due to Hawking radiation (although not all simultaneously). The generator can be interfaced with Herwig and Pythia. The main code can be downloaded from http://www-pnp.physics.ox.ac.uk/{approx}issever/BlackMax/blackmax.html.

Dai Dechang; Starkman, Glenn [Case Western Reserve University, Cleveland, Ohio 44106-7079 (United States); Stojkovic, Dejan [Department of Physics, SUNY at Buffalo, Buffalo, New York 14260-1500 (United States); Issever, Cigdem; Tseng, Jeff [University of Oxford, Oxford (United Kingdom); Rizvi, Eram [Queen Mary, University of London, London (United Kingdom)

2008-04-01

121

Oscillatory screening and quantum interference effects on electron collisions in quantum plasmas

The oscillatory screening and collision-induced quantum interference effects on electron–electron collisions are investigated in dense quantum plasmas. The modified Debye–Hückel potential with the total spin states of the system is considered to obtain the differential electron–electron scattering cross section in quantum plasmas. It is shown that the electron–electron scattering cross section decreases with an increase of the quantum wave number.

Sang-Chul Na; Young-Dae Jung

2008-01-01

122

Ionization and scintillation of nuclear recoils in gaseous xenon

Ionization and scintillation produced by nuclear recoils in gaseous xenon at approximately 14 bar have been simultaneously observed in an electroluminescent time projection chamber. Neutrons from radioisotope $\\alpha$-Be neutron sources were used to induce xenon nuclear recoils, and the observed recoil spectra were compared to a detailed Monte Carlo employing estimated ionization and scintillation yields for nuclear recoils. The ability to discriminate between electronic and nuclear recoils using the ratio of ionization to primary scintillation is demonstrated. These results encourage further investigation on the use of xenon in the gas phase as a detector medium in dark matter direct detection experiments.

J. Renner; V. M. Gehman; A. Goldschmidt; H. S. Matis; T. Miller; Y. Nakajima; D. Nygren; C. A. B. Oliveira; D. Shuman; V. Álvarez; F. I. G. Borges; S. Cárcel; J. Castel; S. Cebrián; A. Cervera; C. A. N. Conde; T. Dafni; T. H. V. T. Dias; J. Díaz; R. Esteve; P. Evtoukhovitch; L. M. P. Fernandes; P. Ferrario; A. L. Ferreira; E. D. C. Freitas; A. Gil; H. Gómez; J. J. Gómez-Cadenas; D. González-Díaz; R. M. Gutiérrez; J. Hauptman; J. A. Hernando Morata; D. C. Herrera; F. J. Iguaz; I. G. Irastorza; M. A. Jinete; L. Labarga; A. Laing; I. Liubarsky; J. A. M. Lopes; D. Lorca; M. Losada; G. Luzón; A. Marí; J. Martín-Albo; A. Martínez; A. Moiseenko; F. Monrabal; M. Monserrate; C. M. B. Monteiro; F. J. Mora; L. M. Moutinho; J. Muñoz Vidal; H. Natal da Luz; G. Navarro; M. Nebot-Guinot; R. Palma; J. Pérez; J. L. Pérez Aparicio; L. Ripoll; A. Rodríguez; J. Rodríguez; F. P. Santos; J. M. F. dos Santos; L. Seguí; L. Serra; A. Simón; C. Sofka; M. Sorel; J. F. Toledo; A. Tomás; J. Torrent; Z. Tsamalaidze; J. F. C. A. Veloso; J. A. Villar; R. C. Webb; J. White; N. Yahlali

2014-09-09

123

Ionization and scintillation of nuclear recoils in gaseous xenon

Ionization and scintillation produced by nuclear recoils in gaseous xenon at approximately 14 bar have been simultaneously observed in an electroluminescent time projection chamber. Neutrons from radioisotope $\\alpha$-Be neutron sources were used to induce xenon nuclear recoils, and the observed recoil spectra were compared to a detailed Monte Carlo employing estimated ionization and scintillation yields for nuclear recoils. The ability to discriminate between electronic and nuclear recoils using the ratio of ionization to primary scintillation is demonstrated. These results encourage further investigation on the use of xenon in the gas phase as a detector medium in dark matter direct detection experiments.

Renner, J; Goldschmidt, A; Matis, H S; Miller, T; Nakajima, Y; Nygren, D; Oliveira, C A B; Shuman, D; Álvarez, V; Borges, F I G; Cárcel, S; Castel, J; Cebrián, S; Cervera, A; Conde, C A N; Dafni, T; Dias, T H V T; Díaz, J; Esteve, R; Evtoukhovitch, P; Fernandes, L M P; Ferrario, P; Ferreira, A L; Freitas, E D C; Gil, A; Gómez, H; Gómez-Cadenas, J J; González-Díaz, D; Gutiérrez, R M; Hauptman, J; Morata, J A Hernando; Herrera, D C; Iguaz, F J; Irastorza, I G; Jinete, M A; Labarga, L; Laing, A; Liubarsky, I; Lopes, J A M; Lorca, D; Losada, M; Luzón, G; Marí, A; Martín-Albo, J; Martínez, A; Moiseenko, A; Monrabal, F; Monserrate, M; Monteiro, C M B; Mora, F J; Moutinho, L M; Vidal, J Muñoz; da Luz, H Natal; Navarro, G; Nebot-Guinot, M; Palma, R; Pérez, J; Aparicio, J L Pérez; Ripoll, L; Rodríguez, A; Rodríguez, J; Santos, F P; Santos, J M F dos; Seguí, L; Serra, L; Simón, A; Sofka, C; Sorel, M; Toledo, J F; Tomás, A; Torrent, J; Tsamalaidze, Z; Veloso, J F C A; Villar, J A; Webb, R C; White, J; Yahlali, N

2014-01-01

124

Angular dependence of recoil proton polarization in high-energy \\gamma d \\to p n

We measured the angular dependence of the three recoil proton polarization components in two-body photodisintegration of the deuteron at a photon energy of 2 GeV. These new data provide a benchmark for calculations based on quantum chromodynamics. Two of the five existing models have made predictions of polarization observables. Both explain the longitudinal polarization transfer satisfactorily.. Transverse polarizations are not well described, but suggest isovector dominance.

Jiang, X; Benmokhtar, F; Camsonne, A; Chen, J P; Choi, S; Chudakov, E; Cusanno, F; De Jager, C W; De Leo, R; Deur, A; Dutta, D; Garibaldi, F; Gaskell, D; Gayou, O; Gilman, R; Glashauser, C; Hamilton, D; Hansen, O; Higinbotham, D W; Holt, R J; Jones, M K; Kaufman, L J; Kinney, E R; Krämer, K; Lagamba, L; Lerose, J; Lhuillier, D; Lindgren, R; Liyanage, N; McCormick, K; Meziani, Z E; Michaels, R; Moffit, B; Monaghan, P; Nanda, S; Paschke, K D; Perdrisat, C F; Punjabi, V; Qattan, I A; Ransome, R D; Reimer, P E; Reitz, B; Saha, A; Schulte, E C; Sheyor, R; Slifer, K J; Solvignon, P; Sulkosky, V; Urciuoli, G M; Voutier, E; Wang, K; Wijesooriya, K; Wojtsekhowski, B; Zhu, L

2007-01-01

125

We measured the angular dependence of the three recoil-proton polarization components in two-body photodisintegration of the deuteron at a photon energy of 2 GeV. These new data provide a benchmark for calculations based on quantum chromodynamics. Two of the five existing models have made predictions of polarization observables. Both explain the longitudinal polarization transfer satisfactorily. Transverse polarizations are not well described, but suggest isovector dominance.

X. Jiang; J. Arrington; F. Benmokhtar; A. Camsonne; J. P. Chen; S. Choi; E. Chudakov; F. Cusanno; A. Deur; D. Dutta; F. Garibaldi; D. Gaskell; O. Gayou; R. Gilman; C. Glashauser; D. Hamilton; O. Hansen; D. W. Higinbotham; R. J. Holt; C. W. de Jager; M. K. Jones; L. J. Kaufman; E. R. Kinney; K. Kramer; L. Lagamba; R. de Leo; J. Lerose; D. Lhuillier; R. Lindgren; N. Liyanage; K. McCormick; Z.-E. Meziani; R. Michaels; B. Mof?t; P. Monaghan; S. Nanda; K. D. Paschke; C. F. Perdrisat; V. Punjabi; I. A. Qattan; R. D. Ransome; P. E. Reimer; B. Reitz; A. Saha; E. C. Schulte; R. Sheyor; K. Slifer; P. Solvignon; V. Sulkosky; G. M. Urciuoli; E. Voutier; K. Wang; K. Wijesooriya; B. Wojtsekhowski; and L. Zhu

2007-05-01

126

Angular dependence of recoil proton polarization in high-energy ?d \\to p n

We measured the angular dependence of the three recoil proton polarization components in two-body photodisintegration of the deuteron at a photon energy of 2 GeV. These new data provide a benchmark for calculations based on quantum chromodynamics. Two of the five existing models have made predictions of polarization observables. Both explain the longitudinal polarization transfer satisfactorily.. Transverse polarizations are not well described, but suggest isovector dominance.

X. Jiang; J. Arrington; F. Benmokhtar; A. Camsonne; J. P. Chen; S. Choi; E. Chudakov; F. Cusanno; A. Deur; D. Dutta; F. Garibaldi; D. Gaskell; O. Gayou; R. Gilman; C. Glashauser; D. Hamilton; O. Hansen; D. W. Higinbotham; R. J. Holt; C. W. de Jager; M. K. Jones; L. J. Kaufman; E. R. Kinney; K. Kramer; L. Lagamba; R. de Leo; J. Lerose; D. Lhuillier; R. Lindgren; N. Liyanage; K. McCormick; Z. -E. Meziani; R. Michaels; B. Moffit; P. Monaghan; S. Nanda; K. D. Paschke; C. F. Perdrisat; V. Punjabi; I. A. Qattan; R. D. Ransome; P. E. Reimer; B. Reitz; A. Saha; E. C. Schulte; R. Sheyor; K. Slifer; P. Solvignon; V. Sulkosky; G. M. Urciuoli; E. Voutier; K. Wang; K. Wijesooriya; B. Wojtsekhowski; L. Zhu

2007-02-02

127

Angular dependence of recoil proton polarization in high-energy \\gamma d \\to p n

We measured the angular dependence of the three recoil proton polarization components in two-body photodisintegration of the deuteron at a photon energy of 2 GeV. These new data provide a benchmark for calculations based on quantum chromodynamics. Two of the five existing models have made predictions of polarization observables. Both explain the longitudinal polarization transfer satisfactorily.. Transverse polarizations are not well described, but suggest isovector dominance.

X. Jiang; J. Arrington; F. Benmokhtar; A. Camsonne; J.P. Chen; S. Choi; E. Chudakov; F. Cusanno; A. Deur; D. Dutta; F. Garibaldi; D. Gaskell; O. Gayou; R. Gilman; C. Glashauser; D. Hamilton; O. Hansen; D.W. Higinbotham; R.J. Holt; C.W. de Jager; M.K. Jones; L.J. Kaufman; E.R. Kinney; K. Kramer; L. Lagamba; R. de Leo; J. Lerose; D. Lhuillier; R. Lindgren; N. Liyanage; K. McCormick; Z.-E. Meziani; R. Michaels; B. Moffit; P. Monaghan; S. Nanda; K.D. Paschke; C.F. Perdrisat; V. Punjabi; I.A. Qattan; R.D. Ransome; P.E. Reimer; B. Reitz; A. Saha; E.C. Schulte; R. Sheyor; K. Slifer; P. Solvignon; V. Sulkosky; G.M. Urciuoli; E. Voutier; K. Wang; K. Wijesooriya; B. Wojtsekhowski; L. Zhu

2007-02-26

128

We measured the angular dependence of the three recoil-proton polarization components in two-body photodisintegration of the deuteron at a photon energy of 2 GeV. These new data provide a benchmark for calculations based on quantum chromodynamics. Two of the five existing models have made predictions of polarization observables. Both explain the longitudinal polarization transfer satisfactorily. Transverse polarizations are not well described, but suggest isovector dominance. PMID:17501566

Jiang, X; Arrington, J; Benmokhtar, F; Camsonne, A; Chen, J P; Choi, S; Chudakov, E; Cusanno, F; Deur, A; Dutta, D; Garibaldi, F; Gaskell, D; Gayou, O; Gilman, R; Glashauser, C; Hamilton, D; Hansen, O; Higinbotham, D W; Holt, R J; de Jager, C W; Jones, M K; Kaufman, L J; Kinney, E R; Kramer, K; Lagamba, L; de Leo, R; Lerose, J; Lhuillier, D; Lindgren, R; Liyanage, N; McCormick, K; Meziani, Z-E; Michaels, R; Moffit, B; Monaghan, P; Nanda, S; Paschke, K D; Perdrisat, C F; Punjabi, V; Qattan, I A; Ransome, R D; Reimer, P E; Reitz, B; Saha, A; Schulte, E C; Sheyor, R; Slifer, K; Solvignon, P; Sulkosky, V; Urciuoli, G M; Voutier, E; Wang, K; Wijesooriya, K; Wojtsekhowski, B; Zhu, L

2007-05-01

129

Propagation effects in semiconductor multiple quantum well structures

NASA Astrophysics Data System (ADS)

The dynamics of radiatively coupled quantum well excitons is investigated. It is shown that collective effects determine the optical response of semiconductor multiple quantum well stacks. In multiple quantum well Bragg structures, collective phenomena manifest themselves as a superradiant decay of coherent electronic excitations. In anti-Bragg structures, the optical coupling induces an interwell energy transport and a splitting of the excitonic resonance.

Stroucken, Tineke; Knorr, Andreas; Koch, Stephan W.; Huebner, Martin; Kuhl, Juergen

1996-05-01

130

Memory Effects in Quantum Channel Discrimination Giulio Chiribella,1

Memory Effects in Quantum Channel Discrimination Giulio Chiribella,1 Giacomo M. D'Ariano,1 quantum-memory assisted protocols for discriminating quantum channels. We show that for optimal discrimination of memory channels, memory assisted protocols are needed. This leads to a new notion of distance

D'Ariano, Giacomo Mauro

131

TEMPERATURE EFFECTS AND TRANSPORT PHENOMENA IN TERAHERTZ QUANTUM CASCADE LASERS

TEMPERATURE EFFECTS AND TRANSPORT PHENOMENA IN TERAHERTZ QUANTUM CASCADE LASERS BY PHILIP C Quantum cascade lasers (QCL's) employ the mid- and far-infrared intersubband ra- diative transitions been possible without his ability to explain the often frustrating physics of quantum cascade lasers. I

Massachusetts at Lowell, University of

132

Quantum dissipative effects in graphenelike mirrors

NASA Astrophysics Data System (ADS)

We study quantum dissipative effects due to the accelerated motion of a single, imperfect, zero-width mirror. It is assumed that the microscopic degrees of freedom on the mirror are confined to it, like in plasma or graphene sheets. Therefore, the mirror is described by a vacuum polarization tensor ??? concentrated on a time-dependent surface. Under certain assumptions about the microscopic model for the mirror, we obtain a rather general expression for the Euclidean effective action, a functional of the time-dependent mirror’s position, in terms of two invariants that characterize the tensor ???. The final result can be written in terms of the TE and TM reflection coefficients of the mirror, with qualitatively different contributions coming from them. We apply that general expression to derive the imaginary part of the “in-out” effective action, which measures dissipative effects induced by the mirror’s motion, in different models, in particular for an accelerated graphene sheet.

Fosco, César D.; Lombardo, Fernando C.; Mazzitelli, Francisco D.; Remaggi, María L.

2013-11-01

133

Scintillation efficiency for low energy nuclear recoils in liquid xenon dark matter detectors

NASA Astrophysics Data System (ADS)

We perform a theoretical study of the scintillation efficiency of the low energy region crucial for liquid xenon dark matter detectors. We develop a computer program to simulate the cascading process of the recoiling xenon nucleus in liquid xenon and calculate the nuclear quenching effect due to atomic collisions. We use the electronic stopping power extrapolated from experimental data to the low energy region, and take into account the effects of electron escape from electron-ion pair recombination using the generalized Thomas-Imel model fitted to scintillation data. Our result agrees well with the experiments from neutron scattering and vanishes rapidly as the recoil energy drops below 3 keV.

Mu, Wei; Xiong, Xiaonu; Ji, Xiangdong

2015-02-01

134

In-plane magnetization-induced quantum anomalous Hall effect.

The quantum Hall effect can only be induced by an out-of-plane magnetic field for two-dimensional electron gases, and similarly, the quantum anomalous Hall effect has also usually been considered for systems with only out-of-plane magnetization. In the present work, we predict that the quantum anomalous Hall effect can be induced by in-plane magnetization that is not accompanied by any out-of-plane magnetic field. Two realistic two-dimensional systems, Bi2Te3 thin film with magnetic doping and HgMnTe quantum wells with shear strains, are presented and the general condition for the in-plane magnetization-induced quantum anomalous Hall effect is discussed based on the symmetry analysis. Nonetheless, an experimental setup is proposed to confirm this effect, the observation of which will pave the way to search for the quantum anomalous Hall effect in a wider range of materials. PMID:24010461

Liu, Xin; Hsu, Hsiu-Chuan; Liu, Chao-Xing

2013-08-23

135

In-Plane Magnetization-Induced Quantum Anomalous Hall Effect

NASA Astrophysics Data System (ADS)

The quantum Hall effect can only be induced by an out-of-plane magnetic field for two-dimensional electron gases, and similarly, the quantum anomalous Hall effect has also usually been considered for systems with only out-of-plane magnetization. In the present work, we predict that the quantum anomalous Hall effect can be induced by in-plane magnetization that is not accompanied by any out-of-plane magnetic field. Two realistic two-dimensional systems, Bi2Te3 thin film with magnetic doping and HgMnTe quantum wells with shear strains, are presented and the general condition for the in-plane magnetization-induced quantum anomalous Hall effect is discussed based on the symmetry analysis. Nonetheless, an experimental setup is proposed to confirm this effect, the observation of which will pave the way to search for the quantum anomalous Hall effect in a wider range of materials.

Liu, Xin; Hsu, Hsiu-Chuan; Liu, Chao-Xing

2013-08-01

136

Nuclear astrophysics studies by recoil mass separators.

NASA Astrophysics Data System (ADS)

It has been recently demonstrated that an accelerator mass spectrometry (AMS) system, used as a recoil separator in conjunction with a windowless gas target, can yield the high suppression factor needed to dispersively analyze radiative capture residues, with the aim of measuring cross sections in the sub-microbarn range. An experiment is underway utilizing a radioactive 7Be beam for the measurement of the cross section of the astrophysically important reaction 7Be(p, ?)8B at a center of mass energy ECM = 1 MeV. Preliminary results of this experiment are presented. The extension of the method to another reaction playing a key role in stellar evolution, i.e. 12C(?, ?)16O, requires an improvement of the angle- and momentum-acceptance of the recoil separator, the use of a jet gas target and of a specially designed low-threshold detector. The solutions proposed by a joint Italian-German project are discussed.

Gialanella, L.; Brand, K.; Campajola, L.; D'Onofrio, A.; Greife, U.; Morone, M. C.; Oliviero, G.; Ordine, A.; Roca, V.; Rolfs, C.; Romano, M.; Romoli, M.; Schmidt, S.; Schulte, W. H.; Strieder, F.; Terrasi, F.; Trautvetter, H. P.; Zahnow, D.

1997-11-01

137

Mathematics of the Quantum Zeno Effect

We present an overview of the mathematics underlying the quantum Zeno effect. Classical, functional analytic results are put into perspective and compared with more recent ones. This yields some new insights into mathematical preconditions entailing the Zeno paradox, in particular a simplified proof of Misra's and Sudarshan's theorem. We empahsise the complex-analytic structures associated to the issue of existence of the Zeno dynamics. On grounds of the assembled material, we reason about possible future mathematical developments pertaining to the Zeno paradox and its counterpart, the anti-Zeno paradox, both of which seem to be close to complete characterisations.

Andreas U. Schmidt

2003-07-21

138

Monte Carlo simulation of quantum Zeno effect in the brain

Environmental decoherence appears to be the biggest obstacle for successful construction of quantum mind theories. Nevertheless, the quantum physicist Henry Stapp promoted the view that the mind could utilize quantum Zeno effect to influence brain dynamics and that the efficacy of such mental efforts would not be undermined by environmental decoherence of the brain. To address the physical plausibility of Stapp's claim, we modeled the brain using quantum tunneling of an electron in a multiple-well structure such as the voltage sensor in neuronal ion channels and performed Monte Carlo simulations of quantum Zeno effect exerted by the mind upon the brain in the presence or absence of environmental decoherence. The simulations unambiguously showed that the quantum Zeno effect breaks down for timescales greater than the brain decoherence time. To generalize the Monte Carlo simulation results for any n-level quantum system, we further analyzed the change of brain entropy due to the mind probing actions and proved ...

Georgiev, Danko

2014-01-01

139

Low Momentum Classical Mechanics with Effective Quantum Potentials

A recently introduced effective quantum potential theory is studied in a low momentum region of phase space. This low momentum approximation is used to show that the new effective quantum potential induces a space-dependent mass and a smoothed potential both of them constructed from the classical potential. The exact solution of the approximated theory in one spatial dimension is found. The concept of effective transmission and reflection coefficients for effective quantum potentials is proposed and discussed in comparison with an analogous quantum statistical mixture problem. The results are applied to the case of a square barrier.

Fernando Haas

2005-03-02

140

Quantum Rotational Effects in Nanomagnetic Systems

NASA Astrophysics Data System (ADS)

Quantum tunneling of the magnetic moment in a nanomagnet must conserve the total angular momentum. For a nanomagnet embedded in a rigid body, reversal of the magnetic moment will cause the body to rotate as a whole. When embedded in an elastic environment, tunneling of the magnetic moment will cause local elastic twists of the crystal structure. In this thesis, I will present a theoretical study of the interplay between magnetization and rotations in a variety of nanomagnetic systems which have some degree of rotational freedom. We investigate the effect of rotational freedom on the tunnel splitting of a nanomagnet which is free to rotate about its easy axis. Calculating the exact instanton of the coupled equations of motion shows that mechanical freedom of the particle renormalizes the easy axis anisotropy, increasing the tunnel splitting. To understand magnetization dynamics in free particles, we study a quantum mechanical model of a tunneling spin embedded in a rigid rotor. The exact energy levels for a symmetric rotor exhibit first and second order quantum phase transitions between states with different values the magnetic moment. A quantum phase diagram is obtained in which the magnetic moment depends strongly on the moments of inertia. An intrinsic contribution to decoherence of current oscillations of a flux qubit must come from the angular momentum it transfers to the surrounding body. Within exactly solvable models of a qubit embedded in a rigid body and an elastic medium, we show that slow decoherence is permitted if the solid is macroscopically large. The spin-boson model is one of the simplest representations of a two-level system interacting with a quantum harmonic oscillator, yet has eluded a closed-form solution. I investigate some possible approaches to understanding its spectrum. The Landau-Zener dynamics of a tunneling spin coupled to a torsional resonator show that for certain parameter ranges the system exhibits multiple Landau-Zener transitions. These transitions coincide in time with changes in the oscillator dynamics. A large number of spins on a single oscillator coupled only through the in-phase oscillations behaves as a single large spin, greatly enhancing the spin-phonon coupling.

O'Keeffe, Michael F.

141

NASA Astrophysics Data System (ADS)

This paper investigates GaAs/AlGaAs modified quantum dot nanocrystal and GaAs/AlGaAs/GaAs/AlGaAs quantum dot-quantum well heteronanocrystal. These quantum dots have been analyzed by the finite element numerical methods. Simulations carried out for state n=1, l=0, and m=0 which are original, orbital, and magnetic state of quantum numbers. The effects of variation in radius layers such as total radius, GaAs core, shell and AlGaAs barriers radius on the wavelength and emission coefficient are studied. For the best time, it has also investigated the effect of mole fraction on emission coefficient. Meanwhile, one of the problems in biological applications is alteration of the emission wavelength of a quantum dot by changing in its dimension. This problem will be resolved by changing in potential profile.

Elyasi, P.; SalmanOgli, A.

2014-05-01

142

Fractional quantum Hall effect in optical lattices

We analyze a recently proposed method to create fractional quantum Hall (FQH) states of atoms confined in optical lattices [A. Soerensen et al., Phys. Rev. Lett. 94, 086803 (2005)]. Extending the previous work, we investigate conditions under which the FQH effect can be achieved for bosons on a lattice with an effective magnetic field and finite on-site interaction. Furthermore, we characterize the ground state in such systems by calculating Chern numbers which can provide direct signatures of topological order and explore regimes where the characterization in terms of wave-function overlap fails. We also discuss various issues which are relevant for the practical realization of such FQH states with ultracold atoms in an optical lattice, including the presence of a long-range dipole interaction which can improve the energy gap and stabilize the ground state. We also investigate a detection technique based on Bragg spectroscopy to probe these systems in an experimental realization.

Hafezi, M.; Demler, E.; Lukin, M. D. [Physics Department, Harvard University, Cambridge, Massachusetts 02138 (United States); Soerensen, A. S. [QUANTOP, Danish National Research Foundation Centre of Quantum Optics, Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen O (Denmark)

2007-08-15

143

Covariant effective action for loop quantum cosmology a la Palatini

In loop quantum cosmology, non-perturbative quantum gravity effects lead to the resolution of the big bang singularity by a quantum bounce without introducing any new degrees of freedom. Though fundamentally discrete, the theory admits a continuum description in terms of an effective Hamiltonian. Here we provide an algorithm to obtain the corresponding effective action, establishing in this way the covariance of the theory for the first time. This result provides new insights on the continuum properties of the discrete structure of quantum geometry and opens new avenues to extract physical predictions such as those related to gauge invariant cosmological perturbations.

Olmo, Gonzalo J. [Instituto de Estructura de la Materia, CSIC, Serrano 121, 28006 Madrid (Spain)] [Instituto de Estructura de la Materia, CSIC, Serrano 121, 28006 Madrid (Spain); Singh, Parampreet, E-mail: olmo@iem.cfmac.csic.es, E-mail: psingh@perimeterinstitute.ca [Perimeter Institute for Theoretical Physics, 31 Caroline Street North, Waterloo, Ontario N2L 2Y5 (Canada)] [Perimeter Institute for Theoretical Physics, 31 Caroline Street North, Waterloo, Ontario N2L 2Y5 (Canada)

2009-01-15

144

Approximate inclusion of quantum effects in transition path sampling

We propose a method for incorporating nuclear quantum effects in transition path sampling studies of systems that consist of a few degrees of freedom that must be treated quantum mechanically, while the rest are classical-like. We used the normal mode centroid method to describe the quantum subsystem, which is a method that is not CPU intensive but still reasonably accurate. We applied this mixed centroid?classical transition path sampling method to a model system that has nontrivial quantum behavior, and showed that it can capture the correct quantum dynamical features. PMID:20001028

Antoniou, Dimitri; Schwartz, Steven D.

2009-01-01

145

Engineering of perturbation effects in onion-like heteronanocrystal quantum dot-quantum well

NASA Astrophysics Data System (ADS)

In this article, the perturbation influences on optical characterization of quantum dot and quantum dot-quantum well (modified quantum dot) heteronanocrystal is investigated. The original aim of this article is to investigate the quantum dot-quantum well heteronanocrystal advantages and disadvantages, when used as a functionalized particle in biomedical applications. Therefore, all of the critical features of quantum dots are fundamentally studied and their influences on optical properties are simulated. For the first time, the perturbation effects on optical characteristics are observed in the quantum dot-quantum well heteronanocrystals by 8-band K.P theory. The impact of perturbation on optical features such as photoluminescence and shifting of wavelength is studied. The photoluminescence and operation wavelength of quantum dots play a vital role in biomedical applications, where their absorption and emission in biological assays are altered by shifting of wavelength. Furthermore, in biomedical applications, by tuning the emission wavelengths of the quantum dot into far-red and near-infrared ranges, non-invasive in-vivo imaging techniques have been easily developed. In this wavelength window, tissue absorption, scattering and auto-fluorescence intensities have minimum quantities; thus fixing or minimizing of wavelength shifting can be regarded as an important goal which is investigated in this work.

SalmanOgli, A.; Rostami, R.

2013-10-01

146

Noise Effects in Quantum Magic Squares Game

In the article we analyse how noisiness of quantum channels can influence the magic squares quantum pseudo-telepathy game. We show that the probability of success can be used to determine characteristics of quantum channels. Therefore the game deserves more careful study aiming at its implementation.

P. Gawron; J. A. Miszczak; J. Sladkowski

2008-01-31

147

On Quantum Effects in a Theory of Biological Evolution

a mathematical proof of evolution? As well as why is it that living organisms evolve. It is apparentOn Quantum Effects in a Theory of Biological Evolution M. A. Martin-Delgado Departamento de Fi that considers quantum effects on biological evolution starting from Chaitin's classical framework

Calude, Cristian S.

148

Microtubules: from classical properties to quantum effects in human cognition

Microtubules: from classical properties to quantum effects in human cognition Ivan Kukuljan properties, higher order assemblies and goes on to discuss the role of microtubules in human cognition. Here to be the medium for the quantum effects in human cognition. The microtubules turned out to be an amazing structure

Â?umer, Slobodan

149

Quantum effects on Rayleigh-Taylor instability in magnetized plasma

The effects of the quantum mechanism and magnetic field on Rayleigh-Taylor (RT) instability in an ideal incompressible plasma are investigated. The explicit expression of the linear growth rate is obtained in the presence of fixed boundary conditions. It is shown that the magnetic field has a stabilizing effect on RT instability similar to the behavior in classical plasmas and RT instability is affected significantly by quantum effects. Quantum effects are also shown to suppress RT instability with the appropriate physical quantities. Some astrophysical parameters are discussed as an example to investigate the new effects.

Cao Jintao; Ren Haijun [CAS Key Laboratory of Basic Plasma Physics, University of Science and Technology of China, Hefei 230026 (China); Wu Zhengwei [CAS Key Laboratory of Basic Plasma Physics, University of Science and Technology of China, Hefei 230026 (China); Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China); Chu, Paul K. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China)

2008-01-15

150

Effective equations for isotropic quantum cosmology including matter

Effective equations often provide powerful tools to develop a systematic understanding of detailed properties of a quantum system. This is especially helpful in quantum cosmology where several conceptual and technical difficulties associated with the full quantum equations can be avoided in this way. Here, effective equations for Wheeler-DeWitt and loop quantizations of spatially flat, isotropic cosmological models sourced by a massive or interacting scalar are derived and studied. The resulting systems are remarkably different from that given for a free, massless scalar. This has implications for the coherence of evolving states and the realization of a bounce in loop quantum cosmology.

Bojowald, Martin; Hernandez, Hector; Skirzewski, Aureliano [Institute for Gravitation and the Cosmos, Pennsylvania State University, 104 Davey Lab, University Park, Pennsylvania 16802 (United States); Universidad Autonoma de Chihuahua, Facultad de Ingenieria, Nuevo Campus Universitario, Chihuahua 31125 (Mexico); Centro de Fisica Fundamental, Universidad de los Andes, Merida 5101 (Venezuela)

2007-09-15

151

Quantum Hall effect in hydrogenated graphene.

The quantum Hall effect is observed in a two-dimensional electron gas formed in millimeter-scale hydrogenated graphene, with a mobility less than 10??cm2/V·s and corresponding Ioffe-Regel disorder parameter (k(F)?)(-1) ? 1. In a zero magnetic field and low temperatures, the hydrogenated graphene is insulating with a two-point resistance of the order of 250h/e2. The application of a strong magnetic field generates a negative colossal magnetoresistance, with the two-point resistance saturating within 0.5% of h/2e2 at 45 T. Our observations are consistent with the opening of an impurity-induced gap in the density of states of graphene. The interplay between electron localization by defect scattering and magnetic confinement in two-dimensional atomic crystals is discussed. PMID:23679754

Guillemette, J; Sabri, S S; Wu, Binxin; Bennaceur, K; Gaskell, P E; Savard, M; Lévesque, P L; Mahvash, F; Guermoune, A; Siaj, M; Martel, R; Szkopek, T; Gervais, G

2013-04-26

152

Quantum Numbers of Textured Hall Effect Quasiparticles

We propose a class of variational wave functions with slow variation in spin and charge density and simple vortex structure at infinity, which properly generalize both the Laughlin quasiparticles and baby Skyrmions. We argue, on the basis of these wave functions and a spin-statistics relation in the relevant effective field theory, that the spin of the corresponding quasiparticle has a fractional part related in a universal fashion to the properties of the bulk state. We propose a direct experimental test of this claim. We show that certain spin-singlet quantum Hall states can be understood as arising from primary polarized states by Skyrmion condensation. {copyright} {ital 1996 The American Physical Society.}

Nayak, C. [Department of Physics, Joseph Henry Laboratories, Princeton University, Princeton, New Jersey 08544 (United States)] [Department of Physics, Joseph Henry Laboratories, Princeton University, Princeton, New Jersey 08544 (United States); Wilczek, F. [School of Natural Sciences, Institute for Advanced Study, Olden Lane, Princeton, New Jersey 08540 (United States)] [School of Natural Sciences, Institute for Advanced Study, Olden Lane, Princeton, New Jersey 08540 (United States)

1996-11-01

153

Neutron electric form factor via recoil polarimetry

The ratio of the electric to the magnetic form factor of the neutron, G_En/G_Mn, was measured via recoil polarimetry from the quasielastic d({pol-e},e'{pol-n)p reaction at three values of Q^2 [viz., 0.45, 1.15 and 1.47 (GeV/c)^2] in Hall C of the Thomas Jefferson National Accelerator Facility. Preliminary data indicate that G_En follows the Galster parameterization up to Q^2 = 1.15 (GeV/c)^2 and appears to rise above the Galster parameterization at Q^2 = 1.47 (GeV/c)^2.

Richard Madey; Andrei Semenov; Simon Taylor; Aram Aghalaryan; Erick Crouse; Glen MacLachlan; Bradley Plaster; Shigeyuki Tajima; William Tireman; Chenyu Yan; Abdellah Ahmidouch; Brian Anderson; Razmik Asaturyan; O. Baker; Alan Baldwin; Herbert Breuer; Roger Carlini; Michael Christy; Steve Churchwell; Leon Cole; Samuel Danagoulian; Donal Day; Mostafa Elaasar; Rolf Ent; Manouchehr Farkhondeh; Howard Fenker; John Finn; Liping Gan; Kenneth Garrow; Paul Gueye; Calvin Howell; Bitao Hu; Mark Jones; James Kelly; Cynthia Keppel; Mahbubul Khandaker; Wooyoung Kim; Stanley Kowalski; Allison Lung; David Mack; D. Manley; Pete Markowitz; Joseph Mitchell; Hamlet Mkrtchyan; Allena Opper; Charles Perdrisat; Vina Punjabi; Brian Raue; Tilmann Reichelt; Joerg Reinhold; Julie Roche; Yoshinori Sato; Wonick Seo; Neven Simicevic; Gregory Smith; Samuel Stepanyan; Vardan Tadevosyan; Liguang Tang; Paul Ulmer; William Vulcan; John Watson; Steven Wells; Frank Wesselmann; Stephen Wood; Chen Yan; Seunghoon Yang; Lulin Yuan; Wei-Ming Zhang; Hong Guo Zhu; Xiaofeng Zhu

2003-05-01

154

Universal Binding and Recoil Corrections to Bound State g Factors in Hydrogenlike Ions

The leading relativistic and recoil corrections to bound state g factors of particles with arbitrary spin are calculated. It is shown that these corrections are universal for any spin and depend only on the free particle gyromagnetic ratios. To prove this universality we develop nonrelativistic quantum electrodynamics (NRQED) for charged particles with an arbitrary spin. The coefficients in the NRQED Hamiltonian for higher spin particles are determined only by the requirements of Lorentz invariance and local charge conservation in the respective relativistic theory. For spin one charged particles, the NRQED Hamiltonian follows from the renormalizable QED of the charged vector bosons. We show that universality of the leading relativistic and recoil corrections can be explained with the help of the Bargmann-Michael-Telegdi equation.

Eides, Michael I.; Martin, Timothy J. S. [Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506 (United States)

2010-09-03

155

We consider a model of an optical cavity with a nonequilibrium reservoir consisting of a beam of identical two-level atom pairs (TLAPs) in the general X-state. We find that coherence of multiparticle nonequilibrium reservoir plays a central role on the potential work capability of cavity. We show that no matter whether there are quantum correlations in each TLAP (including quantum entanglement and quantum discord) or not the coherence of the TLAPs has an effect on the work capability of the cavity. Additionally, constructive and destructive interferences could be induced to influence the work capability of cavity only by adjusting the relative phase with which quantum correlations have nothing to do. In this paper, the coherence of reservoir rather than the quantum correlations effectively reflecting the effects of reservoir on the system's work capability is demonstrated clearly.

Hai Li; Jian Zou; Wen-Li Yu; Bao-Ming Xu; Jun-Gang Li; Bin Shao

2014-05-12

156

Optimal tunneling enhances the quantum photovoltaic effect in double quantum dots

NASA Astrophysics Data System (ADS)

We investigate the quantum photovoltaic effect in double quantum dots by applying the nonequilibrium quantum master equation. A drastic suppression of the photovoltaic current is observed near the open circuit voltage, which leads to a large filling factor. We find that there always exists an optimal inter-dot tunneling that significantly enhances the photovoltaic current. Maximal output power will also be obtained around the optimal inter-dot tunneling. Moreover, the open circuit voltage behaves approximately as the product of the eigen-level gap and the Carnot efficiency. These results suggest a great potential for double quantum dots as efficient photovoltaic devices.

Wang, Chen; Ren, Jie; Cao, Jianshu

2014-04-01

157

Effective fault-tolerant quantum computation with slow measurements

How important is fast measurement for fault-tolerant quantum computation? Using a combination of existing and new ideas, we argue that measurement times as long as even 1,000 gate times or more have a very minimal effect on the quantum accuracy threshold. This shows that slow measurement, which appears to be unavoidable in many implementations of quantum computing, poses no essential obstacle to scalability.

David P. DiVincenzo; Panos Aliferis

2006-08-03

158

On Quantum Effects in a Theory of Biological Evolution

We construct a descriptive toy model that considers quantum effects on biological evolution starting from Chaitin's classical framework. There are smart evolution scenarios in which a quantum world is as favorable as classical worlds for evolution to take place. However, in more natural scenarios, the rate of evolution depends on the degree of entanglement present in quantum organisms with respect to classical organisms. If the entanglement is maximal, classical evolution turns out to be more favorable. PMID:22413059

Martin-Delgado, M. A.

2012-01-01

159

Synchrotron-radiation experiments with recoil ions

Studies of atoms, ions and molecules with synchrotron radiation have generally focused on measurements of properties of the electrons ejected during, or after, the photoionization process. Much can also be learned, however, about the atomic or molecular relaxation process by studies of the residual ions or molecular fragments following inner-shell photoionization. Measurements are reported of mean kinetic energies of highly charged argon, krypton, and xenon recoil ions produced by vacancy cascades following inner-shell photoionization using white and monochromatic synchrotron x radiation. Energies are much lower than for the same charge-state ions produced by charged-particle impact. The results may be applicable to design of future angle-resolved ion-atom collision experiments. Photoion charge distributions are presented and compared with other measurements and calculations. Related experiments with synchrotron-radiation produced recoil ion, including photoionization of stored ions and measurement of shakeoff in near-threshold excitation, are briefly discussed. 24 refs., 6 figs., 1 tab.

Levin, J.C.

1989-01-01

160

Quantum anomalous Hall effect in magnetically doped InAs/GaSb quantum wells.

The quantum anomalous Hall effect has recently been observed experimentally in thin films of Cr-doped (Bi,Sb)(2)Te(3) at a low temperature (? 30 mK). In this work, we propose realizing the quantum anomalous Hall effect in more conventional diluted magnetic semiconductors with magnetically doped InAs/GaSb type-II quantum wells. Based on a four-band model, we find an enhancement of the Curie temperature of ferromagnetism due to band edge singularities in the inverted regime of InAs/GaSb quantum wells. Below the Curie temperature, the quantum anomalous Hall effect is confirmed by the direct calculation of Hall conductance. The parameter regime for the quantum anomalous Hall phase is identified based on the eight-band Kane model. The high sample quality and strong exchange coupling make magnetically doped InAs/GaSb quantum wells good candidates for realizing the quantum anomalous Hall insulator at a high temperature. PMID:25325653

Wang, Qing-Ze; Liu, Xin; Zhang, Hai-Jun; Samarth, Nitin; Zhang, Shou-Cheng; Liu, Chao-Xing

2014-10-01

161

Observation of quantum effects and Coulomb blockade in silicon quantum-dot transistors of lithographically defined nanoscale silicon quantum-dot transistors that operate at temperatures over 100 K semiconductors instead of Si--the backbone material of the integrated circuit IC industry. To make the quantum

162

Quantum Hall effect in gapped graphene heterojunctions

NASA Astrophysics Data System (ADS)

We model the quantum Hall effect in heterostructures made of two gapped graphene stripes with different gaps, ?1 and ?2. We consider two main situations, ?1=0,?2?0, and ?1=-?2. They are different in a fundamental aspect: only the latter features kink states that, when intervalley coupling is absent, are protected against backscattering. We compute the two-terminal conductance of heterostructures with channel length up to 430 nm, in two transport configurations, parallel and perpendicular to the interface. By studying the effect of disorder on the transport along the boundary, we quantify the robustness of kink states with respect to backscattering. Transport perpendicular to the boundary shows how interface states open a backscattering channel for the conducting edge states, spoiling the perfect conductance quantization featured by the homogeneously gapped graphene Hall bars. Our results can be relevant for the study of graphene deposited on hexagonal boron-nitride, as well as to model graphene with an interaction-driven gapped phase with two equivalent phases separated by a domain wall.

Lado, J. L.; González, J. W.; Fernández-Rossier, J.

2013-07-01

163

Cancer proliferation and therapy: the Warburg effect and quantum metabolism

BACKGROUND: Most cancer cells, in contrast to normal differentiated cells, rely on aerobic glycolysis instead of oxidative phosphorylation to generate metabolic energy, a phenomenon called the Warburg effect. MODEL: Quantum metabolism is an analytic theory of metabolic regulation which exploits the methodology of quantum mechanics to derive allometric rules relating cellular metabolic rate and cell size. This theory explains differences

Lloyd A. Demetrius; Johannes F. Coy; Jack A. Tuszynski

2010-01-01

164

Controlling ac losses in quantum Hall effect devices

When measured with ac at kilohertz frequencies the quantized Hall resistance (QHR) of a quantum Hall effect (QHE) device is usually found to be current- and frequency-dependent. This is a limitation on its use as a quantum impedance standard. We develop a model for the principal ac losses arising in the QHE device and show how they are responsible for

F. Delahaye; B. P. Kibble; A. Zarka

2000-01-01

165

Quantum nuclear effects on surfaces and dispersion bonded systems

Quantum nuclear effects on surfaces and dispersion bonded systems Erlend Davidson A dissertation model systems. By comparing with experiment whenever possible we provide new insight into how quantum . . . . . . . . . . . . 18 2.2 Born-Oppenheimer approximation . . . . . . . . . . . . . . . . . . 19 2.3 Density functional

Guillas, Serge

166

THE NEW HRIBF RECOIL MASS SPECTROMETER | PERFORMANCE AND FIRST RESULTS

than 15 years recoil mass spectrometers have served as an important tool for nuclear structure and decay studies. This dissertation documents the newest addition to the family of these devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii Chapter I. THE ROLE OF RECOIL MASS SPECTROMETERS IN NUCLEAR SPECTROSCOPY 1 Nuclear Structure

167

Vibrational Spectra Including Critical Nuclear Quantum Effects Isaiah Sumner and Srinivasan S. Iyengar to study vibrational spectroscopy in clusters inclusive of critical nuclear quantum effects. This approach the vibrational density of states of [Cl-H-Cl]- , inclusive of critical quantum nuclear effects, and our results

Iyengar, Srinivasan S.

168

Memory effects in quantum channel discrimination

We consider quantum-memory assisted protocols for discriminating quantum channels. We show that for optimal discrimination of memory channels, memory assisted protocols are needed. This leads to a new notion of distance for channels with memory. For optimal discrimination and estimation of sets of unitary channels memory-assisted protocols are not required.

Giulio Chiribella; Giacomo M. D'Ariano; Paolo Perinotti

2008-03-21

169

Recoil alignment in muon capture on {sup 14}N

We report a measurement of the longitudinal alignment A{sub L} of the recoil nucleus in the {mu}{sup -}+{sup 14}N(1{sup +},0){yields}{nu}{sub {mu}}+{sup 14}C(2{sup +},7012) transition. The experiment was performed on the M9B beamline at the TRIUMF cyclotron via the measurement of the Doppler line shape of the subsequent {sup 14}C(2{sup +},7012){yields}{sup 14}C(0{sup +},0) {gamma} rays. We compare our result, A{sub L}=0.60{+-}0.11, to various model calculations and discuss the sensitivity to the induced pseudoscalar coupling, second-forbidden effects, and 2({Dirac_h}/2{pi}){omega} wave-function admixtures.

Gorringe, T.P.; Corbin, D.P. [University of Kentucky, Lexington, Kentucky 40506 (United States); Stocki, T.J. [University of British Columbia, Vancouver, British Columbia, V6T 1Z1 (Canada)

2005-03-01

170

Quantum Spin Hall Effect in Inverted Type II Semiconductors

The quantum spin Hall (QSH) state is a topologically non-trivial state of quantum matter which preserves time-reversal symmetry; it has an energy gap in the bulk, but topologically robust gapless states at the edge. Recently, this novel effect has been predicted and observed in HgTe quantum wells. In this work we predict a similar effect arising in Type-II semiconductor quantum wells made from InAs/GaSb/AlSb. Because of a rare band alignment the quantum well band structure exhibits an 'inverted' phase similar to CdTe/HgTe quantum wells, which is a QSH state when the Fermi level lies inside the gap. Due to the asymmetric structure of this quantum well, the effects of inversion symmetry breaking and inter-layer charge transfer are essential. By standard self-consistent calculations, we show that the QSH state persists when these corrections are included, and a quantum phase transition between the normal insulator and the QSH phase can be electrically tuned by the gate voltage.

Liu, Chaoxing; /Tsinghua U., Beijing /Stanford U., Phys. Dept.; Hughes, Taylor L.; Qi, Xiao-Liang; /Stanford U., Phys. Dept.; Wang, Kang; /UCLA; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

2010-03-19

171

Monte Carlo simulation of quantum Zeno effect in the brain

Environmental decoherence appears to be the biggest obstacle for successful construction of quantum mind theories. Nevertheless, the quantum physicist Henry Stapp promoted the view that the mind could utilize quantum Zeno effect to influence brain dynamics and that the efficacy of such mental efforts would not be undermined by environmental decoherence of the brain. To address the physical plausibility of Stapp's claim, we modeled the brain using quantum tunneling of an electron in a multiple-well structure such as the voltage sensor in neuronal ion channels and performed Monte Carlo simulations of quantum Zeno effect exerted by the mind upon the brain in the presence or absence of environmental decoherence. The simulations unambiguously showed that the quantum Zeno effect breaks down for timescales greater than the brain decoherence time. To generalize the Monte Carlo simulation results for any n-level quantum system, we further analyzed the change of brain entropy due to the mind probing actions and proved a theorem according to which local projections cannot decrease the von Neumann entropy of the unconditional brain density matrix. The latter theorem establishes that Stapp's model is physically implausible but leaves a door open for future development of quantum mind theories provided the brain has a decoherence-free subspace.

Danko Georgiev

2014-12-11

172

Nuclear recoil scintillation and ionisation yields in liquid xenon from ZEPLIN-III data

Scintillation and ionisation yields for nuclear recoils in liquid xenon above 10 keVnr (nuclear recoil energy) are deduced from data acquired using broadband Am-Be neutron sources. The nuclear recoil data from several exposures to two sources were compared to detailed simulations. Energy-dependent scintillation and ionisation yields giving acceptable fits to the data were derived. Efficiency and resolution effects are treated using a light collection Monte Carlo, measured photomultiplier response profiles and hardware trigger studies. A gradual fall in scintillation yield below ~40 keVnr is found, together with a rising ionisation yield; both are in good agreement with the latest independent measurements. The analysis method is applied to both the most recent ZEPLIN-III data, acquired with a significantly upgraded detector and a precision-calibrated Am-Be source, as well as to the earlier data from the first run in 2008. A new method for deriving the recoil scintillation yield, which includes sub-threshold S1 events, is also presented which confirms the main analysis.

M. Horn; V. A. Belov; D. Yu. Akimov; H. M. Araújo; E. J. Barnes; A. A. Burenkov; V. Chepel; A. Currie; B. Edwards; C. Ghag; A. Hollingsworth; G. E. Kalmus; A. S. Kobyakin; A. G. Kovalenko; V. N. Lebedenko; A. Lindote; M. I. Lopes; R. Lüscher; P. Majewski; A. StJ. Murphy; F. Neves; S. M. Paling; J. Pinto da Cunha; R. Preece; J. J. Quenby; L. Reichhart; P. R. Scovell; C. Silva; V. N. Solovov; N. J. T. Smith; P. F. Smith; V. N. Stekhanov; T. J. Sumner; C. Thorne; L. de Viveiros; R. J. Walker

2011-06-03

173

Recoil and Stiffening by Adherent Leukocytes in Response to Fluid Shear?

Abstract Prolonged exposure to fluid shear stress alters leukocyte functions associated with the immune response. We examined the initial response of freshly isolated human leukocytes to fluid shear stress under high magnification. Adherent leukocytes exhibit a rapid biomechanical response to physiological levels of fluid shear stress. After passive displacement in the direction of a constant fluid shear stress, adherent leukocytes actively recoil back in the opposite direction of the fluid flow. Recoil is observed within seconds of the applied fluid shear stress. Simultaneously, fluid shear stress induces a stiffening of the cell. The immediate cell displacement in response to a step increase in fluid shear stress is greatly attenuated in subsequent steps compared to the initial fluid shear stress step. Recoil is not mediated by actin polymerization-dependent mechanisms, as cytochalasin D had no effect on this early response. However, stiffening was determined in part by an intact actin cytoskeleton. Inhibiting myosin force generation with ML-7 abolished the recoil and stiffening responses, implicating force generation by myosin as an important contributor to the early leukocyte response to fluid shear stress. This initial shear stress response may be particularly important in facilitating leukocyte attachment under sustained fluid shear stress by the flowing blood in the microcirculation. PMID:17921217

Coughlin, Mark F.; Sohn, David D.; Schmid-Schönbein, Geert W.

2008-01-01

174

Octet Quantum Hall Effect in Graphene Bilayers

NASA Astrophysics Data System (ADS)

Interaction driven integer quantum Hall effects are anticipated [1]in graphene bilayers because of the near-degeneracy of eight Landau levels which appear near the neutral system Fermi level at filling factors between ?=-4 and ?=4. The bilayer graphene octet exhibtits a wide variety of broken symmetry states, with Ising, XY and Heisenberg character which can be controlled by an external field which creates an electric potential difference between the two layers. Because of the peculiarities of the bilayer graphene electronic structure states with n=0 and n=1 orbital character are degenerate. I will explain predictions that an intra-Landau-level cyclotron resonance signal will appear at some odd-integer filling factors, accompanied by collective modes which are nearly gapless and have approximate k^3/2 dispersion. This talk will be based on work performed in collaboration with Yafis Barlas, Rene Cote, Kentaro Nomura, and Jules Lambert. [4pt] [1] Y. Barlas et al. , Phys. Rev. Lett. 101, 097601(2008).

MacDonald, Allan H.

2009-03-01

175

A proton recoil telescope for neutron spectroscopy

NASA Astrophysics Data System (ADS)

A new proton recoil telescope (PRT) detector is presented: it is composed by an active multilayer of segmented plastic scintillators as neutron to proton converter, by two silicon strip detectors and by a final thick CsI(Tl) scintillator. The PRT can be used to measure neutron spectra in the range 2-160 MeV. The detector characteristics have been studied in detail with the help of Monte Carlo simulations. The overall energy resolution of the system ranges from about 20% at the lowest neutron energy to about 2% at 160 MeV. The global efficiency is about 3×10-5. Experimental tests have been performed by using the reaction 13C(d,n) at 40 MeV deuteron energy.

Donzella, A.; Barbui, M.; Bocci, F.; Bonomi, G.; Cinausero, M.; Fabris, D.; Fontana, A.; Giroletti, E.; Lunardon, M.; Moretto, S.; Nebbia, G.; Necchi, M. M.; Pesente, S.; Prete, G.; Rizzi, V.; Viesti, G.; Zenoni, A.

2010-01-01

176

Two quantum effects in the theory of gravitation

We will discuss two methods by which the formalism of quantum field theory can be included in calculating the physical effects of gravitation. In the first of these, the consequences of treating general relativity as an ...

Robinson, Sean Patrick, 1977-

2005-01-01

177

Imaging transport resonances in the quantum Hall effect

We image charge transport in the quantum Hall effect using a scanning charge accumulation microscope. Applying a DC bias voltage to the tip induces a highly resistive ring-shaped incompressible strip (IS) in a very high ...

Steele, Gary Alexander

2006-01-01

178

NASA Astrophysics Data System (ADS)

An innovative method has been demonstrated for separating alpha-emitting isotopes for medical radiotherapy applications. The method relies on recoil-ion separation rather than on conventional wet chemistry techniques to separate medical isotopes from their precursor sources. The isotopes 225Ac and 213Bi have been separated from electro-deposited sources of 229ThO 2. Separations of 225Ac were carried out by placing nickel recoil collector foils in firm contact with the 229ThO 2 sources. One-stage recoil-ion separations of 225Ac from 229Th have been performed as well as two-stage separations of 213Bi from previously recoil separated 225Ac. In addition, a direct recoil separation of 213Bi from 229Th has been demonstrated. The 213Bi from the one-stage direct separation has a high isotopic purity, but contains small amounts of long-lived 225Ac alpha activity. The two-stage separations of 213Bi produce high isotopic purity material (>99.9999%), but result in lower isotopic yields. Range-energy calculations have been carried out to determine the yields of recoil ions as a function of alpha-particle energy and ThO 2 thickness. The results of the calculations have been benchmarked with recoil separation measurements carried out using ThO 2 electro-deposits over a range of thickness. A computer code based on the generalized Bateman equations has been developed to allow calculations of the amounts of any isotope in the 229Th decay chain as a function of recoil separation exposure time and elapsed time after the separation. An excellent match has been obtained between the predictions of the Bateman calculations and the results of recoil separation measurements. The recoil separation method has proven to be a simple and effective way of separating medically useful isotopes such as 213Bi. In addition, the method has been shown to produce no chemical or radioactive wastes, in contrast to radiochemical separation methods, which generate mixed (chemical and radioactive) waste.

Ruddy, F. H.; Dulloo, A. R.; Seidel, J. G.; Petrovi?, B.

2004-01-01

179

Can Quantum Gravitational Effects Manifest themselves at Large Distances?

Consider a proposed model of the universe with $\\hbar$ much greater than its well-known value of $10^{-34} Js$. In this model universe, very large objects can show quantum behaviors. In a scenario with large extra dimensions, $\\hbar$ can attains very large values depending on the dimensionality of spacetime. In this letter, we show that although conventional thinking indicates that quantum gravitational effects should manifest themselves only at very small scales, in actuality quantum gravitational effects can manifest themselves at large scales too. We use the generalized uncertainty principle with a non-zero minimal uncertainty in momentum as our primary input to construct a mathematical framework for our proposal.

Kourosh Nozari; Behnaz Fazlpour

2006-07-02

180

Complex scattering dynamics and the quantum Hall effects

We review both classical and quantum potential scattering in two dimensions in a magnetic field, with applications to the quantum Hall effect. Classical scattering is complex, due to the approach of scattering states to an infinite number of dynamically bound states. Quantum scattering follows the classical behavior rather closely, exhibiting sharp resonances in place of the classical bound states. Extended scatterers provide a quantitative explanation for the breakdown of the QHE at a comparatively small Hall voltage as seen by Kawaji et al., and possibly for noise effects.

Trugman, S.A.

1994-12-16

181

Planck scale effects on some low energy quantum phenomena

NASA Astrophysics Data System (ADS)

Almost all theories of Quantum Gravity predict modifications of the Heisenberg Uncertainty Principle near the Planck scale to a so-called Generalized Uncertainty Principle (GUP). Recently it was shown that the GUP gives rise to corrections to the Schrödinger and Dirac equations, which in turn affect all non-relativistic and relativistic quantum Hamiltonians. In this Letter, we apply it to superconductivity and the quantum Hall effect and compute Planck scale corrections. We also show that Planck scale effects may account for a (small) part of the anomalous magnetic moment of the muon. We obtain (weak) empirical bounds on the undetermined GUP parameter from present-day experiments.

Das, Saurya; Mann, R. B.

2011-10-01

182

Spacetime effects on satellite-based quantum communications

We investigate the effects of space-time curvature on space-based quantum communication protocols. We analyze tasks that require either the exchange of single photons in a certain entanglement distribution protocol or beams of light in a continuous-variable quantum key distribution scheme. We find that gravity affects the propagation of photons, therefore acting as a noisy channel for the transmission of information. The effects can be measured with current technology.

Bruschi, David Edward; Fuentes, Ivette; Jennewein, Thomas; Razavi, Mohsen

2013-01-01

183

The modulational instability of quantum electrostatic acoustic waves in electron-hole quantum semiconductor plasmas is investigated using the quantum hydrodynamic model, from which a modified nonlinear Schrödinger equation with damping effects is derived using the reductive perturbation method. Here, we consider the combined effects of quantum recoil, quantum degenerate pressures, as well as the exchange-correlation effect standing for the electrons (holes) spin. The modulational instability for different semiconductors (GaAs, GaSb, and InP) is discussed. The collision between electron (hole) and phonon is also investigated. The permitted maximum time for modulational instability and the damping features of quantum envelope solitary wave are all determined by the collision. The approximate solitary solution with damping effects is presented in weak collision limit. The damping properties were discussed by numerical method.

Wang, Yunliang, E-mail: ylwang@ustb.edu.cn; Lü, Xiaoxia [Department of Physics, School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083 (China)] [Department of Physics, School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083 (China)

2014-02-15

184

NASA Astrophysics Data System (ADS)

The modulational instability of quantum electrostatic acoustic waves in electron-hole quantum semiconductor plasmas is investigated using the quantum hydrodynamic model, from which a modified nonlinear Schrödinger equation with damping effects is derived using the reductive perturbation method. Here, we consider the combined effects of quantum recoil, quantum degenerate pressures, as well as the exchange-correlation effect standing for the electrons (holes) spin. The modulational instability for different semiconductors (GaAs, GaSb, and InP) is discussed. The collision between electron (hole) and phonon is also investigated. The permitted maximum time for modulational instability and the damping features of quantum envelope solitary wave are all determined by the collision. The approximate solitary solution with damping effects is presented in weak collision limit. The damping properties were discussed by numerical method.

Wang, Yunliang; Lü, Xiaoxia

2014-02-01

185

Objectives Cardiovascular magnetic resonance feature tracking (CMR-FT) offers quantification of myocardial deformation from routine cine images. However, data using CMR-FT to quantify left ventricular (LV) torsion and diastolic recoil are not yet available. We therefore sought to evaluate the feasibility and reproducibility of CMR-FT to quantify LV torsion and peak recoil rate using an optimal anatomical approach. Methods Short-axis cine stacks were acquired at rest and during dobutamine stimulation (10 and 20 µg·kg?1·min?1) in 10 healthy volunteers. Rotational displacement was analysed for all slices. A complete 3D-LV rotational model was developed using linear interpolation between adjacent slices. Torsion was defined as the difference between apical and basal rotation, divided by slice distance. Depending on the distance between the most apical (defined as 0% LV distance) and basal (defined as 100% LV distance) slices, four different models for the calculation of torsion were examined: Model-1 (25–75%), Model-2 (0–100%), Model-3 (25–100%) and Model-4 (0–75%). Analysis included subendocardial, subepicardial and global torsion and recoil rate (mean of subendocardial and subepicardial values). Results Quantification of torsion and recoil rate was feasible in all subjects. There was no significant difference between the different models at rest. However, only Model-1 (25–75%) discriminated between rest and stress (Global Torsion: 2.7±1.5°cm?1, 3.6±2.0°cm?1, 5.1±2.2°cm?1, p<0.01; Global Recoil Rate: ?30.1±11.1°cm?1s?1,?46.9±15.0°cm?1s?1,?68.9±32.3°cm?1s?1, p<0.01; for rest, 10 and 20 µg·kg?1·min?1 of dobutamine, respectively). Reproducibility was sufficient for all parameters as determined by Bland-Altman analysis, intraclass correlation coefficients and coefficient of variation. Conclusions CMR-FT based derivation of myocardial torsion and recoil rate is feasible and reproducible at rest and with dobutamine stress. Using an optimal anatomical approach measuring rotation at 25% and 75% apical and basal LV locations allows effective quantification of torsion and recoil dynamics. Application of these new measures of deformation by CMR-FT should next be explored in disease states. PMID:25285656

Hussain, Shazia T.; Kutty, Shelby; Steinmetz, Michael; Sohns, Jan M.; Fasshauer, Martin; Staab, Wieland; Unterberg-Buchwald, Christina; Bigalke, Boris; Lotz, Joachim; Hasenfuß, Gerd; Schuster, Andreas

2014-01-01

186

Quantum-Memory Effects in the Emission of Quantum-Dot Microcavities

NASA Astrophysics Data System (ADS)

The experimentally measured input-output characteristics of optically pumped semiconductor microcavities exhibits unexpected oscillations modifying the fundamentally linear slope in the excitation power regime below lasing. A systematic microscopic analysis reproduces these oscillations, identifying them as a genuine quantum-memory effect, i.e., a photon-density correlation accumulated during the excitation. With the use of projected quantum measurements, it is shown that the input-output oscillations can be controlled and enhanced by an order of magnitude when the quantum fluctuations of the pump are adjusted.

Berger, C.; Huttner, U.; Mootz, M.; Kira, M.; Koch, S. W.; Tempel, J.-S.; Aßmann, M.; Bayer, M.; Mintairov, A. M.; Merz, J. L.

2014-08-01

187

Quantum-confined strain gradient effect in semiconductor nanomembranes

NASA Astrophysics Data System (ADS)

Semiconductor nanomembranes can exhibit strain gradients that lead to quantum confinement effects similar to the well known quantum-confined Stark effect (QCSE) in semiconductor quantum wells. The deformation of square well into triangular well potential leads to modifications of the exciton resonance, but important differences between the quantum-confined strain gradient effect (QCsgE) and the QCSE include (i) the versatility of the QCsgE in which conduction and valence bands can have different slopes (even reverse slopes are possible), and (ii) the fact that in the QCsgE exciton shifts are determined by the gradients in the heavy-hole and light-hole energies as well as a gradient in the heavy-hole and light-hole coupling.

Binder, R.; Gu, B.; Kwong, N. H.

2014-11-01

188

Characterization of control noise effects in optimal quantum unitary dynamics

NASA Astrophysics Data System (ADS)

This work develops measures for quantifying the effects of field noise upon targeted unitary transformations. Robustness to noise is assessed in the framework of the quantum control landscape, which is the mapping from the control to the unitary transformation performance measure (quantum gate fidelity). Within that framework, a geometric interpretation of stochastic noise effects naturally arises, where more robust optimal controls are associated with regions of small overlap between landscape curvature and the noise correlation function. Numerical simulations of this overlap in the context of quantum information processing reveal distinct noise spectral regimes that better support robust control solutions. This perspective shows the dual importance of both noise statistics and the control form for robustness, thereby opening up new avenues of investigation on how to mitigate noise effects in quantum systems.

Hocker, David; Brif, Constantin; Grace, Matthew D.; Donovan, Ashley; Ho, Tak-San; Tibbetts, Katharine Moore; Wu, Rebing; Rabitz, Herschel

2014-12-01

189

Impurity position effect on optical properties of various quantum dots

NASA Astrophysics Data System (ADS)

In this work, we have investigated the effect of impurity position on optical properties of a pyramid and a cone like quantum dot. For this goal, we first obtain the energy levels and wave functions using finite element method (FEM) in the presence of impurity. Then, we have studied the influence of impurity location on refractive index changes and absorption coefficients of the two quantum dots. We found that there is a maximum value for total refractive index changes and absorption coefficients at a special impurity position. Also, we have found that the refractive index changes and absorption coefficients of a cone like quantum dot are greater than a pyramid quantum dot in same volume and height. According to the results, it is deduced that the impurity location plays an important and considerable role in the electronic and optical properties of a pyramid and a cone like quantum dot.

Khordad, R.; Bahramiyan, H.

2015-02-01

190

Huge Quantum Gravity Effects in the Solar System

Normally one thinks of the motion of the planets around the Sun as a highly classical phenomenon, so that one can neglect quantum gravity in the Solar System. However, classical chaos in the planetary motion amplifies quantum uncertainties so that they become very large, giving huge quantum gravity effects. For example, evidence suggests that Uranus may eventually be ejected from the Solar System, but quantum uncertainties would make the direction at which it leaves almost entirely uncertain, and the time of its exit uncertain by about a billion billion years. For a time a billion billion years from now, there are huge quantum uncertainties whether Uranus will be within the Solar System, within the Galaxy, or even within causal contact of the Galaxy.

Don N. Page

2010-05-17

191

Theory of ionizing neutrino-atom collisions: The role of atomic recoil

We consider theoretically ionization of an atom by neutrino impact taking into account electromagnetic interactions predicted for massive neutrinos by theories beyond the Standard Model. The effects of atomic recoil in this process are estimated using the one-electron and semiclassical approximations and are found to be unimportant unless the energy transfer is very close to the ionization threshold. We show that the energy scale where these effects become important is insignificant for current experiments searching for magnetic moments of reactor antineutrinos.

Konstantin A. Kouzakov; Alexander I. Studenikin

2014-11-09

192

NASA Astrophysics Data System (ADS)

The effect of the Coriolis interaction upon the sharing of energy between rotational and vibrational excitation during an electronic transition is considered with particular emphasis on recoil-induced excitation during photoionization. If there is a large change in equilibrium bond length upon ionization, then Coriolis coupling leads to a significant transfer of energy between rotational and vibrational excitation. Experimental results for valence ionization of N2 and CO and for carbon 1 s ionization of CO show evidence of this effect.

Thomas, T. Darrah

2014-11-01

193

Modeling the Observability of Recoiling Black Holes as Offset Quasars

NASA Astrophysics Data System (ADS)

The merger of two supermassive black holes (SMBHs) imparts a gravitational-wave (GW) recoil kick to the remnant SMBH. In extreme cases these kicks may be thousands of km/s -- enough to easily eject them from their host galaxies. Moderate recoil kicks may also cause substantial displacements of the SMBH, however. An actively-accreting, recoiling SMBH may be observable as an offset quasar. Prior to the advent of a space-based GW observatory, detections of these offset quasars may offer the best chance for identifying recent SMBH mergers. Indeed, observational searches for recoiling quasars have already identified several promising candidates. However, systematic searches for recoils are currently hampered by large uncertainties regarding how often offset quasars should be observable, where they are most likely to be found, and whether BH spin alignment prior to merger is efficient at suppressing large recoils. Motivated by this, we have developed a model for the observable population of recoiling quasars in a cosmological framework, utilizing detailed information about the progenitor galaxies from state-of-the-art cosmological hydrodynamic simulations (the Illustris Project). The model for offset quasar lifetimes includes a physically-motivated, time-dependent model for accretion onto kicked SMBHs, and results are analyzed for a range of possible BH spin alignment models. We find that the observability of offset quasars depends strongly on the efficiency of pre-merger spin alignment, with promising indications that observations of recoils could distinguish between at least the extreme limits of spin alignment models. Our results also suggest that observable offset quasars should inhabit preferred types of host galaxies, where again these populations depend on the degree of pre-merger spin alignment. These findings will be valuable for planned and future dedicated searches for recoiling quasars, and they indicate that such objects might be used to place indirect constraints on SMBH spins.

Blecha, Laura; Torrey, Paul Adam; Vogelsberger, Mark; Genel, Shy; Springel, Volker; Sijacki, Debora; Snyder, Greg; Bird, Simeon; Nelson, Dylan R.; Xu, Dandan; Hernquist, Lars E.

2015-01-01

194

Effective Theories of Coupled Classical and Quantum Variables

We address the issue of coupling variables which are essentially classical to variables that are quantum. Two approaches are discussed. In the first (based on collaborative work with L.Di\\'osi), continuous quantum measurement theory is used to construct a phenomenological description of the interaction of a quasiclassical variable $X$ with a quantum variable $x$, where the quasiclassical nature of $X$ is assumed to have come about as a result of decoherence. The state of the quantum subsystem evolves according to the stochastic non-linear Schr\\"odinger equation of a continuously measured system, and the classical system couples to a stochastic c-number $\\x (t)$ representing the imprecisely measured value of $x$. The theory gives intuitively sensible results even when the quantum system starts out in a superposition of well-separated localized states. The second approach involves a derivation of an effective theory from the underlying quantum theory of the combined quasiclassical--quantum system, and uses the decoherent histories approach to quantum theory.

J. J. Halliwell

1998-08-26

195

Aharonov-Bohm Effect: a Quantum Variation and Classical Analogy

In this work we consider a quantum variation of the usual Aharonov-Bohm effect with two solenoids sufficiently close one to the other so that (external) electron cannot propagate between two solenoids but only around both solenoids. Here magnetic field (or classical vector potential of the electromagnetic field) acting at quantum propagating (external) electron represents the quantum mechanical average value or statistical mixture. It is obtained by wave function of single (internal, quantum propagating within some solenoid wire) electron (or homogeneous ensemble of such (internal) electrons) representing a quantum superposition with two practically non-interfering terms. All this implies that phase difference and interference shape translation of the quantum propagating (external) electron represent the quantum mechanical average value or statistical mixture. On the other hand we consider a classical analogy and variation of the usual Aharonov-Bohm effect in which Aharonov-Bohm solenoid is used for the primary coil inside secondary large coil in the remarkable classical Faraday experiment of the electromagnetic induction.

Vladan Pankovic; Darko Kapor; Stevica Djurovic; Milan Pantic

2014-04-23

196

Anomalous and Quantum Hall Effects in Lossy Photonic Lattices

NASA Astrophysics Data System (ADS)

We theoretically discuss analogues of the anomalous and the integer quantum Hall effect in driven-dissipative two-dimensional photonic lattices in the presence of a synthetic gauge field. Photons are coherently injected by a spatially localized pump, and the transverse shift of the in-plane light distribution under the effect of an additional uniform force is considered. Depending on pumping parameters, the transverse shift turns out to be proportional either to the global Chern number (integer quantum Hall effect) or to the local Berry curvature (anomalous Hall effect). This suggests a viable route to experimentally measure these quantities in photonic lattices.

Ozawa, Tomoki; Carusotto, Iacopo

2014-04-01

197

Anomalous and quantum Hall effects in lossy photonic lattices.

We theoretically discuss analogues of the anomalous and the integer quantum Hall effect in driven-dissipative two-dimensional photonic lattices in the presence of a synthetic gauge field. Photons are coherently injected by a spatially localized pump, and the transverse shift of the in-plane light distribution under the effect of an additional uniform force is considered. Depending on pumping parameters, the transverse shift turns out to be proportional either to the global Chern number (integer quantum Hall effect) or to the local Berry curvature (anomalous Hall effect). This suggests a viable route to experimentally measure these quantities in photonic lattices. PMID:24745421

Ozawa, Tomoki; Carusotto, Iacopo

2014-04-01

198

Effects of Loss and Decoherence on a Simple Quantum Computer

We investigate the impact of loss (amplitude damping) and decoherence (phase damping) on the performance of a simple quantum computer which solves the one-bit Deutsch problem. The components of this machine are beamsplitters and nonlinear optical Kerr cells, but errors primarily originate from the latter. We develop models to describe the effect of these errors on a quantum optical Fredkin gate. The results are used to analyze possible error correction strategies in a complete quantum computer. We find that errors due to loss can be avoided perfectly by appropriate design techniques, while decoherence can be partially dealt with using projective error correction.

Isaac L. Chuang; Raymond Laflamme; Juan-Pablo Paz

1996-02-27

199

Excitonic contributions to the quantum-confined Pockels effect

NASA Astrophysics Data System (ADS)

The quantum confined Pockels effect results from the combination of the genuine interface roto-inversion asymmetry and the breakdown of quantum well inversion symmetry due to the applied electric field. It is currently understood in terms of the field-dependent mixing of the heavy and light hole states at the center of the minizone. Here we investigate how excitonic interaction modifies the predictions of band-to-band calculations, and compare theory with experimental results obtained in InxGa1-xAs-InP quantum wells.

Toropov, A. A.; Ivchenko, E. L.; Krebs, O.; Cortez, S.; Voisin, P.; Gentner, J. L.

2001-01-01

200

Possible observational windows for quantum effects from black holes

Quantum information transfer necessary to reconcile black hole evaporation with quantum mechanics, while approximately preserving regular near-horizon geometry, can be simply parameterized in terms of couplings of the black hole internal state to quantum fields of the black hole atmosphere. The necessity of transferring sufficient information for unitarization sets the strengths of these couplings. Such couplings via the stress tensor offer apparently significant advantages, and behave like quantum fluctuations of the effective metric near the horizon. At the requisite strength, these fluctuations, while soft (low energy/momentum), have significant magnitude, and so can deflect near-horizon geodesics that span distances of order the black hole radius. Thus, the presence of such couplings can result in effects that could be detected or constrained by observation: disruption of near-horizon accretion flows, scintillation of light passing close to the black hole, and alteration of gravitational wave emission fro...

Giddings, Steven B

2014-01-01

201

The influence of the electron-exchange and quantum screening on the Thomson scattering process is investigated in degenerate quantum Fermi plasmas. The Thomson scattering cross section in quantum plasmas is obtained by the plasma dielectric function and fluctuation-dissipation theorem as a function of the electron-exchange parameter, Fermi energy, plasmon energy, and wave number. It is shown that the electron-exchange effect enhances the Thomson scattering cross section in quantum plasmas. It is also shown that the differential Thomson scattering cross section has a minimum at the scattering angle ?=?/2. It is also found that the Thomson scattering cross section increases with an increase of the Fermi energy. In addition, the Thomson scattering cross section is found to be decreased with increasing plasmon energy.

Lee, Gyeong Won [Department of Applied Physics, Hanyang University, Ansan, Kyunggi-Do 426-791 (Korea, Republic of)] [Department of Applied Physics, Hanyang University, Ansan, Kyunggi-Do 426-791 (Korea, Republic of); Jung, Young-Dae [Department of Applied Physics, Hanyang University, Ansan, Kyunggi-Do 426-791 (Korea, Republic of) [Department of Applied Physics, Hanyang University, Ansan, Kyunggi-Do 426-791 (Korea, Republic of); Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, New York 12180-3590 (United States)

2013-06-15

202

NASA Astrophysics Data System (ADS)

The influence of the electron-exchange and quantum screening on the Thomson scattering process is investigated in degenerate quantum Fermi plasmas. The Thomson scattering cross section in quantum plasmas is obtained by the plasma dielectric function and fluctuation-dissipation theorem as a function of the electron-exchange parameter, Fermi energy, plasmon energy, and wave number. It is shown that the electron-exchange effect enhances the Thomson scattering cross section in quantum plasmas. It is also shown that the differential Thomson scattering cross section has a minimum at the scattering angle ? =?/2. It is also found that the Thomson scattering cross section increases with an increase of the Fermi energy. In addition, the Thomson scattering cross section is found to be decreased with increasing plasmon energy.

Lee, Gyeong Won; Jung, Young-Dae

2013-06-01

203

Single electron charging effects in semiconductor quantum dots

We have studied charging effects in a lateral split-gate quantum dot defined by metal gates in the two dimensional electron gas (2 DEG) of a GaAs\\/AlGaAs heterostructure. The gate structure allows an independent control of the conductances of the two tunnel barriers separating the quantum dot from the two 2 DEG leads, and enables us to vary the number of

L. P. Kouwenhoven; N. C. van der Vaart; A. T. Johnson; W. Kool; C. J. P. M. Harmans; J. G. Williamson; A. A. M. Staring; C. T. Foxon

1991-01-01

204

Spacetime effects on satellite-based quantum communications

We investigate the consequences of space-time being curved on space-based quantum communication protocols. We analyze tasks that require either the exchange of single photons in a certain entanglement distribution protocol or beams of light in a continuous-variable quantum key distribution scheme. We find that gravity affects the propagation of photons, therefore adding additional noise to the channel for the transmission of information. The effects could be measured with current technology.

David Edward Bruschi; Tim Ralph; Ivette Fuentes; Thomas Jennewein; Mohsen Razavi

2013-09-12

205

Spacetime effects on satellite-based quantum communications

NASA Astrophysics Data System (ADS)

We investigate the consequences of space-time being curved on space-based quantum communication protocols. We analyze tasks that require either the exchange of single photons in a certain entanglement distribution protocol or beams of light in a continuous-variable quantum key distribution scheme. We find that gravity affects the propagation of photons, therefore adding additional noise to the channel for the transmission of information. The effects could be measured with current technology.

Bruschi, David Edward; Ralph, Timothy C.; Fuentes, Ivette; Jennewein, Thomas; Razavi, Mohsen

2014-08-01

206

Theory of Non-Adiabatic Optical Effects in Quantum Dots

Quantum dots continue to be an area of intense scientific activity, because they have a number of advantages as the `building blocks' for advanced semiconductor devices with three-dimensional band-structure engineering. Considerable effort is being devoted to the investigation of effects due to the exciton-phonon interaction on the optical properties of quantum dots. Our theory of photoluminescence and Raman scattering in

J. T. Devreese

2002-01-01

207

Quantum effects in nanoscale Josephson junction circuits

of the electromagnetic environment surrounding the junction has to be larger than the quantum resistance (RQ = h/4e2 6 of the electromagnetic environment. By applying a magnetic field perpendicular to the SQUID loops, the Josephson energy.45 k). In this work the high impedance environment is obtained by biasing the sample un- der test

Haviland, David

208

Polymer quantum effects on compact stars models

In this work we study a completely degenerated fermion gas at zero temperature within a semiclassical approximation for the Hamiltonian arising in polymer quantum mechanics. Polymer quantum systems are quantum mechanical models quantized in a similar way as in loop quantum gravity that allow the study of the discreteness of space and other features of the loop quantization in a simplified way. We obtain the polymer modified thermodynamical properties noticing that the corresponding Fermi energy is exactly the same as if one directly polymerizes the momentum $p_F$. We also obtain the corresponding expansion of thermodynamical variables for small values of the polymer length scale $\\lambda$. With this results we study a simple model of a compact object where the gravitational collapse is supported by electron degeneracy pressure. We find polymer corrections to the mass of the star. When compared with typical measurements of the mass of white dwarfs we obtain a bound on the polymer length of $\\lambda^2\\lesssim 10^{-26}m^2$.

Guillermo Chacon-Acosta; Hector Hernandez-Hernandez

2014-08-05

209

A Proton Recoil Telescope for Neutron Spectroscopy

NASA Astrophysics Data System (ADS)

The N2P research program funded by the INFN committee for Experimental Nuclear Physics (CSNIII) has among his goals the construction of a Proton Recoil Telescope (PRT), a detector to measure neutron energy spectra. The interest in such a detector is primarily related to the SPES project for rare beams production at the Laboratori Nazionali di Legnaro. For the SPES project it is, in fact, of fundamental importance to have reliable information about energy spectra and yield for neutrons produced by d or p projectiles on thick light targets to model the ''conversion target'' in which the p or d are converted in neutrons. These neutrons, in a second stage, will induce the Uranium fission in the ''production target''. The fission products are subsequently extracted, selected and re-accelerated to produce the exotic beam. The neutron spectra and angular distribution are important parameters to define the final production of fission fragments. In addition, this detector can be used to measure neutron spectra in the field of cancer therapy (this topic is nowadays of particular interest to INFN, for the National Centre for Hadron therapy (CNAO) in Pavia) and space applications.

Cinausero, M.; Barbui, M.; Prete, G.; Rizzi, V.; Andrighetto, A.; Pesente, S.; Fabris, D.; Lunardon, M.; Nebbia, G.; Viesti, G.; Moretto, S.; Morando, M.; Zenoni, A.; Bocci, F.; Donzella, A.; Bonomi, G.; Fontana, A.

2006-05-01

210

Effective field theory of relativistic quantum hall systems

NASA Astrophysics Data System (ADS)

Motivated by the observation of the fractional quantum Hall effect in graphene, we consider the effective field theory of relativistic quantum Hall states. We find that, beside the Chern-Simons term, the effective action also contains a term of topological nature, which couples the electromagnetic field with a topologically conserved current of 2 + 1 dimensional relativistic fluid. In contrast to the Chern-Simons term, the new term involves the spacetime metric in a nontrivial way. We extract the predictions of the effective theory for linear electromagnetic and gravitational responses. For fractional quantum Hall states at the zeroth Landau level, additional holomorphic constraints allow one to express the results in terms of two dimensionless constants of topological nature.

Golkar, Siavash; Roberts, Matthew M.; Son, Dam Thanh

2014-12-01

211

Effective Field Theory of Relativistic Quantum Hall Systems

Motivated by the observation of the fractional quantum Hall effect in graphene, we consider the effective field theory of relativistic quantum Hall states. We find that, beside the Chern-Simons term, the effective action also contains a term of topological nature, which couples the electromagnetic field with a topologically conserved current of $2+1$ dimensional relativistic fluid. In contrast to the Chern-Simons term, the new term involves the spacetime metric in a nontrivial way. We extract the predictions of the effective theory for linear electromagnetic and gravitational responses. For fractional quantum Hall states at the zeroth Landau level, additional holomorphic constraints allow one to express the results in terms of two dimensionless constants of topological nature.

Siavash Golkar; Matthew M. Roberts; Dam Thanh Son

2014-03-17

212

Effective Field Theory of Relativistic Quantum Hall Systems

Motivated by the observation of the fractional quantum Hall effect in graphene, we consider the effective field theory of relativistic quantum Hall states. We find that, beside the Chern-Simons term, the effective action also contains a term of topological nature, which couples the electromagnetic field with a topologically conserved current of $2+1$ dimensional relativistic fluid. In contrast to the Chern-Simons term, the new term involves the spacetime metric in a nontrivial way. We extract the predictions of the effective theory for linear electromagnetic and gravitational responses. For fractional quantum Hall states at the zeroth Landau level, additional holomorphic constraints allow one to express the results in terms of two dimensionless constants of topological nature.

Golkar, Siavash; Son, Dam Thanh

2014-01-01

213

Quantum Stress Tensor Fluctuation Effects in Inflationary Cosmology

We review several related investigations of the effects of the quantum stress tensor of a conformal field in inflationary cosmology. Particular attention will be paid to the effects of quantum stress tensor fluctuations as a source of density and tensor perturbations in inflationary models. These effects can possibly depend upon the total expansion factor during inflation, and hence be much larger than one might otherwise expect. They have the potential to contribute a non-scale invariant and non-Gaussian component to the primordial spectrum of perturbations, and might be observable.

Jen-Tsung Hsiang; Chun-Hsien Wu; L. H. Ford; Kin-Wang Ng

2011-08-22

214

, a scattering phase shift at the Kondo resonance in a quantum dot has been measured using a twoKondo effect of quantum dots in the quantum Hall regime Mahn-Soo Choi, N. Y. Hwang, and S.-R. Eric effect of quantum dots involving the precursor of the Landau-level filling factor 1 state in the quantum

Choi, Mahn-Soo

215

NASA Astrophysics Data System (ADS)

We present in detail an alternative experimental set-up and data analysis, based on the electron-recoil ion and recoil ion-projectile coincidence techniques, that enable the measurement of partial pure ionization and partial charge exchange cross sections for an effusive gas jet set-up, where the absolute target density and recoil ion efficiency cannot be measured directly. The method is applied to the ionization of helium atoms due to collision with partially stripped C3 + projectiles. In order to check the method, the results are compared to data available in the literature where the target density and recoil ion detection efficiency were measured directly. The pure ionization channel is compared to the electron capture channel.

Wolff, W.; de Souza, Ihani J.; Tavares, André C.; de Oliveira, G. F. S.; Luna, H.

2012-12-01

216

``Interaction--free'' interaction: entangling evolution via quantum Zeno effect

The effect of entangling evolution induced by frequently repeated quantum measurement is presented. The interesting possibility of conditional freezing the system in maximally entangled state out of Zeno effect regime is also revealed. The illustration of the phenomena in terms of dynamical version of ``interaction free'' measurement is presented. Some general conclusions are provided.

Pawe? Horodecki

1998-07-11

217

Ratchet effects in graphene and quantum wells with lateral superlattice

Theoretical and experimental studies on the ratchet effects in graphene and in quantum wells with a lateral superlattice excited by alternating electric fields of terahertz frequency range are presented. We discuss the Seebeck ratchet effect and helicity driven photocurrents and show that the photocurrent generation is based on the combined action of a spatially periodic in-plane potential and a spatially modulated light.

Golub, L. E.; Nalitov, A. V.; Ivchenko, E. L. [Ioffe Physical-Technical Institute of the Russian Academy of Sciences, St. Petersburg (Russian Federation); Olbrich, P.; Kamann, J.; Eroms, J.; Weiss, D.; Ganichev, S. D. [Terahertz Center, University of Regensburg, Regensburg (Germany)

2013-12-04

218

Non-Resonant Effects in Implementation of Quantum Shor Algorithm

We simulate Shor's algorithm on an Ising spin quantum computer. The influence of non-resonant effects is analyzed in detail. It is shown that our ``$2\\pi k$''-method successfully suppresses non-resonant effects even for relatively large values of the Rabi frequency.

G. P. Berman; G. D. Doolen; G. V. Lopez; V. I. Tsifrinovich

1999-09-09

219

Observation of the fractional quantum Hall effect in graphene.

When electrons are confined in two dimensions and subject to strong magnetic fields, the Coulomb interactions between them can become very strong, leading to the formation of correlated states of matter, such as the fractional quantum Hall liquid. In this strong quantum regime, electrons and magnetic flux quanta bind to form complex composite quasiparticles with fractional electronic charge; these are manifest in transport measurements of the Hall conductivity as rational fractions of the elementary conductance quantum. The experimental discovery of an anomalous integer quantum Hall effect in graphene has enabled the study of a correlated two-dimensional electronic system, in which the interacting electrons behave like massless chiral fermions. However, owing to the prevailing disorder, graphene has so far exhibited only weak signatures of correlated electron phenomena, despite intense experimental and theoretical efforts. Here we report the observation of the fractional quantum Hall effect in ultraclean, suspended graphene. In addition, we show that at low carrier density graphene becomes an insulator with a magnetic-field-tunable energy gap. These newly discovered quantum states offer the opportunity to study correlated Dirac fermions in graphene in the presence of large magnetic fields. PMID:19881489

Bolotin, Kirill I; Ghahari, Fereshte; Shulman, Michael D; Stormer, Horst L; Kim, Philip

2009-11-12

220

Colloidal quantum dot photovoltaics: the effect of polydispersity.

The size-effect tunability of colloidal quantum dots enables facile engineering of the bandgap at the time of nanoparticle synthesis. The dependence of effective bandgap on nanoparticle size also presents a challenge if the size dispersion, hence bandgap variability, is not well-controlled within a given quantum dot solid. The impact of this polydispersity is well-studied in luminescent devices as well as in unipolar electronic transport; however, the requirements on monodispersity have yet to be quantified in photovoltaics. Here we carry out a series of combined experimental and model-based studies aimed at clarifying, and quantifying, the importance of quantum dot monodispersity in photovoltaics. We successfully predict, using a simple model, the dependence of both open-circuit voltage and photoluminescence behavior on the density of small-bandgap (large-diameter) quantum dot inclusions. The model requires inclusion of trap states to explain the experimental data quantitatively. We then explore using this same experimentally tested model the implications of a broadened quantum dot population on device performance. We report that present-day colloidal quantum dot photovoltaic devices with typical inhomogeneous linewidths of 100-150 meV are dominated by surface traps, and it is for this reason that they see marginal benefit from reduction in polydispersity. Upon eliminating surface traps, achieving inhomogeneous broadening of 50 meV or less will lead to device performance that sees very little deleterious impact from polydispersity. PMID:22257205

Zhitomirsky, David; Kramer, Illan J; Labelle, André J; Fischer, Armin; Debnath, Ratan; Pan, Jun; Bakr, Osman M; Sargent, Edward H

2012-02-01

221

Entanglement switching via the Kondo effect in triple quantum dots

NASA Astrophysics Data System (ADS)

We consider a triple quantum dot system in a triangular geometry with one of the dots connected to metallic leads. Using Wilson's numerical renormalization group method, we investigate quantum entanglement and its relation to the thermodynamic and transport properties in the regime where each of the dots is singly occupied on average, but with non-negligible charge fluctuations. It is shown that even in the regime of significant charge fluctuations the formation of the Kondo singlets induces switching between separable and perfectly entangled states. The quantum phase transition between unentangled and entangled states is analyzed quantitatively and the corresponding phase diagram is explained by exactly solvable spin model. In the framework of an effective model we also explain smearing of the entanglement transition for cases when the symmetry of the triple quantum dot system is relaxed.

Tooski, S. B.; Bu?ka, Bogdan R.; Žitko, Rok; Ramšak, Anton

2014-06-01

222

Coulomb effects in semiconductor quantum dots

Coulomb correlations in the optical spectra of semiconductor quantum dots are investigated using a full-diagonalization approach. The resulting multi-exciton spectra are discussed in terms of the symmetry of the involved states. Characteristic features of the spectra like the nearly equidistantly spaced s-shell emission lines and the approximately constant p-shell transition energies are explained using simplified Hamiltonians that are derived taking

Norman Baer; Paul Gartner; Frank Jahnke

2004-01-01

223

Quantum electrodynamical effects in dusty plasmas

A new nonlinear electromagnetic wave mode in a magnetized dusty plasma is predicted. Its existence depends on the interaction of an intense circularly polarized electromagnetic wave with a dusty plasma, where quantum electrodynamical photon-photon scattering is taken into account. Specifically, we consider a dusty electron-positron-ion plasma and show that the propagation of the new mode is admitted. It could be

M. Marklund; L. Stenflo; P. K. Shukla; G. Brodin

2005-01-01

224

Quantum electrodynamical effects in dusty plasmas

A new nonlinear electromagnetic wave mode in a magnetized dusty plasma is predicted. Its existence depends on the interaction of an intense circularly polarized electromagnetic wave with a dusty plasma, where quantum electrodynamical photon-photon scattering is taken into account. Specifically, we consider a dusty electron-positron-ion plasma and show that the propagation of the new mode is admitted. It could be of significance for the physics of supernova remnants and in neutron star formation.

Marklund, M.; Stenflo, L.; Shukla, P.K.; Brodin, G. [Department of Physics, Umeaa University, SE-901 87 Umeaa Sweden and Centre for Fundamental Physics, Rutherford Appleton Laboratory, Chilton Didcot, Oxfordshire OX11 0QX (United Kingdom); Department of Physics, Umeaa University, SE-901 87 Umeaa (Sweden); Department of Physics, Umeaa University, SE-901 87 Umeaa (Sweden) and Centre for Fundamental Physics, Rutherford Appleton Laboratory, Chilton Didcot, Oxfordshire OX11 0QX (United Kingdom)

2005-07-15

225

Quantum Electrodynamical Effects in Dusty Plasmas

A new nonlinear electromagnetic wave mode in a magnetized dusty plasma is predicted. Its existence depends on the interaction of an intense circularly polarized electromagnetic wave with a dusty plasma, where quantum electrodynamical photon-photon scattering is taken into account. Specifically, we consider a dusty electron-positron-ion plasma, and show that the propagation of the new mode is admitted. It could be of significance for the physics of supernova remnants and in neutron star formation.

M. Marklund; L. Stenflo; P. K. Shukla; G. Brodin

2005-03-17

226

Stark Effect of Interactive Electron-hole pairs in Spherical Semiconductor Quantum Dots

Stark Effect of Interactive Electron-hole pairs in Spherical Semiconductor Quantum Dots B. Billaud1, on the quantum-confinement Stark effects for spherical semiconducting quantum dots in the regime of strong are found to be in good agreement with experimental data over a significant domain of quantum dot sizes

227

A Predictive Theory for Elastic Scattering and Recoil of Protons from $^4$He

Low-energy cross sections for elastic scattering and recoil of protons from $^4$He nuclei (also known as $\\alpha$ particles) are calculated directly by solving the Schr\\"odinger equation for five nucleons interacting through accurate two- and three-nucleon forces derived within the framework of chiral effective field theory. Precise knowledge of these processes at various proton backscattering/recoil angles and energies is needed for the ion-beam analysis of numerous materials, from the surface layers of solids, to thin films, to fusion-reactor materials. Indeed, the same elastic scattering process, in two different kinematic configurations, can be used to probe concentrations and depth profiles of either hydrogen or helium. We compare our results to available experimental data and show that direct calculations with modern nuclear potentials can help to resolve remaining inconsistencies among different data sets and can be used to predict these cross sections when measurements are not available.

Guillaume Hupin; Sofia Quaglioni; Petr Navrátil

2014-09-02

228

Predictive theory for elastic scattering and recoil of protons from 4He

NASA Astrophysics Data System (ADS)

Low-energy cross sections for elastic scattering and recoil of protons from 4He nuclei (also known as ? particles) are calculated directly by solving the Schrödinger equation for five nucleons interacting through accurate two- and three-nucleon forces derived within the framework of chiral effective field theory. Precise knowledge of these processes at various proton backscattering/recoil angles and energies is needed for the ion-beam analysis of numerous materials, from the surface layers of solids, to thin films, to fusion-reactor materials. Indeed, the same elastic scattering process, in two different kinematic configurations, can be used to probe the concentrations and depth profiles of either hydrogen or helium. We compare our results to available experimental data and show that direct calculations with modern nuclear potentials can help to resolve remaining inconsistencies among data sets and can be used to predict these cross sections when measurements are not available.

Hupin, Guillaume; Quaglioni, Sofia; Navrátil, Petr

2014-12-01

229

A coherent understanding of low-energy nuclear recoils in liquid xenon

Liquid xenon detectors such as XENON10 and XENON100 obtain a significant fraction of their sensitivity to light (?<10 GeV) particle dark matter by looking for nuclear recoils of only a few keV, just above the detector threshold. Yet in this energy regime a correct treatment of the detector threshold and resolution remains unclear. The energy dependence of the scintillation yield of liquid xenon for nuclear recoils also bears heavily on detector sensitivity, yet numerous measurements have not succeeded in obtaining concordant results. In this article we show that the ratio of detected ionization to scintillation can be leveraged to constrain the scintillation yield. We also present a rigorous treatment of liquid xenon detector threshold and energy resolution. Notably, the effective energy resolution differs significantly from a simple Poisson distribution. We conclude with a calculation of dark matter exclusion limits, and show that existing data from liquid xenon detectors strongly constrain recent interpretations of light dark matter.

Sorensen, Peter, E-mail: pfs@llnl.gov [Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, CA 94550 (United States)

2010-09-01

230

Quantum Zeno effect for a free-moving particle

NASA Astrophysics Data System (ADS)

Although the quantum Zeno effect takes its name from Zeno's arrow paradox, the effect of frequently observing the position of a freely moving particle on its motion has not been analyzed in detail in the frame of standard quantum mechanics. We study the evolution of a moving free particle while monitoring whether it lingers in a given region of space, and explain the dependence of the lingering probability on the frequency of the measurements and the initial momentum of the particle. Stopping the particle entails the emergence of Schrödinger cat states during the observed evolution, closely connected to the high-order diffraction modes in Fabry-Pérot optical resonators.

Porras, Miguel A.; Luis, Alfredo; Gonzalo, Isabel

2014-12-01

231

The quantum effective mass Hamilton-Jacobi problem

NASA Astrophysics Data System (ADS)

In this paper, the quantum Hamilton-Jacobi theory based on the position-dependent mass model is studied. Two effective mass functions having different singularity structures are used to examine the Morse and Pöschl-Teller potentials. The residue method is used to obtain the solutions of the quantum effective mass- Hamilton-Jacobi equation. Further, it is shown that the eigenstates of the generalized non-Hermitian Swanson Hamiltonian for Morse and Pöschl-Teller potentials can be obtained by using the Riccati equation without solving a differential equation.

Ye?ilta?, Özlem

2010-03-01

232

Focus on quantum effects and noise in biomolecules

NASA Astrophysics Data System (ADS)

The role of quantum mechanics in biological organisms has been a fundamental question of twentieth-century biology. It is only now, however, with modern experimental techniques, that it is possible to observe quantum mechanical effects in bio-molecular complexes directly. Indeed, recent experiments have provided evidence that quantum effects such as wave-like motion of excitonic energy flow, delocalization and entanglement can be seen even in complex and noisy biological environments (Engel et al 2007 Nature 446 782; Collini et al 2010 Nature 463 644; Panitchayangkoon et al 2010 Proc. Natl Acad. Sci. USA 107 12766). Motivated by these observations, theoretical work has highlighted the importance of an interplay between environmental noise and quantum coherence in such systems (Mohseni et al 2008 J. Chem. Phys. 129 174106; Plenio and Huelga 2008 New J. Phys. 10 113019; Olaya-Castro et al 2008 Phys. Rev. B 78 085115; Rebentrost et al 2009 New J. Phys. 11 033003; Caruso et al 2009 J. Chem. Phys. 131 105106; Ishizaki and Fleming 2009 J. Chem. Phys. 130 234111). All of this has led to a surge of interest in the exploration of quantum effects in biological systems in order to understand the possible relevance of non-trivial quantum features and to establish a potential link between quantum coherence and biological function. These studies include not only exciton transfer across light harvesting complexes, but also the avian compass (Ritz et al 2000 Biophys. J. 78 707), and the olfactory system (Turin 1996 Chem. Sens. 21 773; Chin et al 2010 New J. Phys. 12 065002). These examples show that the full understanding of the dynamics at bio-molecular length (10 Å) and timescales (sub picosecond) in noisy biological systems can uncover novel phenomena and concepts and hence present a fertile ground for truly multidisciplinary research.

Fleming, G. R.; Huelga, S. F.; Plenio, M. B.

2011-11-01

233

The spin Hall effect in a quantum gas.

Electronic properties such as current flow are generally independent of the electron's spin angular momentum, an internal degree of freedom possessed by quantum particles. The spin Hall effect, first proposed 40 years ago, is an unusual class of phenomena in which flowing particles experience orthogonally directed, spin-dependent forces--analogous to the conventional Lorentz force that gives the Hall effect, but opposite in sign for two spin states. Spin Hall effects have been observed for electrons flowing in spin-orbit-coupled materials such as GaAs and InGaAs (refs 2, 3) and for laser light traversing dielectric junctions. Here we observe the spin Hall effect in a quantum-degenerate Bose gas, and use the resulting spin-dependent Lorentz forces to realize a cold-atom spin transistor. By engineering a spatially inhomogeneous spin-orbit coupling field for our quantum gas, we explicitly introduce and measure the requisite spin-dependent Lorentz forces, finding them to be in excellent agreement with our calculations. This 'atomtronic' transistor behaves as a type of velocity-insensitive adiabatic spin selector, with potential application in devices such as magnetic or inertial sensors. In addition, such techniques for creating and measuring the spin Hall effect are clear prerequisites for engineering topological insulators and detecting their associated quantized spin Hall effects in quantum gases. As implemented, our system realizes a laser-actuated analogue to the archetypal semiconductor spintronic device, the Datta-Das spin transistor. PMID:23739329

Beeler, M C; Williams, R A; Jiménez-García, K; LeBlanc, L J; Perry, A R; Spielman, I B

2013-06-13

234

Dynamical quantum Hall effect in the parameter space

Geometric phases in quantum mechanics play an extraordinary role in broadening our understanding of fundamental significance of geometry in nature. One of the best known examples is the Berry phase [M.V. Berry (1984), Proc. Royal. Soc. London A, 392:45], which naturally emerges in quantum adiabatic evolution. So far the applicability and measurements of the Berry phase were mostly limited to systems of weakly interacting quasi-particles, where interference experiments are feasible. Here we show how one can go beyond this limitation and observe the Berry curvature, and hence the Berry phase, in generic systems as a nonadiabatic response of physical observables to the rate of change of an external parameter. These results can be interpreted as a dynamical quantum Hall effect in a parameter space. The conventional quantum Hall effect is a particular example of the general relation if one views the electric field as a rate of change of the vector potential. We illustrate our findings by analyzing the response of interacting spin chains to a rotating magnetic field. We observe the quantization of this response, which we term the rotational quantum Hall effect. PMID:22493228

Gritsev, V.; Polkovnikov, A.

2012-01-01

235

Quantum effects in unimolecular reaction dynamics

This work is primarily concerned with the development of models for the quantum dynamics of unimolecular isomerization and photodissociation reactions. We apply the rigorous quantum methodology of a Discrete Variable Representation (DVR) with Absorbing Boundary Conditions (ABC) to these models in an attempt to explain some very surprising results from a series of experiments on vibrationally excited ketene. Within the framework of these models, we are able to identify the experimental signatures of tunneling and dynamical resonances in the energy dependence of the rate of ketene isomerization. Additionally, we investigate the step-like features in the energy dependence of the rate of dissociation of triplet ketene to form {sup 3}B{sub 1} CH{sub 2} + {sup 1}{sigma}{sup +} CO that have been observed experimentally. These calculations provide a link between ab initio calculations of the potential energy surfaces and the experimentally observed dynamics on these surfaces. Additionally, we develop an approximate model for the partitioning of energy in the products of photodissociation reactions of large molecules with appreciable barriers to recombination. In simple bond cleavage reactions like CH{sub 3}COCl {yields} CH{sub 3}CO + Cl, the model does considerably better than other impulsive and statistical models in predicting the energy distribution in the products. We also investigate ways of correcting classical mechanics to include the important quantum mechanical aspects of zero-point energy. The method we investigate is found to introduce a number of undesirable dynamical artifacts including a reduction in the above-threshold rates for simple reactions, and a strong mixing of the chaotic and regular energy domains for some model problems. We conclude by discussing some of the directions for future research in the field of theoretical chemical dynamics.

Gezelter, J.D.

1995-12-01

236

Band-edge electroabsorption in quantum well structures - The quantum-confined Stark effect

NASA Astrophysics Data System (ADS)

Theory and extended experimental results are presented for the large shift in optical absorption in GaAs-AlGaAs quantum-well structures with electric field perpendicular to the layers. In contrast to the Stark effect on atoms or on excitons in bulk semiconductors, the exciton resonances remain resolved even for shifts much larger than the zero-field binding energy and fields more than 50 times the classical ionization field. The model explains these results as a consequence of the quantum confinement of carriers.

Miller, D. A. B.; Chemla, D. S.; Damen, T. C.; Wood, T. H.; Burrus, C. A.; Gossard, A. C.; Wiegmann, W.

1984-11-01

237

Finite-size effects in the quantum anomalous Hall system

NASA Astrophysics Data System (ADS)

We theoretically investigate the finite size effect in quantum anomalous Hall (QAH) system. Using Mn-doped HgTe quantum well as an example, we demonstrate that the coupling between the edge states is spin dependent and is related not only to the distance between the edges but also to the doping concentration. Thus with proper tuning of the two, we can get four kinds of transport regimes: quantum spin Hall, QAH, edge conducting, and normal insulator. These transport regimes have distinguishing edge conducting properties while the bulk is insulting. Our results give a general picture of the finite size effect in a QAH system, and are important for the transport experiments in QAH nanomaterials as well as future device applications.

Fu, Hua-Hua; Lü, Jing-Tao; Gao, Jin-Hua

2014-05-01

238

Modeling quantum gravity effects in inflation

NASA Astrophysics Data System (ADS)

Cosmological models in 1+1 dimensions are an ideal setting for investigating the quantum structure of inflationary dynamics — gravity is renormalizable, while there is room for spatial structure not present in the minisuperspace approximation. We use this fortuitous convergence to investigate the mechanism of slow-roll eternal inflation. A variant of 1+1 Liouville gravity coupled to matter is shown to model precisely the scalar sector of cosmological perturbations in 3+1 dimensions. A particular example of quintessence in 1+1d is argued on the one hand to exhibit slow-roll eternal inflation according to standard criteria; on the other hand, a field redefinition relates the model to pure de Sitter gravity coupled to a free scalar matter field with no potential. This and other examples show that the standard logic leading to slow-roll eternal inflation is not invariant under field redefinitions, thus raising concerns regarding its validity. Aspects of the quantization of Liouville gravity as a model of quantum de Sitter space are also discussed.

Martinec, Emil J.; Moore, Wynton E.

2014-07-01

239

Advanced theory of multiple exciton generation effect in quantum dots

NASA Astrophysics Data System (ADS)

The theoretical aspects of the effect of multiple exciton generation (MEG) in quantum dots (QDs) have been analysed in this work. The statistical theory of MEG in QDs based on Fermi's approach is presented, taking into account the momentum conservation law. According to Fermi this approach should give the ultimate quantum efficiencies of multiple particle generation. The microscopic mechanism of this effect is based on the theory of electronic "shaking". According to this approach, the wave function of "shaking" electrons can be selected as Plato's functions with effective charges depending on the number of generated excitons. From the theory it is known increasing the number of excitons leads to enhancement of the Auger recombination of electrons which results in reduced quantum yields of excitons. The deviation of the averaged multiplicity of the MEG effect from the Poisson law of fluctuations has been investigated on the basis of synergetics approaches. In addition the role of interface electronic states of QDs and ligands has been considered by means of quantum mechanical approaches. The size optimisation of QDs has been performed to maximise the multiplicity of the MEG effect.

Oksengendler, B. L.; Turaeva, N. N.; Rashidova, S. S.

2012-06-01

240

In the framework of the one boson exchange model, we have calculated the effective potentials between two heavy mesons $B \\bar{B}^{*}$ and $D \\bar{D}^{*}$ from the t- and u-channel $\\pi$, $\\eta$, $\\rho$, $\\omega$ and $\\sigma$ meson exchange with four kinds of quantum number: $I=0$, $J^{PC}=1^{++}$; $I=0$, $J^{PC}=1^{+-}$; $I=1$, $J^{PC}=1^{++}$; $I=1$, $J^{PC}=1^{+-}$. We keep the recoil corrections to the $B \\bar{B}^{*}$ and $D \\bar{D}^{*}$ system up to $O(\\frac{1}{M^2})$. The spin orbit force appears at $O(\\frac{1}{M})$, which turns out to be important for the very loosely bound molecular states. Our numerical results show that the momentum-related corrections are unfavorable to the formation of the molecular states in the $I=0$, $J^{PC}=1^{++}$ and $I=1$, $J^{PC}=1^{+-}$ channels in the $D \\bar{D}^{*}$ systems.

Lu Zhao; Li Ma; Shi-Lin Zhu

2014-03-19

241

Quantum Zeno and anti-Zeno effects on quantum and classical correlations

In this paper we study the possibility of modifying the dynamics of both quantum correlations, such as entanglement and discord, and classical correlations of an open bipartite system by means of the quantum Zeno effect. We consider two qubits coupled to a common boson reservoir at zero temperature. This model describes, for example, two atoms interacting with a quantized mode of a lossy cavity. We show that when the frequencies of the two atoms are symmetrically detuned from that of the cavity mode, oscillations between the Zeno and anti-Zeno regimes occur. We also calculate analytically the time evolution of both classical correlations and quantum discord, and we compare the Zeno dynamics of entanglement with the Zeno dynamics of classical correlations and discord.

Francica, F.; Plastina, F. [Dipartimento di Fisica, Universita della Calabria, I-87036 Arcavacata di Rende (Italy); INFN-Gruppo Collegato di Cosenza, Cosenza (Italy); Maniscalco, S. [Turku Centre for Quantum Physics, Department of Physics and Astronomy, University of Turku, FIN-20014 Turun yliopisto (Finland)

2010-11-15

242

Effects of quantum coherence in metalloprotein electron transfer

NASA Astrophysics Data System (ADS)

Many intramolecular electron transfer (ET) reactions in biology are mediated by metal centers in proteins. This process is commonly described by a model of diffusive hopping according to the semiclassical theories of Marcus and Hopfield. However, recent studies have raised the possibility that nontrivial quantum mechanical effects play a functioning role in certain biomolecular processes. Here, we investigate the potential effects of quantum coherence in biological ET by extending the semiclassical model to allow for the possibility of quantum coherent phenomena using a quantum master equation based on the Holstein Hamiltonian. We test the model on the structurally defined chain of seven iron-sulfur clusters in nicotinamide adenine dinucleotide plus hydrogen:ubiquinone oxidoreductase (complex I), a crucial respiratory enzyme and one of the longest chains of metal centers in biology. Using experimental parameters where possible, we find that, in limited circumstances, a small quantum mechanical contribution can provide a marked increase in the ET rate above the semiclassical diffusive-hopping rate. Under typical biological conditions, our model reduces to well-known diffusive behavior.

Dorner, Ross; Goold, John; Heaney, Libby; Farrow, Tristan; Vedral, Vlatko

2012-09-01

243

Energetic recoils in UO2 simulated using five different potentials.

This report presents the results of classical molecular dynamics simulations of the diffuse premelting transition, melting, and defect production by 1 keV U recoils in UO(2) using five different rigid ion potentials. The experimentally observed premelting transition occurred for all five cases. For all the potentials studied, dynamic defect annealing is highly effective and is accompanied by replacement events on the anion sublattice. The primary damage state after approximately 15 ps consists of isolated Frenkel pairs and interstitial and vacancy clusters of various sizes. The average displacement energy varies from approximately 28 to approximately 83 eV and the number of Frenkel pairs is different by a factor of 3 depending on the choice of potential. The size and spatial distribution of vacancy and interstitial clusters is drastically different for the potentials studied. The results provide statistics of defect production. They point to a pressing need to determine defect formation, migration, and binding energies in UO(2) from first principles and to develop reliable potentials based on this data for simulating microstructural evolution in nuclear fuel under operating conditions. PMID:19425785

Devanathan, Ram; Yu, Jianguo; Weber, William J

2009-05-01

244

Calculation of recoil implantation profiles using known range statistics

NASA Technical Reports Server (NTRS)

A method has been developed to calculate the depth distribution of recoil atoms that result from ion implantation onto a substrate covered with a thin surface layer. The calculation includes first order recoils considering projected range straggles, and lateral straggles of recoils but neglecting lateral straggles of projectiles. Projectile range distributions at intermediate energies in the surface layer are deduced from look-up tables of known range statistics. A great saving of computing time and human effort is thus attained in comparison with existing procedures. The method is used to calculate recoil profiles of oxygen from implantation of arsenic through SiO2 and of nitrogen from implantation of phosphorus through Si3N4 films on silicon. The calculated recoil profiles are in good agreement with results obtained by other investigators using the Boltzmann transport equation and they also compare very well with available experimental results in the literature. The deviation between calculated and experimental results is discussed in relation to lateral straggles. From this discussion, a range of surface layer thickness for which the method applies is recommended.

Fung, C. D.; Avila, R. E.

1985-01-01

245

NASA Astrophysics Data System (ADS)

The last years have witnessed fast growing developments in the use of quantum mechanics in technology-oriented and information-related fields, especially in metrology, in the developments of nano-devices and in understanding highly efficient transport processes. The consequent theoretical and experimental outcomes are now driving new experimental tests of quantum mechanical effects with unprecedented accuracies that carry with themselves the concrete possibility of novel technological spin-offs. Indeed, the manifold advances in quantum optics, atom and ion manipulations, spintronics and nano-technologies are allowing direct experimental verifications of new ideas and their applications to a large variety of fields. All of these activities have revitalized interest in quantum mechanics and created a unique framework in which theoretical and experimental physics have become fruitfully tangled with information theory, computer, material and life sciences. This special issue aims to provide an overview of what is currently being pursued in the field and of what kind of theoretical reference frame is being developed together with the experimental and theoretical results. It consists of three sections: 1. Memory effects in quantum dynamics and quantum channels 2. Driven open quantum systems 3. Experiments concerning quantum coherence and/or decoherence The first two sections are theoretical and concerned with open quantum systems. In all of the above mentioned topics, the presence of an external environment needs to be taken into account, possibly in the presence of external controls and/or forcing, leading to driven open quantum systems. The open system paradigm has proven to be central in the analysis and understanding of many basic issues of quantum mechanics, such as the measurement problem, quantum communication and coherence, as well as for an ever growing number of applications. The theory is, however, well-settled only when the so-called Markovian or memoryless, approximation applies. When strong coupling or long environmental relaxation times make memory effects important for a realistic description of the dynamics, new strategies are asked for and the assessment of the general structure of non-Markovian dynamical equations for realistic systems is a crucial issue. The impact of quantum phenomena such as coherence and entanglement in biology has recently started to be considered as a possible source of the high efficiency of certain biological mechanisms, including e.g. light harvesting in photosynthesis and enzyme catalysis. In this effort, the relatively unknown territory of driven open quantum systems is being explored from various directions, with special attention to the creation and stability of coherent structures away from thermal equilibrium. These investigations are likely to advance our understanding of the scope and role of quantum mechanics in living systems; at the same time they provide new ideas for the developments of next generations of devices implementing highly efficient energy harvesting and conversion. The third section concerns experimental studies that are currently being pursued. Multidimensional nonlinear spectroscopy, in particular, has played an important role in enabling experimental detection of the signatures of coherence. Recent remarkable results suggest that coherence—both electronic and vibrational—survive for substantial timescales even in complex biological systems. The papers reported in this issue describe work at the forefront of this field, where researchers are seeking a detailed understanding of the experimental signatures of coherence and its implications for light-induced processes in biology and chemistry.

Benatti, Fabio; Floreanini, Roberto; Scholes, Greg

2012-08-01

246

is the use of classical molecular dynamics simulations with molecular mechanical forcefields.7Hybrid approach for including electronic and nuclear quantum effects in molecular dynamics profiles. The dynamical effects are studied with the molecular dynamics with quantum transitions MDQT

Hammes-Schiffer, Sharon

247

Magnetic effects in curved quantum waveguides D. Krejcirik

Magnetic effects in curved quantum waveguides D. KrejcirÂ´ik and N. Raymond March 26, 2013 Abstract The interplay among the spectrum, geometry and magnetic field in tubular neigh- bourhoods of curves in Euclidean convergence, we derive effec- tive, lower-dimensional models which depend on the intensity of the magnetic

Boyer, Edmond

248

Biexciton effects in femtosecond nonlinear transmission of semiconductor quantum dots

The dynamics of carrier-induced absorption changes in CdSe quantum dots are investigated with femtosecond spectroscopy. After excitation with 4-eV photons a redshift of the lowest optical transition is observed in the initial phase of carrier relaxation. This shift is attributed to a biexciton effect where two electron-hole pairs interact via the Coulomb potential.

V. Klimov; S. Hunsche; H. Kurz

1994-01-01

249

The effect of quantum nuclear motion on hydrogen bonding

The effect of quantum nuclear motion on hydrogen bonding Ross McKenzie University of Queensland zero motion and tunnelling do not exceptions are molecules involving hydrogen bonding, including water experiments where deuterium. I will introduce a simple model for hydrogen bonding [1] based on a two space

Shyamasundar, R.K.

250

Effect of Quantum Fluctuation on the Andreev Reflection

NASA Astrophysics Data System (ADS)

We investigate the dynamical quantum fluctuation effect on an Andreev current through an ultrasmall superconductor in the Coulomb blockade regime. We calculate the current using a phenomenological gauge invariant model and the real-time path-integral method. We choose a special gauge which absorbs the scalar potential to convert the phase of a superconductor as a dynamical variable. A zero-energy phase fluctuation of the superconductor suppresses the Andreev current at low bias voltage. This suppression is expected to be observed in samples with large level spacing and small charging energy which allow the coexistence of a large quantum fluctuation and Andreev reflection process.

Utsumi, Yasuhiro; Hayashi, Masahiko; Ebisawa, Hiromichi

2000-09-01

251

Effects of quantum noise in a dye-laser model

NASA Astrophysics Data System (ADS)

The steady-state properties of a dye laser model with white quantum noise and strongly colored pump noise are investigated. An effective diffusion coefficient in the steady state is presented. Our coefficient differs from that of Fox and Roy [Phys. Rev. A 35, 1838 (1987)]. We compare our results with the measurements and simulations of Lett, Short, and Mandel [Phys. Rev. Lett. 52, 341 (1984)], and the results of Fox and Roy, respectively. We find that the quantum noise plays an important role in the steady-state analysis of laser fluctuations below and near threshold.

Jia, Ya; Li, Jia-Rong

1997-03-01

252

Tunneling in Polymer Quantization and the Quantum Zeno Effect

As an application of the polymer quantization scheme, in this work we investigate the one dimensional quantum mechanical tunneling phenomenon from the perspective of polymer representation of a non-relativistic point particle and derive the transmission and reflection coefficients. Since any tunneling phenomenon inevitably evokes a tunneling time we attempt an analytical calculation of tunneling times by defining an operator well suited in discrete spatial geometry. The results that we come up with hint at appearance of the Quantum Zeno Effect in polymer framework.

Durmus Ali Demir; Ozan Sargin

2014-09-25

253

The Quantum Spin Hall Effect: Theory and Experiment

The search for topologically non-trivial states of matter has become an important goal for condensed matter physics. Recently, a new class of topological insulators has been proposed. These topological insulators have an insulating gap in the bulk, but have topologically protected edge states due to the time reversal symmetry. In two dimensions the helical edge states give rise to the quantum spin Hall (QSH) effect, in the absence of any external magnetic field. Here we review a recent theory which predicts that the QSH state can be realized in HgTe/CdTe semiconductor quantum wells. By varying the thickness of the quantum well, the band structure changes from a normal to an 'inverted' type at a critical thickness d{sub c}. We present an analytical solution of the helical edge states and explicitly demonstrate their topological stability. We also review the recent experimental observation of the QSH state in HgTe/(Hg,Cd)Te quantum wells. We review both the fabrication of the sample and the experimental setup. For thin quantum wells with well width d{sub QW} < 6.3 nm, the insulating regime shows the conventional behavior of vanishingly small conductance at low temperature. However, for thicker quantum wells (d{sub QW} > 6.3 nm), the nominally insulating regime shows a plateau of residual conductance close to 2e{sup 2}/h. The residual conductance is independent of the sample width, indicating that it is caused by edge states. Furthermore, the residual conductance is destroyed by a small external magnetic field. The quantum phase transition at the critical thickness, d{sub c} = 6.3 nm, is also independently determined from the occurrence of a magnetic field induced insulator to metal transition.

Konig, Markus; Buhmann, Hartmut; Molenkamp, Laurens W.; /Wurzburg U.; Hughes, Taylor L.; /Stanford U., Phys. Dept.; Liu, Chao-Xing; /Tsinghua U., Beijing /Stanford U., Phys. Dept.; Qi, Xiao-Liang; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

2010-03-19

254

Time-of-flight scattering and recoiling spectrometry

Ion scattering and recoiling spectrometry consists of directing a collimated beam of monoenergetic ions towards a surface and measuring the flux of scattered and recoiled particles from this surface. When the neutral plus ion flux is velocity selected by measuring the flight times from the sample to the detector, the technique is called time-of-flight scattering and recoiling spectrometry (TOF-SARS). TOF-SARS is capable of (1) surface elemental analysis by applying classical mechanics to the velocities of the particles, (2) surface structural analysis by monitoring the angular anisotropies in the particle flux, and (3) ion-surface electron exchange probabilities by analysis of the ion/neutral fractions in the particle flux. Examples of these three areas are presented herein.

Rabalais, J.W. (Department of Chemistry, University of Houston, Houston, Texas 77204-5641 (US))

1991-05-01

255

Quantum effects in high-gain free-electron lasers.

A many-particle fully quantized theory for a free-electron laser which is valid in the high-gain regime is presented. We examine quantum corrections for the high-gain single-pass free-electron laser. It is shown that quantum effects become significant when the photon energy becomes comparable to the gain bandwidth. The initiation of the free-electron laser process from quantum fluctuations in the position and momentum of the electrons is considered, and the parameter regime for enhanced start-up is identified. Photon statistics of the free-electron laser radiation are discussed, and the photon number statistics for the self-amplified spontaneous emission are calculated. PMID:11736108

Schroeder, C B; Pellegrini, C; Chen, P

2001-11-01

256

On the Convergence in Effective Loop Quantum Cosmology

In Loop Quantum Cosmology (LQC) there is a discreteness parameter {lambda}, that has been heuristically associated to a fundamental granularity of quantum geometry. It is also possible to consider {lambda} as a regulator in the same spirit as that used in lattice field theory, where it specifies a regular lattice in the real line. A particular quantization of the k = 0 FLRW loop cosmological model yields a completely solvable model, known as solvable loop quantum cosmology(sLQC). In this contribution, we consider effective classical theories motivated by sLQC and study their {lambda}-dependence, with a special interest on the limit {lambda}{yields}0 and the role of the evolution parameter in the convergence of such limit.

Corichi, Alejandro [Instituto de Matematicas, Universidad Nacional Autonoma de Mexico, A. Postal 61-3, Morelia, Michoacan 58090 (Mexico); Center for Fundamental Theory, Institute for Gravitation and the Cosmos, Pennsylvania State University, University Park PA 16802 (United States); Vukasinac, Tatjana [Facultad de Ingenieria Civil, Universidad Michoacana de San Nicolas de Hidalgo Morelia, Michoacan 58000 (Mexico); Zapata, Jose Antonio [Instituto de Matematicas, Universidad Nacional Autonoma de Mexico, A. Postal 61-3, Morelia, Michoacan 58090 (Mexico)

2010-07-12

257

Possible observational windows for quantum effects from black holes

NASA Astrophysics Data System (ADS)

Quantum information transfer necessary to reconcile black hole evaporation with quantum mechanics, while approximately preserving regular near-horizon geometry, can be simply parametrized in terms of couplings of the black hole internal state to quantum fields of the black hole atmosphere. The necessity of transferring sufficient information for unitarization sets the strengths of these couplings. Such couplings via the stress tensor offer apparently significant advantages, and behave like quantum fluctuations of the effective metric near the horizon. At the requisite strength, these fluctuations, while soft (low energy/momentum), have significant magnitude, and so can deflect near-horizon geodesics that span distances of order the black hole radius. Thus, the presence of such couplings can result in effects that could be detected or constrained by observation: disruption of near-horizon accretion flows, scintillation of light passing close to the black hole, and alteration of gravitational wave emission from inspirals. These effects could in particular distort features of Sgr A* expected to be observed, e.g., by the Event Horizon Telescope, such as the black hole shadow and photon ring.

Giddings, Steven B.

2014-12-01

258

Quantum Hall effect in graphene decorated with disordered multilayer patches

Quantum Hall effect (QHE) is observed in graphene grown by chemical vapour deposition using platinum catalyst. The QHE is even seen in samples which are irregularly decorated with disordered multilayer graphene patches and have very low mobility (<500 cm{sup 2}V{sup ?1}s{sup ?1}). The effect does not seem to depend on electronic mobility and uniformity of the resulting material, which indicates the robustness of QHE in graphene.

Nam, Youngwoo, E-mail: youngwoo.nam@chalmers.se [Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of) [Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of); Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-412 96 Gothenburg (Sweden); Sun, Jie, E-mail: jie.sun@chalmers.se; Lindvall, Niclas; Kireev, Dmitry; Yurgens, August [Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-412 96 Gothenburg (Sweden)] [Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-412 96 Gothenburg (Sweden); Jae Yang, Seung; Rae Park, Chong [Department of Materials Science and Engineering, Seoul National University, Seoul 151-747 (Korea, Republic of)] [Department of Materials Science and Engineering, Seoul National University, Seoul 151-747 (Korea, Republic of); Woo Park, Yung [Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of)] [Department of Physics and Astronomy, Seoul National University, Seoul 151-747 (Korea, Republic of)

2013-12-02

259

Deep-submicron CMOS Single Photon Detectors and Quantum Effects

Quantum parasitic effects and miniaturization of Single Photon Avalanche Diodes in deep-submicron technologies have been studied in this thesis in detail. Tunneling noise and Random Telegraph Signal (RTS) noise have been the main two parasitic effects addressed comprehensively.\\u000aWhile the fundamental equations for tunneling count rate in SPADs have been presented, the tunneling study has been performed by comparing two

M. A. Karami

2011-01-01

260

Semiclassical droplet states in matrix quantum Hall effect

We derive semiclassical ground state solutions that correspond to the quantum Hall states earlier found in the Maxwell-Chern-Simons matrix theory. They realize the Jain composite-fermion construction and their density is piecewise constant as that of phenomenological wave functions. These results support the matrix theory as a possible effective theory of the fractional Hall effect. A crucial role is played by

Andrea Cappelli; Ivan D. Rodriguez

2008-01-01

261

A holographic model for the fractional quantum Hall effect

NASA Astrophysics Data System (ADS)

Experimental data for fractional quantum Hall systems can to a large extent be explained by assuming the existence of a ?0(2) modular symmetry group commuting with the renormalization group flow and hence mapping different phases of two-dimensional electron gases into each other. Based on this insight, we construct a phenomenological holographic model which captures many features of the fractional quantum Hall effect. Using an -invariant Einstein-Maxwell-axio-dilaton theory capturing the important modular transformation properties of quantum Hall physics, we find dyonic diatonic black hole solutions which are gapped and have a Hall conductivity equal to the filling fraction, as expected for quantum Hall states. We also provide several technical results on the general behavior of the gauge field fluctuations around these dyonic dilatonic black hole solutions: we specify a sufficient criterion for IR normalizability of the fluctuations, demonstrate the preservation of the gap under the action, and prove that the singularity of the fluctuation problem in the presence of a magnetic field is an accessory singularity. We finish with a preliminary investigation of the possible IR scaling solutions of our model and some speculations on how they could be important for the observed universality of quantum Hall transitions.

Lippert, Matthew; Meyer, René; Taliotis, Anastasios

2015-01-01

262

Quantum plasmon effects in epsilon-near-zero metamaterials

Dispersion properties of metals and propagation of quantum bulk plasmon in the high photon energy regime are studied. The nonlocal dielectric permittivity of a metal is determined by the quantum plasma effects and is calculated by applying the Wigner equation in the kinetic theory and taking into account the electron lattice collisions. The properties of epsilon near zero material are investigated in a thin gold film. The spectrum and the damping rate of the quantum bulk plasmon are obtained for a wide range of energies, and the electron wave function is analytically calculated in both classical and quantum limits. It is shown that the quantum bulk plasmons exist with a propagation length of 1 to 10nm, which strongly depends on the electron energy. The propagation length is found to be much larger than the propagation length in the classical regime which is comparable to the atomic radius and the average inter particle distance. It is found that the spatial localization of the electron wave function is extend...

Moaied, M; Ostrikov, K

2014-01-01

263

Resonant recoil in extreme mass ratio binary black hole mergers

The inspiral and merger of a binary black hole system generally leads to an asymmetric distribution of emitted radiation, and hence a recoil of the remnant black hole directed opposite to the net linear momentum radiated. The recoil velocity is generally largest for comparable mass black holes and particular spin configurations, and approaches zero in the extreme mass ratio limit. It is generally believed that for extreme mass ratios {eta}<<1, the scaling of the recoil velocity is |V|{proportional_to}{eta}{sup 2}, where the proportionality coefficient depends on the spin of the larger hole and the geometry of the system (e.g. orbital inclination). The small recoil velocity is due to cancellations; while the fraction of the total binary mass radiated away in gravitational waves is O({eta}), most of this energy is emitted during the inspiral phase where the momentum radiated integrates to zero over an orbit. Here, we show that for low but nonzero inclination prograde orbits and very rapidly spinning large holes (spin parameter a{sub *}>0.9678) the inspiralling binary can pass through resonances where the orbit-averaged radiation-reaction force is nonzero. These resonance crossings lead to a new contribution to the kick, |V|{proportional_to}{eta}{sup 3/2}. For these configurations and sufficiently extreme mass ratios, this resonant recoil is dominant. While it seems doubtful that the resonant recoil will be astrophysically significant, its existence suggests caution when extrapolating the results of numerical kick results to extreme mass ratios and near-maximal spins.

Hirata, Christopher M. [Caltech M/C 350-17, Pasadena, California 91125 (United States)

2011-05-15

264

Effect of quantum therapy on pork quality

In this study the impact of quantum therapy on meat quality of slaughtered pigs was investigated. For this purpose the pigs were treated with different doses of magnet-infrared-laser (MIL) radiation. Animals were divided into four groups according to radiation doses (4096, 512, and 64 Hz, and control without application), which were applied in the lumbar area of musculus longissimus dorsi (loin) at various time intervals prior to the slaughter (14 d, 24 h, and 1 h). Animals were slaughtered and the meat quality was evaluated by determining of pH value (1, 3, and 24 h post slaughter), drip loss, colour, and lactic acid and phosphoric acid amounts. MIL therapy can be used in various fields of veterinary medicine as are surgery and orthopaedics, internal medicine, dentistry, pulmonology, gastroenterology, gynaecology, urology, nephrology, and dermatology. The results achieved showed that MIL radiation used in a short period before slaughter (1 h) can cause a change in the meat quality, as reflected by the non-standard development of pH values, increases in drip loss, and changes of meat colour. PMID:22042653

Bodnár, Martin; Nagy, Jozef; Popelka, Peter; Koréneková, Beáta; Ma?anga, Ján; Nagyová, Alena

2011-01-01

265

Photodynamic antibacterial effect of graphene quantum dots.

Synthesis of new antibacterial agents is becoming increasingly important in light of the emerging antibiotic resistance. In the present study we report that electrochemically produced graphene quantum dots (GQD), a new class of carbon nanoparticles, generate reactive oxygen species when photoexcited (470 nm, 1 W), and kill two strains of pathogenic bacteria, methicillin-resistant Staphylococcus aureus and Escherichia coli. Bacterial killing was demonstrated by the reduction in number of bacterial colonies in a standard plate count method, the increase in propidium iodide uptake confirming the cell membrane damage, as well as by morphological defects visualized by atomic force microscopy. The induction of oxidative stress in bacteria exposed to photoexcited GQD was confirmed by staining with a redox-sensitive fluorochrome dihydrorhodamine 123. Neither GQD nor light exposure alone were able to cause oxidative stress and reduce the viability of bacteria. Importantly, mouse spleen cells were markedly less sensitive in the same experimental conditions, thus indicating a fairly selective antibacterial photodynamic action of GQD. PMID:24612819

Ristic, Biljana Z; Milenkovic, Marina M; Dakic, Ivana R; Todorovic-Markovic, Biljana M; Milosavljevic, Momir S; Budimir, Milica D; Paunovic, Verica G; Dramicanin, Miroslav D; Markovic, Zoran M; Trajkovic, Vladimir S

2014-05-01

266

Stopping Power of Au for Ti Using Elastic Recoil Technique

The slowing down of heavy ions in matter is still not well understood especially at low energies (<0.5 MeV/u). In this contribution we present new experimental data for the stopping power of Au for Ti ions using an elastic recoil technique where a heavy-ion beam at low energies is produced by elastic scattering of an energetic primary beam imping on a thin target. Atoms from the target recoil at low energies. We compare our experimental data with previous data and with semi-empirical and theoretical models.

Linares, R.; Freire, J. A.; Ribas, R. V.; Medina, N. H.; Oliveira, J. R. B.; Seale, W. A.; Cybulska, E. W.; Wiedemann, K. T.; Allegro, P. R.; Toufen, D. L. [Instituto de Fisica da Universidade de Sao Paulo, C.P. 66318, 05317-970, S. Paulo, SP (Brazil)

2009-06-03

267

Computing at the Dubna gas-filled recoil separator

NASA Astrophysics Data System (ADS)

Simulation codes for the spectra of heavy implanted nuclei, applications for online data visualization and real time PC-based algorithms are considered. Special attention is paid to the application of real time techniques for radical suppression of background products in heavy-ion-induced nuclear reactions at the U-400 cyclotron of the Flerov Laboratory of Nuclear Reactions. The detection system of the Dubna gas-filled recoil separator (DGFRS) is also briefly described. Calculated heavy recoil spectra are compared with those measured in heavy-ion-induced nuclear reactions.

Tsyganov, Yuri S.; Polyakov, Alexandr N.

2006-03-01

268

Observation of quantum Talbot effect from a domain-engineered nonlinear photonic crystal

NASA Astrophysics Data System (ADS)

The quantum Talbot effect is observed from a domain-engineered nonlinear photonic crystal dispensing with a real grating. We deduce and experimentally verify the quantum self-imaging formula which is related to the crystal's structure parameter and working wavelengths. A two-photon Talbot carpet is captured to characterize the Fresnel diffraction dynamics of entangled photons wherein the quantum fractional Talbot effect is specified. The compact and stable quantum Talbot effect can be considered as the contactless diagnosis of domain's homogeneity and developed for new types of entangled photon source and quantum technologies such as quantum lithography with improved performance.

Jin, H.; Xu, P.; Zhao, J. S.; Leng, H. Y.; Zhong, M. L.; Zhu, S. N.

2012-11-01

269

Recoil-alpha-fission and recoil-alpha-alpha-fission events observed in the reaction Ca-48 + Am-243

Products of the fusion-evaporation reaction Ca-48 + Am-243 were studied with the TASISpec set-up at the gas-filled separator TASCA at the GSI Helmholtzzentrum f\\"ur Schwerionenforschung. Amongst the detected thirty correlated alpha-decay chains associated with the production of element Z=115, two recoil-alpha-fission and five recoil-alpha-alpha-fission events were observed. The latter are similar to four such events reported from experiments performed at the Dubna gas-filled separator. Contrary to their interpretation, we propose an alternative view, namely to assign eight of these eleven decay chains of recoil-alpha(-alpha)-fission type to start from the 3n-evaporation channel 115-288. The other three decay chains remain viable candidates for the 2n-evaporation channel 115-289.

Forsberg, U; Andersson, L -L; Di Nitto, A; Düllmann, Ch E; Gates, J M; Golubev, P; Gregorich, K E; Gross, C J; Herzberg, R -D; Hessberger, F P; Khuyagbaatar, J; Kratz, J V; Rykaczewski, K; Sarmiento, L G; Schädel, M; Yakushev, A; Åberg, S; Ackermann, D; Block, M; Brand, H; Carlsson, B G; Cox, D; Derkx, X; Dobaczewski, J; Eberhardt, K; Even, J; Fahlander, C; Gerl, J; Jäger, E; Kindler, B; Krier, J; Kojouharov, I; Kurz, N; Lommel, B; Mistry, A; Mokry, C; Nazarewicz, W; Nitsche, H; Omtvedt, J P; Papadakis, P; Ragnarsson, I; Runke, J; Schaffner, H; Schausten, B; Shi, Y; Thörle-Pospiech, P; Torres, T; Traut, T; Trautmann, N; Türler, A; Ward, A; Ward, D E; Wiehl, N

2015-01-01

270

Recoil-alpha-fission and recoil-alpha-alpha-fission events observed in the reaction Ca-48 + Am-243

Products of the fusion-evaporation reaction Ca-48 + Am-243 were studied with the TASISpec set-up at the gas-filled separator TASCA at the GSI Helmholtzzentrum f\\"ur Schwerionenforschung. Amongst the detected thirty correlated alpha-decay chains associated with the production of element Z=115, two recoil-alpha-fission and five recoil-alpha-alpha-fission events were observed. The latter are similar to four such events reported from experiments performed at the Dubna gas-filled separator. Contrary to their interpretation, we propose an alternative view, namely to assign eight of these eleven decay chains of recoil-alpha(-alpha)-fission type to start from the 3n-evaporation channel 115-288. The other three decay chains remain viable candidates for the 2n-evaporation channel 115-289.

U. Forsberg; D. Rudolph; L. -L. Andersson; A. Di Nitto; Ch. E. Düllmann; J. M. Gates; P. Golubev; K. E. Gregorich; C. J. Gross; R. -D. Herzberg; F. P. Hessberger; J. Khuyagbaatar; J. V. Kratz; K. Rykaczewski; L. G. Sarmiento; M. Schädel; A. Yakushev; S. Åberg; D. Ackermann; M. Block; H. Brand; B. G. Carlsson; D. Cox; X. Derkx; J. Dobaczewski; K. Eberhardt; J. Even; C. Fahlander; J. Gerl; E. Jäger; B. Kindler; J. Krier; I. Kojouharov; N. Kurz; B. Lommel; A. Mistry; C. Mokry; W. Nazarewicz; H. Nitsche; J. P. Omtvedt; P. Papadakis; I. Ragnarsson; J. Runke; H. Schaffner; B. Schausten; Y. Shi; P. Thörle-Pospiech; T. Torres; T. Traut; N. Trautmann; A. Türler; A. Ward; D. E. Ward; N. Wiehl

2015-02-10

271

Quantum spin Hall (QSH) effect materials feature edge states that are topologically protected from backscattering. However, the small band gap in materials that have been identified as QSH insulators limits applications. ...

Qian, Xiaofeng

272

Negative muon chemistry: the quantum muon effect and the finite nuclear mass effect.

The any-particle molecular orbital method at the full configuration interaction level has been employed to study atoms in which one electron has been replaced by a negative muon. In this approach electrons and muons are described as quantum waves. A scheme has been proposed to discriminate nuclear mass and quantum muon effects on chemical properties of muonic and regular atoms. This study reveals that the differences in the ionization potentials of isoelectronic muonic atoms and regular atoms are of the order of millielectronvolts. For the valence ionizations of muonic helium and muonic lithium the nuclear mass effects are more important. On the other hand, for 1s ionizations of muonic atoms heavier than beryllium, the quantum muon effects are more important. In addition, this study presents an assessment of the nuclear mass and quantum muon effects on the barrier of He? + H2 reaction. PMID:25188920

Posada, Edwin; Moncada, Félix; Reyes, Andrés

2014-10-01

273

Evanescent radiation, quantum mechanics and the Casimir effect

NASA Technical Reports Server (NTRS)

An attempt to bridge the gap between classical and quantum mechanics and to explain the Casimir effect is presented. The general nature of chaotic motion is discussed from two points of view: the first uses catastrophe theory and strange attractors to describe the deterministic view of this motion; the underlying framework for chaos in these classical dynamic systems is their extreme sensitivity to initial conditions. The second interpretation refers to randomness associated with probabilistic dynamics, as for Brownian motion. The present approach to understanding evanescent radiation and its relation to the Casimir effect corresponds to the first interpretation, whereas stochastic electrodynamics corresponds to the second viewpoint. The nonlinear behavior of the electromagnetic field is also studied. This well-understood behavior is utilized to examine the motions of two orbiting charges and shows a closeness between the classical behavior and the quantum uncertainty principle. The evanescent radiation is used to help explain the Casimir effect.

Schatten, Kenneth H.

1989-01-01

274

Magnetic quantum ratchet effect in Si-MOSFETs.

We report on the observation of magnetic quantum ratchet effect in metal-oxide semiconductor field-effect-transistors on silicon surface (Si-MOSFETs). We show that the excitation of an unbiased transistor by ac electric field of terahertz radiation at normal incidence leads to a direct electric current between the source and drain contacts if the transistor is subjected to an in-plane magnetic field. The current rises linearly with the magnetic field strength and quadratically with the ac electric field amplitude. It depends on the polarization state of the ac field and can be induced by both linearly and circularly polarized radiation. We present the quasi-classical and quantum theories of the observed effect and show that the current originates from the Lorentz force acting upon carriers in asymmetric inversion channels of the transistors. PMID:24888735

Ganichev, S D; Tarasenko, S A; Karch, J; Kamann, J; Kvon, Z D

2014-06-25

275

Simple computer model for the quantum Zeno effect

This paper presents a simple model for repeated measurement of a quantum system: the evolution of a free particle, simulated by discretising the particle's position. This model is easily simulated by computer and provides a useful arena to investigate the effects of measurement upon dynamics, in particular the slowing of evolution due to measurement (the `quantum Zeno effect'). The results of this simulation are discussed for two rather different sorts of measurement process, both of which are (simplified forms of) measurements used in previous simulations of position measurement. A number of interesting results due to measurement are found, and the investigation casts some light on previous disagreements about the presence or absence of the Zeno effect.

David Wallace

2000-07-04

276

Memory effects in attenuation and amplification quantum processes

With increasing communication rates via quantum channels, memory effects become unavoidable whenever the use rate of the channel is comparable to the typical relaxation time of the channel environment. We introduce a model of a bosonic memory channel, describing correlated noise effects in quantum-optical processes via attenuating or amplifying media. To study such a channel model, we make use of a proper set of collective field variables, which allows us to unravel the memory effects, mapping the n-fold concatenation of the memory channel to a unitarily equivalent, direct product of n single-mode bosonic channels. We hence estimate the channel capacities by relying on known results for the memoryless setting. Our findings show that the model is characterized by two different regimes, in which the cross correlations induced by the noise among different channel uses are either exponentially enhanced or exponentially reduced.

Cosmo Lupo; Vittorio Giovannetti; Stefano Mancini

2010-10-05

277

Quantum electrodynamic effects in finite space

NASA Astrophysics Data System (ADS)

The modifications of various quantum properties due to a discrete structure of the modes of the vacuum electromagnetic field are discussed. In contrast to the usual case of a continuous spectrum of the free space fluctuations, we consider physical systems in a resonator or in a wave guide. It is shown that the relaxation time of the system can be increased ot decreased, by increasing or decreasing the density of modes with respect to the case of unperturbed vacuum. On the other hand, we predict level shifts due to the reduced mass of the electron and deviations from the Lambshift for hydrogen in a wave guide, which can be detected with the presently feasible high resolution spectroscopy. We propose an experimental set-up. Nous discutons les modifications de diverses propriétés quantiques sous l'influence d'une structure de modes discrets du champ électromagnétique dans le vide. En comparaison du cas habituel d'un spectre continu des fluctuations du vide dans l'espace libre, nous considérons ici des systèmes physiques dans un résonateur ou un guide d'ondes. Il est démontré que le temps de relaxation du système peut être prolongé ou raccourci, ceci en augmentant ou diminuant la densité des modes par rapport à sa valeur dans le vide non-perturbé. D'autre part, nous prédisons des déplacements de niveau dus à la masse réduite de l'électron et des déviations du Lamb shift pour des atomes d'hydrogène dans un guide d'ondes, qui peuvent être détectées grâce à la haute résolution accessible actuellement en spectroscopie. Nous présentons un dispositif expérimental.

Dobiasch, P.; Walther, H.

278

Loop quantum cosmology of Bianchi IX: Effective dynamics

We study numerically the solutions to the effective equations of Bianchi IX spacetimes within Loop Quantum Cosmology. We consider Bianchi IX models with and without inverse triad corrections whose matter content is a scalar field without mass. The solutions are classified using the classical observables. We show that both effective theories --with lapse N=V and N=1-- solve the big bang singularity and reproduce the classical dynamics far from the bounce. Moreover, due to the spatial compactness, there is an infinity number of bounces and recollapses. We study the limit of large volume and show that both effective theories reproduce the same dynamics, thus recovering general relativity. We implement a procedure to identify amongst the Bianchi IX solutions, those that behave like k=0,1 FLRW as well as Bianchi I, II, and VII_0 models. The effective solutions exhibit Bianchi I phases with Bianchi II transitions and also Bianchi VII_0 phases, which had not been studied before, at the quantum nor effective level. We comment on the possible implications of these results for a quantum modification to the classical BKL behaviour.

Alejandro Corichi; Edison Montoya

2015-02-09

279

We investigate the excitonic optical properties in thin quantum boxes in the intermediate regime between the two-dimensional (2D) and zero-dimensional (0D) with a theoretical analysis that rigorously treats excitonic confinement effects. It is found that the exciton binding energy is substantially enhanced and that the oscillator strength concentrates to the lowest excitonic transition, even in a thin box whose lateral

Hideki Gotoh; Hiroaki Ando

1997-01-01

280

Band-edge electroabsorption in quantum well structures - The quantum-confined Stark effect

Theory and extended experimental results are presented for the large shift in optical absorption in GaAs-AlGaAs quantum-well structures with electric field perpendicular to the layers. In contrast to the Stark effect on atoms or on excitons in bulk semiconductors, the exciton resonances remain resolved even for shifts much larger than the zero-field binding energy and fields more than 50 times

D. A. B. Miller; D. S. Chemla; T. C. Damen; T. H. Wood; C. A. Burrus; A. C. Gossard; W. Wiegmann

1984-01-01

281

SO(5) symmetry in the quantum Hall effect in graphene

NASA Astrophysics Data System (ADS)

Electrons in graphene have four flavors associated with low-energy spin and valley degrees of freedom. The fractional quantum Hall effect in graphene is dominated by long-range Coulomb interactions, which are invariant under rotations in spin-valley space. This SU(4) symmetry is spontaneously broken at most filling factors, and also weakly broken by atomic scale valley-dependent and valley-exchange interactions with coupling constants gz and g?. In this paper, we demonstrate that when gz=-g? , an exact SO(5) symmetry survives which unifies the Néel spin order parameter of the antiferromagnetic state and the X Y valley order parameter of the Kekulé distortion state into a single five-component order parameter. The proximity of the highly insulating quantum Hall state observed in graphene at ? =0 to an ideal SO(5) symmetric quantum Hall state remains an open experimental question. We illustrate the physics associated with this SO(5) symmetry by studying the multiplet structure and collective dynamics of filling factor ? =0 quantum Hall states based on exact-diagonalization and low-energy effective theory approaches. This allows to illustrate how manifestations of the SO(5) symmetry would survive even when it is weakly broken.

Wu, Fengcheng; Sodemann, Inti; Araki, Yasufumi; MacDonald, Allan H.; Jolicoeur, Thierry

2014-12-01

282

NASA Astrophysics Data System (ADS)

Silicene is a monolayer of silicon atoms forming a two-dimensional honeycomb lattice, which shares almost every remarkable property with graphene. The low energy dynamics is described by Dirac electrons, but they are massive due to relatively large spin-orbit interactions. I will explain the following properties of silicene: 1) The band structure is controllable by applying an electric field. 2) Silicene undergoes a phase transition from a topological insulator to a band insulator by applying external electric field. 3) The topological phase transition can be detected experimentally by way of diamagnetism. 4) There is a novel valley-spin selection rules revealed by way of photon absorption. 5) Silicene yields a remarkably many phases such as quantum anomalous Hall phase and valley polarized metal when the exchange field is additionally introduced. 6) A silicon nanotubes can be used to convey spin currents under an electric field.

Ezawa, Motohiko

2013-12-01

283

Silicene is a monolayer of silicon atoms forming a two-dimensional honeycomb lattice, which shares almost every remarkable property with graphene. The low energy dynamics is described by Dirac electrons, but they are massive due to relatively large spin-orbit interactions. I will explain the following properties of silicene: 1) The band structure is controllable by applying an electric field. 2) Silicene undergoes a phase transition from a topological insulator to a band insulator by applying external electric field. 3) The topological phase transition can be detected experimentally by way of diamagnetism. 4) There is a novel valley-spin selection rules revealed by way of photon absorption. 5) Silicene yields a remarkably many phases such as quantum anomalous Hall phase and valley polarized metal when the exchange field is additionally introduced. 6) A silicon nanotubes can be used to convey spin currents under an electric field.

Ezawa, Motohiko [Department of Applied Physics, University of Tokyo, Hongo 7-3-1, Tokyo 113-8656 (Japan)

2013-12-04

284

Packet narrowing and quantum entanglement in photoionization and photodissociation

The narrowing of electron and ion wave packets in the process of photoionization is investigated, with the electron-ion recoil fully taken into account. Packet localization of this type is directly related to entanglement in the joint quantum state of electron and ion, and to Einstein-Podolsky-Rosen localization. Experimental observation of such packet-narrowing effects is suggested via coincidence registration by two detectors, with a fixed position of one and varying position of the other. A similar effect, typically with an enhanced degree of entanglement, is shown to occur in the case of photodissociation of molecules.

M. V. Fedorov; M. A. Efremov; A. E. Kazakov; K. W. Chan; C. K. Law; J. H. Eberly

2003-12-13

285

Relativistic Doppler effect in quantum communication

When an electromagnetic signal propagates in vacuo, a polarization detector cannot be rigorously perpendicular to the wave vector because of diffraction effects. The vacuum behaves as a noisy channel, even if the detectors are perfect. The ``noise'' can however be reduced and nearly cancelled by a relative motion of the observer toward the source. The standard definition of a reduced density matrix fails for photon polarization, because the transversality condition behaves like a superselection rule. We can however define an effective reduced density matrix which corresponds to a restricted class of positive operator-valued measures. There are no pure photon qubits, and no exactly orthogonal qubit states.

Asher Peres; Daniel R. Terno

2003-04-06

286

A Candidate Recoiling Black Hole in a Nearby Dwarf Galaxy

NASA Astrophysics Data System (ADS)

We have discovered a BH recoil candidate offset by 800 pc from a nearby dwarf galaxy. The object, SDSS1133, shows offset broad lines and strong variability. While originally classified as a supernova because of its non-detection in 2005, we detect it in recent and past observations over 63 years. Using high-resolution adaptive optics observations, we constrain the source emission region to be <12 pc. Overall these properties are consistent with theoretical predictions for a runaway BH ejected from its host by gravitational-wave recoil following a merger. We propose a small, 4 orbit HST observation using the COS spectrograph in the FUV, to test for broad C IV emission and other high ionization emission lines which would decisively favor the recoiling BH interpretation. The unique UV spectroscopic capability of HST is critical to decide whether this is a recoiling black hole or an unprecedented 50 year outbursting LBV star (e.g. Eta Carina) followed by a unique long duration SN IIn with rebrightening. Either discovery would be extremely exciting. Finally, SDSS1133 has recently undergone a 1.3 mag rebrightening in PanSTARRS imaging suggesting that the coming year is a critical time to observe the source at maximum.

Koss, Michael

2014-10-01

287

Status and Prospects of the HERMES Recoil Detector

/Scintillator sandwich Fiber Detector (SFT) 2 barrels with 4 layers of scintillating fibers 2 parallel and 2 stereo SFT Particle Identification 8HERMES Recoil Detector A. Mussgiller, SPIN 2008, 10/10/08 SSDV /c : SSD & SFT & PDp ~0.6 GeV /c #12; Particle Identification (p > 0

288

Scintillation response of liquid xenon to low energy nuclear recoils

NASA Astrophysics Data System (ADS)

Liquid Xenon (LXe) is expected to be an excellent target and detection medium to search for dark matter in the form of Weakly Interacting Massive Particles (WIMPs). We have measured the scintillation efficiency of nuclear recoils with kinetic energy between 10.4 and 56.5 keV relative to that of 122 keV gamma rays from C57o. The scintillation yield of 56.5 keV recoils was also measured as a function of applied electric field, and compared to that of gamma rays and alpha particles. The Xe recoils were produced by elastic scattering of 2.4 MeV neutrons in liquid xenon at a variety of scattering angles. The relative scintillation efficiency is 0.130±0.024 and 0.227±0.016 for the lowest and highest energy recoils, respectively. This is about 15% less than the value predicted by Lindhard, based on nuclear quenching. Our results are in good agreement with more recent theoretical predictions that consider the additional reduction of scintillation yield due to biexcitonic collisions in LXe.

Aprile, E.; Giboni, K. L.; Majewski, P.; Ni, K.; Yamashita, M.; Hasty, R.; Manzur, A.; McKinsey, D. N.

2005-10-01

289

Scintillation response of liquid xenon to low energy nuclear recoils

Liquid Xenon (LXe) is expected to be an excellent target and detection medium to search for dark matter in the form of Weakly Interacting Massive Particles (WIMPs). We have measured the scintillation efficiency of nuclear recoils with kinetic energy between 10.4 and 56.5 keV relative to that of 122 keV gamma rays from {sup 57}Co. The scintillation yield of 56.5 keV recoils was also measured as a function of applied electric field, and compared to that of gamma rays and alpha particles. The Xe recoils were produced by elastic scattering of 2.4 MeV neutrons in liquid xenon at a variety of scattering angles. The relative scintillation efficiency is 0.130{+-}0.024 and 0.227{+-}0.016 for the lowest and highest energy recoils, respectively. This is about 15% less than the value predicted by Lindhard, based on nuclear quenching. Our results are in good agreement with more recent theoretical predictions that consider the additional reduction of scintillation yield due to biexcitonic collisions in LXe.

Aprile, E.; Giboni, K.L.; Majewski, P.; Ni, K.; Yamashita, M.; Hasty, R.; Manzur, A.; McKinsey, D.N. [Physics Department and Astrophysics Laboratory, Columbia University, New York, New York 10027 (United States); Department of Physics, Yale University, P.O. Box 208120, New Haven, Connecticut 06520 (United States)

2005-10-01

290

High-energy recoil implantation of boron into silicon

NASA Astrophysics Data System (ADS)

One approach to fabricate shallow junctions made of B-doped Si is to deposit B on Si, followed by knocking the B into the Si substrate with Si ions. Conventional belief is that the higher the implantation energy, the deeper the recoil profile. While this is true for low-energy incident ions, we show here that the situation is reversed for incident Si ions of higher energy due to the fact that recoil probability at a given angle is a strong function of the energy of the primary projectile. Our experiments show that 500 keV high-energy recoil implantation produces a shallower B profile than lower-energy implantation such as 10 and 50 keV. The secondary ion mass spectrometry analysis shows that the distribution of recoiled B atoms scattered by the energetic Si ions agrees with that calculated on the basis of interatomic potential suggested by W. D. Wilson, L. G. Haagmark, and J. P. Biersack [Phys. Rev. B 15, 2458 (1977)]. Sub-100 nm p+/n junctions have been realized with a 500 keV Si ion beam.

Shao, Lin; Lu, Xinming; Jin, Jianyue; Li, Qinmian; Liu, Jiarui; van der Heide, P. A. W.; Chu, Wei-Kan

2000-06-01

291

Modeling GW Recoil and the Observability of Offset Quasars

NASA Astrophysics Data System (ADS)

The merger of two supermassive black holes (SMBHs) imparts a gravitational-wave (GW) recoil kick to the remnant SMBH. In extreme cases these kicks may be thousands of km/s -- enough to easily eject them from their host galaxies. Moderate recoil kicks may also influence the co-evolution of SMBHs and galaxies. Moreover, an accreting, kicked SMBH may be observable for up to tens of Myr as an offset quasar. Prior to the advent of a space-based GW observatory, detections of offset quasars may offer the best chance for identifying recent SMBH mergers. Already, observational searches for recoiling quasars have identified several candidates. I will review this progress and also describe efforts to model the observable population of recoiling quasars in a cosmological framework, including a physically-motivated, time-dependent model for accretion onto kicked BHs. I will discuss the expected prospects for observing spatially- or kinematically-offset quasars via dedicated searches, as well as the empirical constraints that such detections might place on the spin distribution of the progenitor BHs.

Blecha, Laura

292

Accurate Simulations of Pb Recoils in SuperCDMS

NASA Astrophysics Data System (ADS)

SuperCDMS is a direct detection search for WIMPs, currently operating a 9 kg array of germanium detectors in the Soudan Underground Laboratory. The detectors, known as iZIPs, are cylindrical in shape and each flat surface is instrumented with both ionization and phonon sensors. Charge and phonon information is collected for each event, and comparing the energy collected in the phonon sensors to the charge sensors gives excellent discrimination power between nuclear recoil and electron recoil events. Furthermore, this technology provides excellent discrimination between surface and bulk events. In order to show the surface event rejection capability of these detectors, two Pb sources were installed facing two of the detectors currently operating in the Soudan experimental run. The Pb decays to Bi, which in turn decays to Po. The Po decays by alpha emission, yielding a recoiling Pb ion with 103 keV kinetic energy and an alpha particle with 5.4 MeV kinetic energy. We used the non-standard Screened Nuclear Recoil Physics List (Mendenhall and Weller, Nucl. Instrum. Methods Phys. Res. B 227:420-430, 2005) in Geant4 (Agostinelli et al., Nucl. Instrum. Methods Phys. Res. Sect. A 506:250-303, 2003) to simulate all of the above decays and achieve excellent agreement with experiment. The focus of this paper is the simulation of the Po decay.

Redl, P.

2014-09-01

293

Proton recoil detector of fusion neutrons using natural diamond

NASA Astrophysics Data System (ADS)

Diamond, with its high radiation damage resistance, is an attractive alternative to silicon for neutron measurements in next step fusion experiments. A 200-?m-thick type IIa natural diamond with Ti/Au contacts was tested at the LAMPF-WNR facility by time-of-flight neutron energy identification. The crystal, having a carrier lifetime of up to 1 ns, was arranged in a low-energy-resolution, high-sensitivity proton recoil telescope consisting of a polyethylene radiator and a low-energy-proton Teflon filter. This arrangement is similar to the triton burnup monitor of Croft et al. [Rev. Sci. Instrum. 64, 1418 (1993)], where a silicon photodiode was used as a recoil proton detector. The observed sensitivity for 14 MeV neutrons (DT) is (1.25±0.15)×10-3 counts/neutron. However, a high contribution of neutron-induced events in the diamond, mainly carbon (A=12) recoils, was observed. A one-dimensional calculation for the detector response to carbon recoil and proton deposition is compared to the measurements. Poor energy resolution of the diamond detector precludes pulse height discrimination between direct 2.5 MeV neutrons events and proton events corresponding to 14 MeV neutrons. Therefore, an overall DT/DD neutron sensitivity ratio of only ˜6.5 is achieved. This value is much lower than the ratio of 540 reported by Croft et al. in their silicon (A=28) monitor.

Maqueda, R. J.; Barnes, Cris W.; Han, S. S.; Staples, P. A.; Wagner, R. S.

1997-01-01

294

Quantum effect on parametric dispersion in presence of nonuniform size colloids in semiconductors

Quantum effect on parametric dispersion characteristics in ion implanted semiconductors in presence of nonuniform size colloids is analytically investigated in the present report. Nonuniform size colloids are managed through polynomial distribution function in the analysis. Here the used quantum hydrodynamic model is described by a set of hydrodynamic equations (typically continuity and momentum transfer) that include quantum effects via Bohm

R Vanshpal; S Dubey; S Ghosh

2012-01-01

295

Physica Scripta. Vol. T59, 286-293, 1995 Quantum Effects in Measurements on Trapped Ions``

as far as Bohr's model of the atom and the idea that tran- sitions between atomic states take place, 1995 Abstract Quantum mechanical effects which are manifested in measurements on trapped atomic ions of atomic ion lifetimes and spectra, detection of antibunching of light, the quantum Zeno effect and quantum

296

Fractional Josephson effect in a quadruple quantum dot

NASA Astrophysics Data System (ADS)

A double quantum dot coupled to an s-wave superconductor and subject to an inhomogeneous magnetic field can host a pair of zero-energy Majorana fermions when the dot properties are tuned appropriately. Here, we demonstrate the possibility of generating a fractional 4? Josephson effect in two such double dots tunnel-coupled to each other. We discuss the robustness of this effect with respect to perturbations away from the special point in parameter space where the uncoupled double dots host Majorana fermions. We demonstrate the possibility of generating Josephson effects with a period of 8? and 12? in strongly coupled double dots.

Sothmann, Björn; Li, Jian; Büttiker, Markus

2013-08-01

297

Quantum Hall effect of Haldane model under magnetic field

NASA Astrophysics Data System (ADS)

Haldane model can realize the anomalous quantum Hall effect (QHE) without Landau levels (LLs) and serves as a prototype of the quantum spin Hall effect. In this paper, we study the QHE of Haldane model under magnetic field with magnitude such that the magnetic flux in a plaquette is commensurate with the lattice structure. First, we show the origin of unconventional QHE in graphene and point out a general rule for the Hall step of Dirac fermions, which strongly depends on the valley degeneracy of each LL. Second, we study the conductance around the neutral point which lies in the gap given by continuous bands, revealing the competition between periodic magnetic flux and uniform magnetic field. Moreover, the redistribution behavior of Chern number is investigated. We find that besides the staggered magnetic flux, the next-nearest-neighbor hopping can also induce the redistribution. We also study the QHE of the extended Haldane model on a square lattice.

Wang, Yi-Xiang; Li, Fu-Xiang; Wu, Ya-Min

2014-01-01

298

Quantum Hall Effect, Bosonization and Chiral Actions in Higher Dimensions

NASA Astrophysics Data System (ADS)

We give a brief review of the Quantum Hall effect in higher dimensions and its relation to fuzzy spaces. For a quantum Hall system, the lowest Landau level dynamics is given by a one-dimensional matrix action. This can be used to write down a bosonized noncommutative field theory describing the interactions of higher dimensional nonrelativistic fermions with abelian or nonabelian gauge fields in the lowest Landau level. This general approach is applied explicitly to the case of QHE on CPk. It is shown that in the semiclassical limit the effective action contains a bulk Chern-Simons type term whose anomaly is exactly canceled by a boundary term given in terms of a chiral, gauged Wess-Zumino-Witten action suitably generalized to higher dimensions.

Karabali, Dimitra

2013-12-01

299

Charge fractionalization in the integer quantum Hall effect.

We report an observation, via sensitive shot noise measurements, of charge fractionalization of chiral edge electrons in the integer quantum Hall effect regime. Such fractionalization results solely from interchannel Coulomb interaction, leading electrons to decompose to excitations carrying fractional charges. The experiment was performed by guiding a partitioned current carrying edge channel in proximity to another unbiased edge channel, leading to shot noise in the unbiased edge channel without net current, which exhibited an unconventional dependence on the partitioning. The determination of the fractional excitations, as well as the relative velocities of the two original (prior to the interaction) channels, relied on a recent theory pertaining to this measurement. Our result exemplifies the correlated nature of multiple chiral edge channels in the integer quantum Hall effect regime. PMID:24815662

Inoue, Hiroyuki; Grivnin, Anna; Ofek, Nissim; Neder, Izhar; Heiblum, Moty; Umansky, Vladimir; Mahalu, Diana

2014-04-25

300

Effect of donor impurity dislocation in elliptical quantum rings

NASA Astrophysics Data System (ADS)

We investigate the effect of an off-center donor impurity on the electronic properties of a two-dimensional quantum ring with a deformed geometrical structure in the form of an ellipse. It is shown that the dislocation of impurity from the center of elliptical quantum ring opens sizable gaps in the energy spectrum and largely deforms the eigenenergies near the ground state. As a result, the Aharonov-Bohm oscillations are quenched and the persistent electron current decreases intensely. Moreover, we show that the ground state energy exhibits a local extremum when the donor impurity is located on semi-minor (or -major) axis of the elliptic ring. The effects of the eccentricity of elliptical ring on the energy spectra and persistent current are also studied.

Khajeh Salehani, Hojjatollah; Shakouri, Khosrow; Esmaeilzadeh, Mahdi

2015-02-01

301

Heat capacity of water: A signature of nuclear quantum effects

NASA Astrophysics Data System (ADS)

In this note we present results for the heat capacity at constant pressure for the TIP4PQ/2005 model, as obtained from path-integral simulations. The model does a rather good job of describing both the heat capacity of ice Ih and of liquid water. Classical simulations using the TIP4P/2005, TIP3P, TIP4P, TIP4P-Ew, simple point charge/extended, and TIP5P models are unable to reproduce the heat capacity of water. Given that classical simulations do not satisfy the third law of thermodynamics, one would expect such a failure at low temperatures. However, it seems that for water, nuclear quantum effects influence the heat capacities all the way up to room temperature. The failure of classical simulations to reproduce Cp points to the necessity of incorporating nuclear quantum effects to describe this property accurately.

Vega, C.; Conde, M. M.; McBride, C.; Abascal, J. L. F.; Noya, E. G.; Ramirez, R.; Sesé, L. M.

2010-01-01

302

Topological domain walls and quantum valley Hall effects in silicene

NASA Astrophysics Data System (ADS)

Silicene is a two-dimensional honeycomb lattice made of silicon atoms, which is considered to be a new Dirac fermion system. Based on first-principles calculations, we examine the possibility of the formation of solitonlike topological domain walls (DWs) in silicene. We show that the DWs between regions of distinct ground states of the buckled geometry should bind electrons when a uniform electric field is applied in the perpendicular direction to the sheet. The topological origin of the electron confinement is demonstrated based on numerical calculations of the valley-specific Hall conductivities, and possible experimental signatures of the quantum valley Hall effects are discussed using simulated scanning tunneling microscopy images. Our results strongly suggest that silicene could be an ideal host for the quantum valley Hall effect, thus providing a pathway to the valleytronics in silicon-based technology.

Kim, Youngkuk; Choi, Keunsu; Ihm, Jisoon; Jin, Hosub

2014-02-01

303

Efficient semiclassical quantum nuclear effects for shock compression studies

NASA Astrophysics Data System (ADS)

A fast methodology is described for atomistic simulations of shock-compressed materials that incorporates quantum nuclear effects in a self-consistent fashion. We introduce a modification of the multiscale shock technique (MSST) that couples to a quantum thermal bath described by a colored noise Langevin thermostat. The new approach, which we call QB-MSST, is of comparable computational cost to MSST and self-consistently incorporates quantum heat capacities and Bose-Einstein harmonic vibrational distributions. As a first test, we study shock-compressed methane using the ReaxFF potential. The Hugoniot curves predicted from the new approach are found comparable with existing experimental data. We find that the self-consistent nature of the method results in the onset of chemistry at 40% lower pressure on the shock Hugoniot than observed with classical molecular dynamics. The temperature shift associated with quantum heat capacity is determined to be the primary factor in this shift.[4pt] In collaboration with Tingting Qi, Department of Materials Science and Engineering, Stanford University.

Reed, Evan

2013-03-01

304

High speed quantum-well lasers and carrier transport effects

Carrier transport can significantly affect the high-speed properties of quantum-well lasers. The authors have developed a model and derived analytical expressions for the modulation response, resonance frequency, damping rate, and K factor to include these effects. They show theoretically and experimentally that carrier transport can lead to significant low-frequency parasitic-like rolloff that reduces the modulation response by as much as

Radhakrishnan Nagarajan; Masayuki Ishikawa; Toru Fukushima; Randall S. Geels; John E. Bowers

1992-01-01

305

Shell effects in quantum dots: A semiclassical approach

NASA Astrophysics Data System (ADS)

We present a self-consistent Thomas-Fermi (TF) analysis of confined fermions with interactions in two dimensions. While the formalism may be developed for arbitrary forms of two-body interactions, we show that the TF model with logarithmic interactions is in fact an exactly solvable model. Furthermore, we show that the quantum corrections to the Thomas-Fermi energies reproduce the main features, namely the shell effects, seen in recent experiments.

Sinha, Subhasis; Shankar, R.; Murthy, M. V. N.

2000-10-01

306

Investigation of Thermal Effects in Quantum-Cascade Lasers

The development of a thermal model for quantum cascade lasers (QCLs) is presented. The model is used in conjunc- tion with a self-consistent scattering rate calculation of the electron dynamics of an InGaAs-AlAsSb QCL to calculate the temperature distribution throughout the device which can be a limiting factor for high temperature operation. The model is used to investigate the effects

C. A. Evans; V. D. Jovanovic; Dragan Indjin; Zoran Ikonic; Paul Harrison

2006-01-01

307

Quantum amplification effect in a horizon fluctuation

The appearance of a few unevenly spaced bright flashes of light on top of Hawking radiation is the sign of the amplification effect in black hole horizon fluctuations. Previous studies on this problem suffer from the lack of considering all emitted photons in the theoretical spectroscopy of these fluctuations. In this paper, we include all of the physical transition weights and present a consistent intensity formula. This modifies a black hole radiation pattern.

Ansari, Mohammad H. [Department of Combinatorics and Optimization, University of Waterloo, Waterloo, Ontario, N2L 3G1 (Canada)

2010-05-15

308

The mechanics of elastic loading and recoil in anuran jumping.

Many animals use catapult mechanisms to produce extremely rapid movements for escape or prey capture, resulting in power outputs far beyond the limits of muscle. In these catapults, muscle contraction loads elastic structures, which then recoil to release the stored energy extremely rapidly. Many arthropods employ anatomical 'catch mechanisms' to lock the joint in place during the loading period, which can then be released to allow joint motion via elastic recoil. Jumping vertebrates lack a clear anatomical catch, yet face the same requirement to load the elastic structure prior to movement. There are several potential mechanisms to allow loading of vertebrate elastic structures, including the gravitational load of the body, a variable mechanical advantage, and moments generated by the musculature of proximal joints. To test these hypothesized mechanisms, we collected simultaneous 3D kinematics via X-ray Reconstruction of Moving Morphology (XROMM) and single-foot forces during the jumps of three Rana pipiens. We calculated joint mechanical advantage, moment and power using inverse dynamics at the ankle, knee, hip and ilio-sacral joints. We found that the increasing proximal joint moments early in the jump allowed for high ankle muscle forces and elastic pre-loading, and the subsequent reduction in these moments allowed the ankle to extend using elastic recoil. Mechanical advantage also changed throughout the jump, with the muscle contracting against a poor mechanical advantage early in the jump during loading and a higher mechanical advantage late in the jump during recoil. These 'dynamic catch mechanisms' serve to resist joint motion during elastic loading, then allow it during elastic recoil, functioning as a catch mechanism based on the balance and orientation of forces throughout the limb rather than an anatomical catch. PMID:25520385

Astley, Henry C; Roberts, Thomas J

2014-12-15

309

Absolute absorption cross sections from photon recoil in a matter-wave interferometer.

We measure the absolute absorption cross section of molecules using a matter-wave interferometer. A nanostructured density distribution is imprinted onto a dilute molecular beam through quantum interference. As the beam crosses the light field of a probe laser some molecules will absorb a single photon. These absorption events impart a momentum recoil which shifts the position of the molecule relative to the unperturbed beam. Averaging over the shifted and unshifted components within the beam leads to a reduction of the fringe visibility, enabling the absolute absorption cross section to be extracted with high accuracy. This technique is independent of the molecular density, it is minimally invasive and successfully eliminates many problems related to photon cycling, state mixing, photobleaching, photoinduced heating, fragmentation, and ionization. It can therefore be extended to a wide variety of neutral molecules, clusters, and nanoparticles. PMID:25014795

Eibenberger, Sandra; Cheng, Xiaxi; Cotter, J P; Arndt, Markus

2014-06-27

310

Absolute Absorption Cross Sections from Photon Recoil in a Matter-Wave Interferometer

NASA Astrophysics Data System (ADS)

We measure the absolute absorption cross section of molecules using a matter-wave interferometer. A nanostructured density distribution is imprinted onto a dilute molecular beam through quantum interference. As the beam crosses the light field of a probe laser some molecules will absorb a single photon. These absorption events impart a momentum recoil which shifts the position of the molecule relative to the unperturbed beam. Averaging over the shifted and unshifted components within the beam leads to a reduction of the fringe visibility, enabling the absolute absorption cross section to be extracted with high accuracy. This technique is independent of the molecular density, it is minimally invasive and successfully eliminates many problems related to photon cycling, state mixing, photobleaching, photoinduced heating, fragmentation, and ionization. It can therefore be extended to a wide variety of neutral molecules, clusters, and nanoparticles.

Eibenberger, Sandra; Cheng, Xiaxi; Cotter, J. P.; Arndt, Markus

2014-06-01

311

Absolute absorption cross sections from photon recoil in a matter-wave interferometer

We measure the absolute absorption cross section of molecules using a matter-wave interferometer. A nanostructured density distribution is imprinted onto a dilute molecular beam through quantum interference. As the beam crosses the light field of a probe laser some molecules will absorb a single photon. These absorption events impart a momentum recoil which shifts the position of the molecule relative to the unperturbed beam. Averaging over the shifted and unshifted components within the beam leads to a reduction of the fringe visibility, enabling the absolute absorption cross section to be extracted with high accuracy. This technique is independent of the molecular density, it is minimally invasive and successfully eliminates all problems related to photon-cycling, state-mixing, photo-bleaching, photo-induced heating, fragmentation and ionization. It can therefore be extended to a wide variety of neutral molecules, clusters and nanoparticles.

Sandra Eibenberger; Xiaxi Cheng; J. P. Cotter; Markus Arndt

2014-02-21

312

Absolute absorption cross sections from photon recoil in a matter-wave interferometer

We measure the absolute absorption cross section of molecules using a matter-wave interferometer. A nanostructured density distribution is imprinted onto a dilute molecular beam through quantum interference. As the beam crosses the light field of a probe laser some molecules will absorb a single photon. These absorption events impart a momentum recoil which shifts the position of the molecule relative to the unperturbed beam. Averaging over the shifted and unshifted components within the beam leads to a reduction of the fringe visibility, enabling the absolute absorption cross section to be extracted with high accuracy. This technique is independent of the molecular density, it is minimally invasive and successfully eliminates all problems related to photon-cycling, state-mixing, photo-bleaching, photo-induced heating, fragmentation and ionization. It can therefore be extended to a wide variety of neutral molecules, clusters and nanoparticles.

Eibenberger, Sandra; Cotter, J P; Arndt, Markus

2014-01-01

313

Heavy Fermion Quantum Effects in SU(2)_L Gauge Theory

We explore the effects of a heavy fermion doublet in a simplified version of the standard electroweak theory. We integrate out the doublet and compute the exact effective energy functional of spatially varying gauge and Higgs fields. We perform a variational search for a local minimum of the effective energy and do not find evidence for a soliton carrying the quantum numbers of the decoupled fermion doublet. The fermion vacuum polarization energy offsets the gain in binding energy previously argued to be sufficient to stabilize a fermionic soliton. The existence of such a soliton would have been a natural way to maintain anomaly cancellation at the level of the states. We also see that the sphaleron energy is significantly increased due to the quantum corrections of the heavy doublet. We find that when the doublet is slightly heavier than the quantum--corrected sphaleron, its decay is exponentially suppressed owing to a new barrier. This barrier exists only for an intermediate range of fermion masses, and a heavy enough doublet is indeed unstable.

E. Farhi; N. Graham; R. L. Jaffe; V. Khemani; H. Weigel

2003-03-18

314

Non-Markovianity and memory effects in quantum open systems

NASA Astrophysics Data System (ADS)

Although a number of measures for quantum non-Markovianity have been proposed recently, it is still an open question whether these measures directly characterize the memory effect of the environment, i.e., the dependence of a quantum state on its past in a time evolution. In this paper, we present a criterion and propose a measure for non-Markovianity with clear physical interpretations of the memory effect. The non-Markovianity is defined by the inequality T (t2,t0) ?T (t2,t1) T (t1,t0) in terms of memoryless dynamical map T introduced in this paper. This definition is conceptually distinct from that based on divisibility used by Rivas et al. [Phys. Rev. Lett. 105, 050403 (2010), 10.1103/PhysRevLett.105.050403], whose violation is manifested by noncomplete positivity of the dynamical map. We demonstrate via a typical quantum process that without Markovian approximation, nonzero memory effects (non-Markovianity) always exist even if the non-Markovianity is zero by the other non-Markovianity measures.

Hou, S. C.; Liang, S. L.; Yi, X. X.

2015-01-01

315

Gravitational-wave probe of effective quantum gravity

All modern routes leading to a quantum theory of gravity - i.e., perturbative quantum gravitational one-loop exact correction to the global chiral current in the standard model, string theory, and loop quantum gravity - require modification of the classical Einstein-Hilbert action for the spacetime metric by the addition of a parity-violating Chern-Simons term. The introduction of such a term leads to spacetimes that manifest an amplitude birefringence in the propagation of gravitational waves. While the degree of birefringence may be intrinsically small, its effects on a gravitational wave accumulate as the wave propagates. Observation of gravitational waves that have propagated over cosmological distances may allow the measurement of even a small birefringence, providing evidence of quantum gravitational effects. The proposed Laser Interferometer Space Antenna (LISA) will be sensitive enough to observe the gravitational waves from sources at cosmological distances great enough that interesting bounds on the Chern-Simons coupling may be found. Here we evaluate the effect of a Chern-Simons induced spacetime birefringence to the propagation of gravitational waves from such systems. Focusing attention on the gravitational waves from coalescing binary black holes systems, which LISA will be capable of observing at redshifts approaching 30, we find that the signature of Chern-Simons gravity is a time-dependent change in the apparent orientation of the binary's orbital angular momentum with respect to the observer line-of-sight, with the magnitude of change reflecting the integrated history of the Chern-Simons coupling over the worldline of the radiation wave front. While spin-orbit coupling in the binary system will also lead to an evolution of the system's orbital angular momentum, the time dependence and other details of this real effect are different than the apparent effect produced by Chern-Simons birefringence, allowing the two effects to be separately identified. In this way gravitational-wave observations with LISA may thus provide our first and only opportunity to probe the quantum structure of spacetime over cosmological distances.

Alexander, Stephon; Finn, Lee Samuel; Yunes, Nicolas [Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

2008-09-15

316

Nonlinear effects of energy band structures on optical transitions in quantum dots

The quantum theory of nonlinear effects for optical transitions of electrons in quasi-zero dimensional (Q0D) quantum dots fabricated from n-type III–V compound semiconductor materials such as n-type GaAs has been studied due to the nonparabolicity of energy band structures. We use the effective mass approximation for carriers in the quantum dots. Most realistic quantum dot systems contain the box with

Chhi-Chong Wu; Chau-Jy Lin

2002-01-01

317

Oscillating magnetocaloric effect in quantum nanoribbons

NASA Astrophysics Data System (ADS)

We investigate the oscillating magnetocaloric effect on a diamagnetic nanoribbon, using the model of a quasi-one-dimensional electron gas (Q1DEG) made with a parabolic confinement potential. We obtained analytical expressions for the thermodynamic potential and for the entropy change. The entropy change exhibits the same dependence on field and temperature observed for other diamagnetic systems. The period of the field-oscillating pattern is ~0.1 mT and the temperature of maximum entropy change is ~0.1 K with an applied field of the order of 1 T. An interesting feature of the results is the dependence of the oscillations with the strength of the confinement potential, as well as the possibility to provide a relationship among this last with nanoribbon width. In the limit of null confinement potential our expressions match those for the 2D diamagnetic system.

Alisultanov, Z. Z.; Meilanov, R. P.; Paixão, L. S.; Reis, M. S.

2015-01-01

318

A coherent understanding of low-energy nuclear recoils in liquid xenon

Liquid xenon detectors such as XENON10 and XENON100 obtain a significant fraction of their sensitivity to light (xenon for nuclear recoils also bears heavily on detector sensitivity, yet numerous measurements have not succeeded in obtaining concordant results. In this article we show that the ratio of detected ionization to scintillation can be leveraged to constrain the scintillation yield. We also present a rigorous treatment of liquid xenon detector threshold and energy resolution. Notably, the effective energy resolution differs significantly from a simple Poisson distribution. We conclude with a calculation of dark matter exclusion limits, and show that existing data from liquid xenon detectors strongly constrain recent interpretations of light dark matter.

Peter Sorensen

2010-09-07

319

Full One-Loop Supersymmetric Quantum Effects on Mw

NASA Astrophysics Data System (ADS)

We present a detailed numerical analysis of a fully-fledged computation of one-loop supersymmetric quantum effects on the mass of the weak gauge boson W± in the standard on-shell renormalization scheme based on the input parameters (GF, ?, MZ). The importance of the process-dependent contributions as compared to the universal effects is assessed. The final numerical results show that in large regions of parameter space the potential radiative shifts ? MWSUSY could be within the level of precision expected at LEP II, depending on the model considered. A comparison is made with other renormalization frameworks.

García, David; Solà, Joan

320

Time-reversal-symmetry-broken quantum spin Hall effect.

The quantum spin Hall (QSH) state of matter is usually considered to be protected by time-reversal (TR) symmetry. We investigate the fate of the QSH effect in the presence of the Rashba spin-orbit coupling and an exchange field, which break both inversion and TR symmetries. It is found that the QSH state characterized by nonzero spin Chern numbers C(±) = ±1 persists when the TR symmetry is broken. A topological phase transition from the TR-symmetry-broken QSH phase to a quantum anomalous Hall phase occurs at a critical exchange field, where the bulk band gap just closes. It is also shown that the transition from the TR-symmetry-broken QSH phase to an ordinary insulator state cannot happen without closing the band gap. PMID:21902351

Yang, Yunyou; Xu, Zhong; Sheng, L; Wang, Baigeng; Xing, D Y; Sheng, D N

2011-08-01

321

Nuclear quantum effects and hydrogen bond fluctuations in water

The hydrogen bond (HB) is central to our understanding of the properties of water. However, despite intense theoretical and experimental study, it continues to hold some surprises. Here, we show from an analysis of ab initio simulations that take proper account of nuclear quantum effects that the hydrogen-bonded protons in liquid water experience significant excursions in the direction of the acceptor oxygen atoms. This generates a small but nonnegligible fraction of transient autoprotolysis events that are not seen in simulations with classical nuclei. These events are associated with major rearrangements of the electronic density, as revealed by an analysis of the computed Wannier centers and 1H chemical shifts. We also show that the quantum fluctuations exhibit significant correlations across neighboring HBs, consistent with an ephemeral shuttling of protons along water wires. We end by suggesting possible implications for our understanding of how perturbations (solvated ions, interfaces, and confinement) might affect the HB network in water. PMID:24014589

Ceriotti, Michele; Cuny, Jérôme; Parrinello, Michele; Manolopoulos, David E.

2013-01-01

322

Dielectric function of spherical dome shells with quantum size effects.

Metallic spherical dome shells have received much attention in recent years because they have proven to possess highly impressive optical properties. The expected distinctive changes occurring owing to quantum confinement of conduction electrons in these nanoparticles as their thickness is reduced, have not been properly investigated. Here we carry out a detailed analytical derivation of the quantum contributions by introducing linearly shifted Associated Legendre Polynomials, which form an approximate orthonormal eigenbasis for the single-electron Hamiltonian of a spherical dome shell. Our analytical results clearly show the contribution of different elements of a spherical dome shell to the effective dielectric function. More specifically, our results provide an accurate, quantitative correction for the dielectric function of metallic spherical dome shells with thickness below 10 nm. PMID:24921317

Kumarasinghe, Chathurangi; Premaratne, Malin; Agrawal, Govind P

2014-05-19

323

Understanding boundary effects in quantum state tomography - One qubit case

NASA Astrophysics Data System (ADS)

For classical and quantum estimation with finite data sets, the estimation error can deviate significantly from its asymptotic (large data set) behavior. In quantum state tomography, a major reason for this is the existence of a boundary in the parameter space imposed by constraints, such as the positive semidefiniteness of density matrices. Intuitively, we should be able to reduce the estimation error by using our knowledge of these constraints. This intuition is correct for maximumlikelihood estimators, but the size of the reduction has not been evaluated quantitatively. In this proceeding, we evaluate the improvement in one qubit state tomography by using mathematical tools in classical statistical estimation theory. In particular, we show that the effect of the reduction decreases exponentially with respect to the number of data sets when the true state is mixed, and it remains at arbitrarily large data set when the true state is pure.

Sugiyama, Takanori; Turner, Peter S.; Murao, Mio

2014-12-01

324

Effects of Quantum Error Correction on Entanglement Sudden Death

We investigate the effects of error correction on non-local quantum coherence as a function of time, extending the study by Sainz and Bj\\"ork. We consider error correction of amplitude damping, pure phase damping and combinations of amplitude and phase damping as they affect both fidelity and quantum entanglement. Initial two-qubit entanglement is encoded in arbitrary real superpositions of both \\Phi-type and \\Psi-type Bell states. Our main focus is on the possibility of delay or prevention of ESD (early stage decoherence, or entanglement sudden death). We obtain the onset times for ESD as a function of the state-superposition mixing angle. Error correction affects entanglement and fidelity differently, and we exhibit initial entangled states for which error correction increases fidelity but decreases entanglement, and vice versa.

Muhammed Yönaç; J. H. Eberly

2012-11-24

325

NASA Astrophysics Data System (ADS)

The purpose of this thesis is to carry out a precise test of the standard model of particle physics, i.e., the model that describes the strong and electroweak interactions between quarks, leptons, and gauge bosons. Such a precision test may well lead to the discovery of new physics beyond the standard model. More specifically, this thesis gives a precise determination of |Vcb|, one of the parameters of the standard model which controls the semileptonic decay process B ? Dlnu. This parameter is one of several that make up the CKM matrix. If the standard model is correct, that matrix must be unitary. A deviation from unitarity would be a sign of new physics. Although this is mainly an electroweak process, it occurs in the environment of the strong interactions. The strong interaction effects are encoded in the form factor G , for the vector current transition from the B meson to the D meson. In this thesis, we calculate the form factor. Experimental measurements provide the product G |Vcb|. So theory and experiment together give |Vcb|. We calculate the form factor in a numerical simulation, using lattice quantum chromodynamics. Ours is the first numerical calculation of the full form factor (nonzero recoil) that takes into account all the effects of the strong interactions (including sea quarks) and carries out an extrapolation to physical quark masses in the limit of zero lattice spacing. We give the theoretical backgound of the calculation, describe our data analysis, give a detailed analysis of all sources of error, and fit our result and the experimental data from the Babar collaboration to get our final result, namely, |Vcb|=0.0402(20).

Qiu, Siwei

326

Loop quantum cosmology of Bianchi IX: Effective dynamics

We study numerically the solutions to the effective equations of Bianchi IX spacetimes within Loop Quantum Cosmology. We consider Bianchi IX models with and without inverse triad corrections whose matter content is a scalar field without mass. The solutions are classified using the classical observables. We show that both effective theories --with lapse N=V and N=1-- solve the big bang singularity and reproduce the classical dynamics far from the bounce. Moreover, due to the spatial compactness, there is an infinity number of bounces and recollapses. We study the limit of large volume and show that both effective theories reproduce the same dynamics, thus recovering general relativity. We implement a procedure to identify amongst the Bianchi IX solutions, those that behave like k=0,1 FLRW as well as Bianchi I, II, and VII_0 models. The effective solutions exhibit Bianchi I phases with Bianchi II transitions and also Bianchi VII_0 phases, which had not been studied before, at the quantum nor effective level. W...

Corichi, Alejandro

2015-01-01

327

A growing number of studies is being devoted to the identification of plausible quantum properties of spacetime which might give rise to observably large effects. The literature on this subject is now relatively large, including studies in string theory, loop quantum gravity and noncommutative geometry. It is useful to divide the various proposals into proposals involving a systematic quantum-gravity effect (an effect that would shift the main/average prediction for a given observable quantity) and proposals involving a non-systematic quantum-gravity effect (an effect that would introduce new fundamental uncertanties in some observable quantity). The case of quantum-gravity-induced particle-production-threshold anomalies, a much studied example of potentially observable quantum-gravity effect, is here used as an example to illustrate the differences to be expected between systematic and non-systematic effects.

Giovanni Amelino-Camelia; Y. Jack NG; Hendrik Van Dam

2002-04-24

328

Effective utilization of quantum-cascade distributed-feedback lasers in absorption spectroscopy

Effective utilization of quantum-cascade distributed-feedback lasers in absorption spectroscopy quantum-cascade lasers. This technique was combined with a 100-m path-length multipass cell and a zero.6320, 010.1280. 1. Introduction Recently developed quantum-cascade lasers1 have been demonstrated

329

Nonequilibrium phonon effects in midinfrared quantum cascade lasers Y. B. Shi and I. Knezevic

Nonequilibrium phonon effects in midinfrared quantum cascade lasers Y. B. Shi and I. Knezevic transport and output characteristics of terahertz quantum cascade lasers J. Appl. Phys. 103, 103113 (2008); 10.1063/1.2927469 Comparative analysis of resonant phonon THz quantum cascade lasers J. Appl. Phys

Knezevic, Irena

330

The effects of electron temperature in terahertz quantum cascade laser predictions

The effects of electron temperature in terahertz quantum cascade laser predictions Philip along with a description of the complete QCL prediction code. Keywords: quantum cascade lasers, terahertz, electron temperature, device modelling 1. INTRODUCTION A quantum cascade laser (QCL) is a type

Massachusetts at Lowell, University of

331

Quantum Interference Effects in Slowly Rotating NUT Space-time

General relativistic quantum interference effects in the slowly rotating NUT space-time as the Sagnac effect and the phase shift effect of interfering particle in neutron interferometer are considered. It was found that in the case of the Sagnac effect the influence of NUT parameter is becoming important due to the fact that the angular velocity of the locally non rotating observer must be larger than one in the Kerr space-time. In the case of neutron interferometry it is found that due to the presence of NUT-parameter an additional term in the phase shift of interfering particle emerges. This term can be, in principle, detected by sensitive interferometer and derived results can be further used in experiments to detect the gravitomagnetic charge. Finally, as an example, we apply the obtained results to the calculation of the UCN (ultra-cold neutrons) energy level modification in the slowly rotating NUT space-time.

V. S. Morozova; B. J. Ahmedov

2008-04-20

332

Temperature effects on quantum interference in molecular junctions

NASA Astrophysics Data System (ADS)

A number of experiments have demonstrated that destructive quantum interference (QI) effects in molecular junctions lead to very low conductances even at room temperature. On the other hand, another recent experiment showed increasing conductance with temperature which was attributed to decoherence effects destroying QI at finite temperatures. Here we study the influence of finite temperatures and electron-phonon interactions on QI in molecular junctions. Two different models leading to two inherently different types of QI effects are considered. Each model is exemplified by specific molecules and studied using first-principles calculations. We find that the molecules exhibiting QI show a much stronger temperature dependence of the conductance compared to molecules without QI. However, the large QI-induced suppression of the conductance remains, showing that QI effects are indeed robust against finite temperatures and inelastic scattering.

Markussen, Troels; Thygesen, Kristian S.

2014-02-01

333

Effect of quantum nuclear motion on hydrogen bonding

NASA Astrophysics Data System (ADS)

This work considers how the properties of hydrogen bonded complexes, X-H⋯Y, are modified by the quantum motion of the shared proton. Using a simple two-diabatic state model Hamiltonian, the analysis of the symmetric case, where the donor (X) and acceptor (Y) have the same proton affinity, is carried out. For quantitative comparisons, a parametrization specific to the O-H⋯O complexes is used. The vibrational energy levels of the one-dimensional ground state adiabatic potential of the model are used to make quantitative comparisons with a vast body of condensed phase data, spanning a donor-acceptor separation (R) range of about 2.4 - 3.0 Å, i.e., from strong to weak hydrogen bonds. The position of the proton (which determines the X-H bond length) and its longitudinal vibrational frequency, along with the isotope effects in both are described quantitatively. An analysis of the secondary geometric isotope effect, using a simple extension of the two-state model, yields an improved agreement of the predicted variation with R of frequency isotope effects. The role of bending modes is also considered: their quantum effects compete with those of the stretching mode for weak to moderate H-bond strengths. In spite of the economy in the parametrization of the model used, it offers key insights into the defining features of H-bonds, and semi-quantitatively captures several trends.

McKenzie, Ross H.; Bekker, Christiaan; Athokpam, Bijyalaxmi; Ramesh, Sai G.

2014-05-01

334

Effect of quantum nuclear motion on hydrogen bonding

This work considers how the properties of hydrogen bonded complexes, X–H?Y, are modified by the quantum motion of the shared proton. Using a simple two-diabatic state model Hamiltonian, the analysis of the symmetric case, where the donor (X) and acceptor (Y) have the same proton affinity, is carried out. For quantitative comparisons, a parametrization specific to the O–H?O complexes is used. The vibrational energy levels of the one-dimensional ground state adiabatic potential of the model are used to make quantitative comparisons with a vast body of condensed phase data, spanning a donor-acceptor separation (R) range of about 2.4 ? 3.0 Å, i.e., from strong to weak hydrogen bonds. The position of the proton (which determines the X–H bond length) and its longitudinal vibrational frequency, along with the isotope effects in both are described quantitatively. An analysis of the secondary geometric isotope effect, using a simple extension of the two-state model, yields an improved agreement of the predicted variation with R of frequency isotope effects. The role of bending modes is also considered: their quantum effects compete with those of the stretching mode for weak to moderate H-bond strengths. In spite of the economy in the parametrization of the model used, it offers key insights into the defining features of H-bonds, and semi-quantitatively captures several trends.

McKenzie, Ross H., E-mail: r.mckenzie@uq.edu.au; Bekker, Christiaan [School of Mathematics and Physics, University of Queensland, Brisbane 4072 (Australia)] [School of Mathematics and Physics, University of Queensland, Brisbane 4072 (Australia); Athokpam, Bijyalaxmi; Ramesh, Sai G. [Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560 012 (India)] [Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560 012 (India)

2014-05-07

335

The new vacuum-mode recoil separator MARA at JYFL

NASA Astrophysics Data System (ADS)

A new vacuum-mode recoil separator MARA (Mass Analysing Recoil Apparatus) is under design and construction at the Department of Physics in the University of Jyväskylä. The separator is intended to separate reaction products from the primary beam in mass region below A=150. The ion-optical configuration of the separator will be QQQD ED M, where a magnetic quadrupole (Q) triplet is followed by an electrostatic deflector (D E) and a magnetic dipole (D M). The total length of MARA will be less than 7.0 m and the first order resolving power more than 250 for a beam spot size of 2 mm. In this contribution the main properties of MARA are given and results from simulations are shown.

Sarén, J.; Uusitalo, J.; Leino, M.; Greenlees, P. T.; Jakobsson, U.; Jones, P.; Julin, R.; Juutinen, S.; Ketelhut, S.; Nyman, M.; Peura, P.; Rahkila, P.; Scholey, C.; Sorri, J.

2008-10-01

336

Doppler cooling to the recoil limit using sharp atomic transitions

In this paper, we develop an analytical approach to Doppler cooling of atoms by one- or two-photon transitions when the natural width of the excited level is so small that the process leads to a Doppler temperature comparable to the recoil temperature. A ``quenching'' of the sharp line is introduced in order to allow control of the time scale of the problem. In such limit, the usual Fokker-Planck equation does not correctly describe the cooling process. We propose a generalization of the Fokker-Planck equation and derive a new model which is able to reproduce correctly the numerical results, up to the recoil limit. Two cases of practical interest, one-photon Doppler cooling of strontium and two-photon Doppler cooling of hydrogen are considered.

V{é}ronique Zehnl{é}; Jean Claude Garreau

2002-07-23

337

The electromagnetic form factors of the nucleon characterize the effect of its internal structure on its response to an electromagnetic probe as studied in elastic electronnucleon scattering. These form factors are functions of the squared four-momentum transfer Q2 between the electron and the proton. The two main classes of observables of this reaction are the scattering cross section and polarization asymmetries, both of which are sensitive to the form factors in different ways. When considering large f momentum transfers, double-polarization observables offer superior sensitivity to the electric form factor. This thesis reports the results of a new measurement of the ratio of the electric and magnetic form factors of the proton at high momentum transfer using the recoil polarization technique. A polarized electron beam was scattered from a liquid hydrogen target, transferring polarization to the recoiling protons. These protons were detected in a magnetic spectrometer which was used to reconstruct their kinematics, including their scattering angles and momenta, and the position of the interaction vertex. A proton polarimeter measured the polarization of the recoiling protons by measuring the azimuthal asymmetry in the angular distribution of protons scattered in CH2 analyzers. The scattered electron was detected in a large acceptance electromagnetic calorimeter in order to suppress inelastic backgrounds. The measured ratio of the transverse and longitudinal polarization components of the scattered proton is directly proportional to the ratio of form factors GpE=GpM. The measurements reported in this thesis took place at Q2 =5.2, 6.7, and 8.5 GeV2, and represent the most accurate measurements of GpE in this Q2 region to date.

Andrew Puckett

2010-02-01

338

We introduce the quantum theoretical formulation to determine a posteriori, if existing, the quantum wave functions and to estimate the quantum interference effects of mental states. Such quantum features are actually found in the case of an experiment involving the perception and the cognition in humans. Also some specific psychological variables are introduced and it is obtained that they characterize in a stringent manner the quantum behaviour of mind during such performed experiment.

Elio Conte; Andrei Yuri Khrennikov; Orlando Todarello; Antonio Federici; Joseph P. Zbilut

2008-07-28

339

A time-asymmetric delta-kicked model for the quantum ratchet effect

NASA Astrophysics Data System (ADS)

We investigate a time-asymmetric delta-kicked model for the quantum ratchet effect, in which a flashing potential acts on a particle at unequal time intervals. Ratchet currents emerge when quantum resonances are excited. The currents in time-asymmetric models may be stronger than those found in the previous time-symmetric model. Our work expands upon the quantum delta-kicked model and may contribute to experimental investigation of the quantum transport of cold atoms.

Chen, Lei; Xiong, Chao; Xiao, Jin; Yuan, Hong-Chun

2014-12-01

340

Scintillation response of liquid xenon to low energy nuclear recoils

Liquid Xenon (LXe) is expected to be an excellent target and detection medium to search for dark matter in the form of Weakly Interacting Massive Particles (WIMPs). We have measured the scintillation efficiency of nuclear recoils with kinetic energy between 10.4 and 56.5 keV relative to that of 122 keV gamma rays from C57o. The scintillation yield of 56.5 keV

E. Aprile; K. L. Giboni; P. Majewski; K. Ni; M. Yamashita; R. Hasty; A. Manzur; D. N. McKinsey

2005-01-01

341

Ultra-shallow P + \\/N junctions formed by recoil implantation

The concept of recoil implantation is proposed to facilitate fabrication of ultrashallow p+\\/n junctions. In this method, a thin boron film is first deposited onto the Si wafer surface. Then the boron atoms are knocked\\u000a into the Si substrate by Ge implantation or Ar plasma source ion implantation. Dopant activation and damage removal are achieved\\u000a via rapid thermal annealing. Preliminary

Henley L. Liu; Steven S. Gearhart; John H. Booske; Wei Wang

1998-01-01

342

Recoiling Supermassive Black Holes: a search in the Nearby Universe

NASA Astrophysics Data System (ADS)

The coalescence of a binary black hole can be accompanied by a large gravitational recoil due to anisotropic emission of gravitational waves. A recoiling supermassive black hole (SBH) can subsequently undergo long-lived oscillations in the potential well of its host galaxy, suggesting that offset SBHs may be common in the cores of massive ellipticals. We have analyzed HST archival images of 14 nearby core ellipticals, finding evidence for small (<=10 pc) displacements between the AGN (locating the SBH) and the center of the galaxy (the mean photocenter) in 10 of them. Excluding objects that may be affected by large-scale isophotal asymmetries, we consider six galaxies to have detected displacements, including M87, where a displacement was previously reported by Batcheldor et al. 2010. In individual objects, these displacements can be attributed to residual gravitational recoil oscillations following a major or minor merger within the last few Gyr. For plausible merger rates, however, there is a high probability of larger displacements than those observed, if SBH coalescence took place in these galaxies. Remarkably, the AGN-photocenter displacements are approximately aligned with the radio source axis in four of the six galaxies with displacements, including three of the four having relatively powerful kpc-scale jets. This suggests intrinsic asymmetries in radio jet power as a possible displacement mechanism, although approximate alignments are also expected for gravitational recoil. Orbital motion in SBH binaries and interactions with massive perturbers can produce the observed displacement amplitudes but do not offer a ready explanation for the alignments.

Lena, Davide; Robinson, Andrew; Marconi, Alessandro; Axon, David; Capetti, Alessandro; Merritt, David; Batcheldor, Daniel

2015-01-01

343

One-logarithmic recoil correction in muonium hyperfine splitting

NASA Astrophysics Data System (ADS)

A source of recoil corrections to muonium hyperfine splitting which are linear in the logarithm of the electron-muon mass ratio is detected. The contribution is induced by the simultaneous insertion of muon and electron polarization loops in the external photon lines. This contribution is calculated analytically and is given by the numerical result ?E=(?2Z?/?)EF\\{0.6455[m/M]ln[M/m] +0.9212[m/M]\\}=0.011 37 kHz.

Li, G.; Samuel, Mark A.; Eides, Michael I.

1993-02-01

344

Ensemble Density Functional Approach to the Quantum Hall Effect

NASA Astrophysics Data System (ADS)

The fractional quantum Hall effect (FQHE) occurs in a two-dimensional electron gas of density n when a strong magnetic field perpendicular to the plane of the electron gas takes on certain strengths B(n). At these magnetic field strengths the system is incompressible, i.e., there is a finite cost in energy for creating charge density fluctuations in the bulk. Even so the boundary of the electron gas supports gapless modes of density waves. The bulk energy gap arises because of the strong electron-electron interactions. There are very good models for infinite homogeneous systems and for the gapless excitations of the boundary of the electron gas. But in order to explain experiments on quantum Hall systems, including Hall bars and quantum dots, new approaches are needed which can accurately describe inhomogeneous systems, including Landau level mixing and the spin degree of freedom. One possibility is an ensemble density functional theory approach that we have developed.(O. Heinonen, M.I. Lubin, and M.D. Johnson, Phys. Rev. Lett. 75), 4110 (1995)(O. Heinonen, M.I. Lubin, and M.D. Johnson, Int. J. Quant. Chem, December 1996) We have applied this to study edge reconstructions of spin-polarized quantum dots. The results for a six-electron test case are in excellent agreement with numerical diagonalizations. For larger systems, compressible and incompressible strips appear as the magnetic field is increased from the region in which a dot forms a compact so-called maximum density droplet. We have recently included spin degree of freedom to study the stability of a maximum density droplet, and charge-spin textures in inhomogeneous systems. As an example, when the Zeeman coupling is decreased, we find that the maximum density droplet develops a spin-structured edge instability. This implies that the spin degree of freedom may play a significant role in the study of edge modes at low or moderate magnetic fields.

Heinonen, O.

1997-03-01

345

Tunable interactions and the fractional quantum Hall effect

NASA Astrophysics Data System (ADS)

We explore several realistic methods of tuning the interactions in two-dimensional electronic systems in high magnetic fields. We argue that these experimental probes can be useful in studying the interplay of topology, quantum geometry and symmetry breaking in the fractional quantum Hall effect (FQHE). In particular, we show that the mixing of subbands and Landau levels in GaAs wide quantum wells breaks the particle-hole symmetry between the Moore-Read Pfaffian state and its particle-hole conjugate, the anti-Pfaffian, in such a way that the latter is unambiguously favored and generically describes the ground state at 5/2 filling [1]. Furthermore, the tilting of the magnetic field, or more generally variation of the band mass tensor, probes the fluctuation of the intrinsic metric degree of freedom of the incompressible fluids, and ultimately induces the crossover to the broken-symmetry and nematic phases in higher Landau levels [2]. Some of these mechanisms also lead to an enhancement of the excitation gap of the non-Abelian states, as observed in recent experiments. Finally, we compare the tuning capabilities in conventional systems with that in multilayer graphene and related materials with Dirac-type carriers where tuning the band structure and dielectric environment provides a simple and direct method to engineer more robust FQHE states and to study quantum transitions between them [3]. [4pt] [1] Z. Papic, F. D. M. Haldane, and E. H. Rezayi, arXiv:1209.6606 (2012).[0pt] [2] Bo Yang, Z. Papic, E. H. Rezayi, R. N. Bhatt, F. D. M. Haldane, Phys. Rev. B 85, 165318 (2012).[0pt] [3] Z. Papic, R. Thomale, D. A. Abanin, Phys. Rev. Lett. 107, 176602 (2011); Z. Papic, D. A. Abanin, Y. Barlas, and R. N. Bhatt, Phys. Rev. B 84, 241306(R) (2011); D. A. Abanin, Z. Papic, Y. Barlas, and R. N. Bhatt, New J. Phys. 14, 025009 (2012).

Papic, Zlatko

2013-03-01

346

Effect of exchange-correlation on quantum ion-acoustic soliton energy

NASA Astrophysics Data System (ADS)

The electrons exchange-correlation influence on the energy carried by the quantum ion-acoustic soliton (QIAS) is succinctly discussed. Starting from the one-dimensional quantum hydrodynamic model (in which the term of exchange-correlation for electrons is included), a deformed Korteweg-de Vries-like equation is derived. It is found that the QIAS energy experiences a depletion as a result of quantum diffraction. This quantum energy depletion may be counteracted by the exchange-correlation effect. The present work can be viewed as a first step towards the investigation of the exchange-correlation effects on the dynamics of solitary waves in quantum plasmas.

Mebrouk, Khireddine; Tribeche, Mouloud

2014-11-01

347

Determining influence of four-wave mixing effect on quantum key distribution

NASA Astrophysics Data System (ADS)

We consider the possibility of multiplexing the classical and quantum signals in a quantum cryptography system with optical fiber used as a transmission medium. If the quantum signal is located at a frequency close to the frequency of classical signals, a set of nonlinear effects such as FWM (four-wave mixing) and Raman scattering is observed. The impact of four-wave mixing (FWM) effect on error level is described and analyzed in this work in case of large frequency diversity between classical and quantum signals. It is shown that the influence of FWM is negligible for convenient quantum key distribution.

Vavulin, D. N.; Egorov, V. I.; Gleim, A. V.; Chivilikhin, S. A.

2014-10-01

348

Quantum confinement in Si and Ge nanostructures: effect of crystallinity

NASA Astrophysics Data System (ADS)

We look at the relationship between the preparation method of Si and Ge nanostructures (NSs) and the structural, electronic, and optical properties in terms of quantum confinement (QC). QC in NSs causes a blue shift of the gap energy with decreasing NS dimension. Directly measuring the effect of QC is complicated by additional parameters, such as stress, interface and defect states. In addition, differences in NS preparation lead to differences in the relevant parameter set. A relatively simple model of QC, using a `particle-in-a-box'-type perturbation to the effective mass theory, was applied to Si and Ge quantum wells, wires and dots across a variety of preparation methods. The choice of the model was made in order to distinguish contributions that are solely due to the effects of QC, where the only varied experimental parameter was the crystallinity. It was found that the hole becomes de-localized in the case of amorphous materials, which leads to stronger confinement effects. The origin of this result was partly attributed to differences in the effective mass between the amorphous and crystalline NS as well as between the electron and hole. Corrections to our QC model take into account a position dependent effective mass. This term includes an inverse length scale dependent on the displacement from the origin. Thus, when the deBroglie wavelength or the Bohr radius of the carriers is on the order of the dimension of the NS the carriers `feel' the confinement potential altering their effective mass. Furthermore, it was found that certain interface states (Si-O-Si) act to pin the hole state, thus reducing the oscillator strength.

Barbagiovanni, Eric G.; Lockwood, David J.; Costa Filho, Raimundo N.; Goncharova, Lyudmila V.; Simpson, Peter J.

2013-10-01

349

Fractional quantum Hall effect at Landau level filling ? =4 /11

NASA Astrophysics Data System (ADS)

We report low-temperature electronic transport results on the fractional quantum Hall effect of composite fermions at Landau level filling ? =4 /11 in a very high mobility and low density sample. Measurements were carried out at temperatures down to 15 mK , where an activated magnetoresistance Rx x and a quantized Hall resistance Rx y, within 1 % of the expected value of h /(4 /11 ) e2 , were observed. The temperature dependence of the Rx x minimum at 4 /11 yields an activation energy gap of ˜7 mK . Developing Hall plateaus were also observed at the neighboring states at ? =3 /8 and 5 /13 .

Pan, W.; Baldwin, K. W.; West, K. W.; Pfeiffer, L. N.; Tsui, D. C.

2015-01-01

350

Scalar spin chirality and quantum hall effect on triangular lattices

We study the Kondo Lattice and Hubbard models on a triangular lattice for band filling factor 3/4. We show that a simple non-coplanar chiral spin ordering (scalar spin chirality) is naturally realized in both models due to perfect nesting of the fermi surface. The resulting triple-Q magnetic ordering is a natural counterpart of the collinear Neel ordering of the half-filled square lattice Hubbard model. We show that the obtained chiral phase exhibits a spontaneous quantum Hall-effect with {sigma}{sub xy} = e{sup 2}/h.

Martin, Ivar [Los Alamos National Laboratory; Batista, Cristian D [Los Alamos National Laboratory

2008-01-01

351

Effects of dissipation on a quantum critical point with disorder.

We study the effects of dissipation on a disordered quantum phase transition with O(N) order-parameter symmetry by applying a strong-disorder renormalization group to the Landau-Ginzburg-Wilson field theory of the problem. We find that Ohmic dissipation results in a nonperturbative infinite-randomness critical point with unconventional activated dynamical scaling while super-Ohmic damping leads to conventional behavior. We discuss applications to the superconductor-metal transition in nanowires and to the Hertz theory of the itinerant antiferromagnetic transition. PMID:18233349

Hoyos, José A; Kotabage, Chetan; Vojta, Thomas

2007-12-01

352

One-dimensional model for the fractional quantum Hall effect

NASA Astrophysics Data System (ADS)

A simple one-dimensional model is proposed, in which N spinless repulsively interacting fermions occupy M>N degenerate states. It is argued that the energy spectrum and the wavefunctions of this system strongly resemble the spectrum and wavefunctions of 2D electrons in the lowest Landau level (the problem of the Fractional Quantum Hall Effect). In particular, Laughlin-type wavefunctions describe ground states at filling factors v = N/M = 1/q, q odd.. Within this model the complimentary wavefunction for v=1-1/q is found explicitly, and extremely simple ground state wavefunctions for arbitrary odd-denominator filling factors are proposed.

Dyakonov, M. I.

2013-08-01

353

Theory of the edge states in fractional quantum Hall effects

In this paper, the dynamical theory of the edge excitations of generic fractional quantum Hall (FQH) states is summarized and expanded. The low energy effective theory of the edge excitations for the most general abelian FQH states (including spin-unpolarized and multi-layer FQH states) and some non-abelian FQH states is derived using several different methods. The propagators of the electrons and the quasiparticles are calculated for the above FQH states. The microscopic theory of the edge excitations for the Laughlin states is also presented. Some simple applications of the edge theory to the transport properties of the FQH states are discussed.

Wen, X.G. (Massachusetts Inst. of Tech., Cambridge, MA (United States). Dept. of Physics)

1992-05-20

354

Interference Effects in the Conductance of Multilevel Quantum Dots

Using exact-diagonalization techniques supplemented by a Dyson equation embedding procedure, the transport properties of multilevel quantum dots are investigated in the Kondo regime. The conductance can be decomposed into the contributions of each level. It is shown that these channels can carry a different phase, and destructive interference processes are observed when the phase difference between them is {+-}{pi}. This effect is very different from those observed in bulk metals with magnetic impurities, where the phase differences play no significant role. The effect is also different from other recent studies of interference processes in dots, as discussed in the text. In particular, no external magnetic field is introduced here, and the dot-leads hopping amplitude for all levels are the same. However, conductance cancellations induced by interactions are still observed. Another interesting effect reported here is the formation of localized states that do not participate in the transport. When one of these states crosses the Fermi level, the electronic occupation of the quantum dot changes, modifying the many-body physics of the system and indirectly affecting the transport properties. Unusual discontinuities between two finite conductance values can occur as the gate voltage is varied, as discussed here.

Busser, Carlos A [ORNL; Martins, G. B. [Oakland University, Rochester, MI; Al Hassanieh, Khaled A [ORNL; Moreo, Adriana [ORNL; Dagotto, Elbio R [ORNL

2004-01-01

355

Disorder effects in the quantum Hall effect of graphene p-n junctions

NASA Astrophysics Data System (ADS)

The quantum Hall effect in graphene p-n junctions is studied numerically with emphasis on the effect of disorder at the interface of two adjacent regions. Conductance plateaus are found to be attached to the intensity of the disorder and are accompanied by universal conductance fluctuations in the bipolar regime, which is in good agreement with theoretical predictions of the random matrix theory on quantum chaotic cavities. The calculated Fano factors can be used in an experimental identification of the underlying transport character.

Li, Jian; Shen, Shun-Qing

2008-11-01

356

Ground-state cooling of a trapped ion by quantum interference pathways

NASA Astrophysics Data System (ADS)

We investigate the possibility of enhancement of cooling a trapped ion by combining the electromagnetically induced transparency (EIT) effect with the standing-wave coupling. Our study shows that the quantum destructive interference which is caused by the EIT effect and the standing-wave coupling can cancel all the dominant heating effects if appropriate parameters are chosen. The analytical predictions and numerical simulations show that the final temperature can be much lower than the recoil energy. In addition, this fast-cooling scheme is robust against fluctuations of the strength of the laser beams, which makes it more feasible for experimental realization.

Zhang, Shuo; Zhang, Jian-Qi; Duan, Qian-Heng; Guo, Chu; Wu, Chun-Wang; Wu, Wei; Chen, Ping-Xing

2014-10-01

357

Semianalytical quantum model for graphene field-effect transistors

NASA Astrophysics Data System (ADS)

We develop a semianalytical model for monolayer graphene field-effect transistors in the ballistic limit. Two types of devices are considered: in the first device, the source and drain regions are doped by charge transfer with Schottky contacts, while, in the second device, the source and drain regions are doped electrostatically by a back gate. The model captures two important effects that influence the operation of both devices: (i) the finite density of states in the source and drain regions, which limits the number of states available for transport and can be responsible for negative output differential resistance effects, and (ii) quantum tunneling across the potential steps at the source-channel and drain-channel interfaces. By comparison with a self-consistent non-equilibrium Green's function solver, we show that our model provides very accurate results for both types of devices, in the bias region of quasi-saturation as well as in that of negative differential resistance.

Pugnaghi, Claudio; Grassi, Roberto; Gnudi, Antonio; Di Lecce, Valerio; Gnani, Elena; Reggiani, Susanna; Baccarani, Giorgio

2014-09-01

358

By the use of various modes of Mössbauer spectroscopy after effects of irradiation of metal iron with (12)C(4+) and (14)N(5+) ions of medium energies, and alpha-particles and the (208)Tl, (208,212)Pb, and (216)Po recoil from a (228)Th-source have been studied. The experimental data obtained in the study enabled various types of external and internal radiation to be compared in regard to the damage they cause, as well as to their effect on the structure-, phase composition- and corrosion resistance properties of metallic iron. Irradiation with (12)C(4+) and (14)N(5+) ions is accompanied by both structural disordering of the ?-Fe lattice, and the appearance of ?-phase in the bulk metal. This is indicated by a single line which is 2 to 3-fold broadened (as compared to the lines of the magnetic sextet). This is a result of a strong local heating of the lattice in the thermal spike area with a subsequent instant cooling-down and recrystallization of this "molted" area. Irradiation of iron foils with (12)C(4+)- and (14)N(5+) ions and with recoil nuclei does provoke corrosion processes (the formation of ?-FeOOH) and is accompanied by an intensive oxidation of the metal. PMID:24378918

Alekseev, I; Novikov, D

2014-02-01

359

On Quantum Coherence Effects in Photo and Solar Cells

We show that quantum coherence can increase the quantum efficiency of various thermodynamic systems. For example, we can enhance the quantum efficiency for a quantum dot photocell, a laser based solar cell and the photo-Carnot quantum heat engine. Our results are fully consistent with the laws of thermodynamics contrary to comments found in the paper of A.P. Kirk, Phys. Rev. Lett. 106, 048703 (2011).

Kimberly Chapin; Konstantin Dorfman; Anatoly Svidzinsky; Marlan Scully

2011-02-01

360

Robustness of quantum spin Hall effect in an external magnetic field

NASA Astrophysics Data System (ADS)

The edge states in the quantum spin Hall effect are expected to be protected by time reversal symmetry. The experimental observation of the quantized conductance was reported in the InAs/GaSb quantum well (Du et al., arXiv:1306.1925), up to a large magnetic field, which raises a question on the robustness of the edge states in the quantum spin Hall effect under time reversal symmetry breaking. Here we present a theoretical calculation on topological invariants for the Benevig-Hughes-Zhang model in an external magnetic field, and find that the quantum spin Hall effect remains robust up to a large magnetic field. The critical value of the magnetic field breaking the quantum spin Hall effect is dominantly determined by the band gap at the ? point instead of the indirect band gap between the conduction and valence bands. This illustrates that the quantum spin Hall effect could persist even under time reversal symmetry breaking.

Zhang, Song-Bo; Zhang, Yan-Yang; Shen, Shun-Qing

2014-09-01

361

Quantum nuclear effects on the location of hydrogen above and below the palladium (100) surface

We report ab initio path integral molecular dynamics simulations of hydrogen and deuterium adsorbed on and absorbed in the Pd(100) surface at 100K. Significant quantum nuclear effects are found by comparing with conventional ab initio molecular dynamics simulations with classical nuclei. For on-surface adsorption, hydrogen resides higher above the surface when quantum nuclear effects are included, an effect which brings

Changjun Zhang; Angelos Michaelides

2011-01-01

362

NASA Technical Reports Server (NTRS)

Cosmic rays interact with extraterrestrial materials to produce a variety of spallation products. If these cosmogenic nuclides are produced within an inclusion in such material, then an important consideration is the loss of the product nuclei, which recoil out of the inclusion. Of course, at the same time, some atoms of the product nuclei under study may be knocked into the inclusion from the surrounding material, which is likely to have a different composition to that of the inclusion [1]. For example, Ne-21 would be produced in presolar grains, such as SiC, when irradiated in interstellar space. However, to calculate a presolar age, one needs to know how much 21Ne is retained in the grain. For small grains, the recoil losses might be large [2, 3] To study this effect under laboratory conditions, recoil measurements were made using protons with energies from 66 - 1600 MeV on Si, Al and Ba targets [3, 4, 5].

Sisterson, J. M.

2005-01-01

363

In this paper the electrical characteristics of metal oxide semiconductor (MOS) capacitors with high-k gate dielectric are investigated with quantum mechanical models. Both the self-consistent Schrödinger–Poisson (SP) model and the density gradient (DG) model are solved simultaneously to study quantum confinement effects (QCEs) for MOS capacitors. A computationally efficient parallel eigenvalue solution algorithm and a robust monotone iterative (MI) finite volume

Yiming Li; Jam-Wem Lee; Ting-Wei Tang; Tien-Sheng Chao; Tan-Fu Lei; S. M. Sze

2002-01-01

364

NASA Astrophysics Data System (ADS)

We consider the role of quantum effects in the transfer of hydrogen-like species in enzyme-catalyzed reactions. This review is stimulated by claims that the observed magnitude and temperature dependence of kinetic isotope effects (KIEs) implies that quantum tunneling below the energy barrier associated with the transition state significantly enhances the reaction rate in many enzymes. We review the path integral approach and the Caldeira-Leggett model, which provides a general framework to describe and understand tunneling in a quantum system that interacts with a noisy environment at nonzero temperature. Here the quantum system is the active site of the enzyme, and the environment is the surrounding protein and water. Tunneling well below the barrier only occurs for temperatures less than a temperature T0, which is determined by the curvature of the potential energy surface near the top of the barrier. We argue that for most enzymes this temperature is less than room temperature. We review typical values for the parameters in the Caldeira-Leggett Hamiltonian, including the frequency-dependent friction and noise due to the environment. For physically reasonable parameters, we show that quantum transition state theory gives a quantitative description of the temperature dependence and magnitude of KIEs for two classes of enzymes that have been claimed to exhibit signatures of quantum tunneling. The only quantum effects are those associated with the transition state, both reflection at the barrier top and tunneling just below the barrier. We establish that the friction and noise due to the environment are weak and only slightly modify the reaction rate. Furthermore, at room temperature and for typical energy barriers environmental fluctuations with frequencies much less than 1000 cm-1 do not have a significant effect on quantum corrections to the reaction rate. This is essentially because the time scales associated with the dynamics of proton transfer are faster than much of the low-frequency noise associated with the protein and solvent.

Bothma, Jacques P.; Gilmore, Joel B.; McKenzie, Ross H.

2010-05-01

365

Efficient Multi-Dimensional Simulation of Quantum Confinement Effects in Advanced MOS Devices

NASA Technical Reports Server (NTRS)

We investigate the density-gradient (DG) transport model for efficient multi-dimensional simulation of quantum confinement effects in advanced MOS devices. The formulation of the DG model is described as a quantum correction ot the classical drift-diffusion model. Quantum confinement effects are shown to be significant in sub-100nm MOSFETs. In thin-oxide MOS capacitors, quantum effects may reduce gate capacitance by 25% or more. As a result, the inclusion of quantum effects may reduce gate capacitance by 25% or more. As a result, the inclusion of quantum effects in simulations dramatically improves the match between C-V simulations and measurements for oxide thickness down to 2 nm. Significant quantum corrections also occur in the I-V characteristics of short-channel (30 to 100 nm) n-MOSFETs, with current drive reduced by up to 70%. This effect is shown to result from reduced inversion charge due to quantum confinement of electrons in the channel. Also, subthreshold slope is degraded by 15 to 20 mV/decade with the inclusion of quantum effects via the density-gradient model, and short channel effects (in particular, drain-induced barrier lowering) are noticeably increased.

Biegel, Bryan A.; Ancona, Mario G.; Rafferty, Conor S.; Yu, Zhiping

2000-01-01

366

Biexcitonic cavity quantum electrodynamics effect on nonlinear spectra of a quantum dot

NASA Astrophysics Data System (ADS)

We theoretically study cross-polarized pump-probe spectra of a quantum dot (QD) embedded in a microcavity in the cavity quantum electrodynamics treatment. Recently, observations of a vacuum Rabi splitting for a QD in microcavity have been reported. The vacuum Rabi splitting is the level separation of one-excitation dressed states (1e states). However, two-excitation dressed states (2e states) have not been observed in this system. We discuss the possibility to observe pump-probe signal coming from the cross-polarized 2e states, in which the energy levels of a QD are modeled by a four-level system consisting of the ground state, right- and left-polarized excitons, and a biexciton. The signal peaks due to the cross-polarized 2e states are found when the quality factor of the cavity is extremely large. The spectral intensity is dramatically enhanced due to the cavity effect. The enhancement rate is independent of the coupling constants between the exciton (biexciton) and a cavity photon when a well-defined vacuum Rabi splitting is formed. However, a strong suppression of the signal occurs at a condition where the energy of the 1e state coincides with the energy difference between 1e and cross-polarized 2e states.

Ajiki, Hiroshi; Ishihara, Hajime

2008-12-01

367

Quantum resonance effects in exchange, photodissociation, and recombination reactions

This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). This project studied quantum resonance effects on chemical reactions. The authors accurate reactive scattering calculations showed that quantum resonance phenomena dominate most chemical reactions and are essential to any real understanding of reactivity. It was found that, as long-lived metastable states of the colliding system, resonances can decay to reactants, products, or a mixture of both. Only the latter contribute to reaction. Conditions under which resonances can be neglected or treated statistically were studied. Important implications about the mechanism of recombination reactions were discovered, and some remarkable effects of geometric phases on the symmetries and energies of resonances were also discovered. Calculations were completed for the reaction H + O{sub 2} {yields} OH + O, which is the rate limiting step in the combustion of all hydrocarbons and the single most important reaction in all of combustion chemistry.

Pack, R.; Kendrick, B.; Kress, J.; Walker, R. [Los Alamos National Lab., NM (United States); Hayes, E. [Ohio State Univ., Columbus, OH (United States); Lagana, A. [Univ. of Perugia (Italy); Parker, G. [Univ. of Oklahoma, Norman, OK (United States); Butcher, E. [Auburn Univ., AL (United States)

1996-04-01

368

Testing quantum-like models of judgment for question order effects

Lately, so-called "quantum" models, based on parts of the mathematics of quantum mechanics, have been developed in decision theory and cognitive sciences to account for seemingly irrational or paradoxical human judgments. In this paper, we limit ourselves to such quantum-like models that address order effects. It has been argued that such models are able to account for existing and new empirical data, and meet some a priori predictions. From the quantum law of reciprocity, we derive new empirical predictions that we call the Grand Reciprocity equations, that must be satisfied by quantum-like models on the condition that they are non-degenerate. We show that existing non-degenerate quantum-like models for order effects fail this test on several existing data sets. We take it to suggest that degenerate quantum-like models should be the focus of forthcoming research in the area.

Thomas Boyer-Kassem; Sébastien Duchêne; Éric Guerci

2015-01-19

369

The trouble with orbits: the Stark effect in the old and the new quantum theory

The old quantum theory and Schr\\"odinger's wave mechanics (and other forms of quantum mechanics) give the same results for the line splittings in the first-order Stark effect in hydrogen, the leading terms in the splitting of the spectral lines emitted by a hydrogen atom in an external electric field. We examine the account of the effect in the old quantum theory, which was hailed as a major success of that theory, from the point of view of wave mechanics. First, we show how the new quantum mechanics solves a fundamental problem one runs into in the old quantum theory with the Stark effect. It turns out that, even without an external field, it depends on the coordinates in which the quantum conditions are imposed which electron orbits are allowed in a hydrogen atom. The allowed energy levels and hence the line splittings are independent of the coordinates used but the size and eccentricity of the orbits are not. In the new quantum theory, this worrisome non-uniqueness of orbits turns into the perfectly innocuous non-uniqueness of bases in Hilbert space. Second, we review how the so-called WKB (Wentzel-Kramers-Brillouin) approximation method for solving the Schr\\"odinger equation reproduces the quantum conditions of the old quantum theory amended by some additional half-integer terms. These extra terms remove the need for some arbitrary extra restrictions on the allowed orbits that the old quantum theory required over and above the basic quantum conditions

Anthony Duncan; Michel Janssen

2014-04-21

370

Thermoelectric effects in quantum Hall systems beyond linear response

NASA Astrophysics Data System (ADS)

We consider a quantum Hall system with an antidot acting as a energy dependent scatterer. In the purely charge case, we find deviations from the Wiedemann-Franz law that take place in the nonlinear regime of transport. We also discuss Peltier effects beyond linear response and describe both effects using magnetic-field asymmetric transport coefficients. For the spin case such as that arising along the helical edge states of a two-dimensional topological insulator, we investigate the generation of spin currents as a result of applied voltage and temperature differences in samples attached to ferromagnetic leads. We find that in the parallel configuration the spin current can be tuned with the leads' polarization even in the linear regime of transport. In contrast, for antiparallel magnetizations the spin currents has a strict nonlinear dependence on the the applied fields.

López, Rosa; Hwang, Sun-Yong; Sánchez, David

2014-12-01

371

Anisotropic charge kondo effect in a triple quantum dot.

We predict that an anisotropic charge Kondo effect appears in a triple quantum dot, when the system has twofold degenerate ground states of (1,1,0) and (0,0,1) charge configurations. Using bosonization and refermionization methods, we find that at low temperature the system has the two different phases of massive charge fluctuations between the two charge configurations and vanishing fluctuations, which are equivalent with the Kondo-screened and ferromagnetic phases of the anisotropic Kondo model, respectively. The phase transition is identifiable by electron conductance measurement, offering the possibility of experimentally exploring the anisotropic Kondo model. Our charge Kondo effect has a similar origin to that in a negative-U Anderson impurity. PMID:25526143

Yoo, Gwangsu; Park, Jinhong; Lee, S-S B; Sim, H-S

2014-12-01

372

Anisotropic Charge Kondo Effect in a Triple Quantum Dot

NASA Astrophysics Data System (ADS)

We predict that an anisotropic charge Kondo effect appears in a triple quantum dot, when the system has twofold degenerate ground states of (1,1,0) and (0,0,1) charge configurations. Using bosonization and refermionization methods, we find that at low temperature the system has the two different phases of massive charge fluctuations between the two charge configurations and vanishing fluctuations, which are equivalent with the Kondo-screened and ferromagnetic phases of the anisotropic Kondo model, respectively. The phase transition is identifiable by electron conductance measurement, offering the possibility of experimentally exploring the anisotropic Kondo model. Our charge Kondo effect has a similar origin to that in a negative-U Anderson impurity.

Yoo, Gwangsu; Park, Jinhong; Lee, S.-S. B.; Sim, H.-S.

2014-12-01

373

Barrier penetration effects on thermopower in semiconductor quantum wells

Finite confinement effects, due to the penetration of the electron wavefunction into the barriers of a square well potential, on the low–temperature acoustic-phonon-limited thermopower (TP) of 2DEG are investigated. The 2DEG is considered to be scattered by acoustic phonons via screened deformation potential and piezoelectric couplings. Incorporating the barrier penetration effects, the dependences of diffusion TP and phonon drag TP on barrier height are studied. An expression for phonon drag TP is obtained. Numerical calculations of temperature dependences of mobility and TP for a 10 nm InN/In {sub x}Ga{sub 1?x}N quantum well for different values of x show that the magnitude and behavior of TP are altered. A decrease in the barrier height from 500 meV by a factor of 5, enhances the mobility by 34% and reduces the TP by 58% at 20 K. Results are compared with those of infinite barrier approximation.

Vaidya, R. G. [Department of Physics, Karnatak University, Dharwad, Karnataka, India – 580 003 (India) [Department of Physics, Karnatak University, Dharwad, Karnataka, India – 580 003 (India); Department of Physics and C.E.I.E, Tumkur University, Tumkur, Karnataka, India – 573 102 (India); Sankeshwar, N. S., E-mail: n-s-sankeshwar@hotmail.com; Mulimani, B. G. [Department of Physics, Karnatak University, Dharwad, Karnataka, India – 580 003 (India)] [Department of Physics, Karnatak University, Dharwad, Karnataka, India – 580 003 (India)

2014-01-15

374

NASA Astrophysics Data System (ADS)

InGaN/GaN light-emitting diodes (LEDs) grown along the polar orientations significantly suffer from the quantum confined Stark effect (QCSE) caused by the strong polarization induced electric field in the quantum wells, which is a fundamental problem intrinsic to the III-nitrides. Here, we show that the QCSE is self-screened by the polarization induced bulk charges enabled by designing quantum barriers. The InN composition of the InGaN quantum barrier graded along the growth orientation opportunely generates the polarization induced bulk charges in the quantum barrier, which well compensate the polarization induced interface charges, thus avoiding the electric field in the quantum wells. Consequently, the optical output power and the external quantum efficiency are substantially improved for the LEDs. The ability to self-screen the QCSE using polarization induced bulk charges opens up new possibilities for device engineering of III-nitrides not only in LEDs but also in other optoelectronic devices.

Zhang, Zi-Hui; Liu, Wei; Ju, Zhengang; Tiam Tan, Swee; Ji, Yun; Kyaw, Zabu; Zhang, Xueliang; Wang, Liancheng; Wei Sun, Xiao; Volkan Demir, Hilmi

2014-06-01

375

InGaN/GaN light-emitting diodes (LEDs) grown along the polar orientations significantly suffer from the quantum confined Stark effect (QCSE) caused by the strong polarization induced electric field in the quantum wells, which is a fundamental problem intrinsic to the III-nitrides. Here, we show that the QCSE is self-screened by the polarization induced bulk charges enabled by designing quantum barriers. The InN composition of the InGaN quantum barrier graded along the growth orientation opportunely generates the polarization induced bulk charges in the quantum barrier, which well compensate the polarization induced interface charges, thus avoiding the electric field in the quantum wells. Consequently, the optical output power and the external quantum efficiency are substantially improved for the LEDs. The ability to self-screen the QCSE using polarization induced bulk charges opens up new possibilities for device engineering of III-nitrides not only in LEDs but also in other optoelectronic devices.

Zhang, Zi-Hui; Liu, Wei; Ju, Zhengang; Tiam Tan, Swee; Ji, Yun; Kyaw, Zabu; Zhang, Xueliang; Wang, Liancheng; Wei Sun, Xiao, E-mail: exwsun@ntu.edu.sg, E-mail: volkan@stanfordalumni.org [LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Volkan Demir, Hilmi, E-mail: exwsun@ntu.edu.sg, E-mail: volkan@stanfordalumni.org [LUMINOUS Centre of Excellence for Semiconductor Lighting and Displays, School of Electrical and Electronic Engineering, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Department of Electrical and Electronics, Department of Physics, and UNAM-Institute of Material Science and Nanotechnology, Bilkent University, TR-06800 Ankara (Turkey)

2014-06-16

376

Gravitational Wave Recoil and the Retention of Intermediate Mass Black Holes

During the inspiral and merger of a binary black hole, gravitational radiation is emitted anisotropically due to asymmetries in the merger configuration. This anisotropic radiation leads to a gravitational wave kick, or recoil velocity, as large as ~ 4000 km/sec. We investigate the effect gravitational recoil has on the retention of intermediate mass black holes (IMBH) within Galactic globular clusters. Assuming that our current understanding of IMBH-formation is correct and yields an IMBH-seed in every globular cluster, we find a significant problem retaining low mass IMBHs (1000 $\\Msun$) in the typical merger-rich globular cluster environment. Given a uniform black hole spin distribution and orientation and a Kroupa IMF, we find that at most 3% of the globular clusters can retain an IMBH larger than 1000 $\\Msun$ today. For a population of black holes that better approximates mass loss from winds and supernovae, we find that 16% of globulars can retain an IMBH larger than 1000 $\\Msun$. Our calculations show that if there are black holes of mass $M > 60 \\Msun$ in a cluster, repeated IMBH-BH encounters will eventually eject a 1000 $\\Msun$ IMBH with greater than 30% probability. As a consequence, a large population of rogue black holes may exist in our Milky Way halo. We discuss the dynamical implications of this subpopulation, and its possible connection to ultraluminous X-ray sources (ULXs).

Kelly Holley-Bockelmann; Kayhan Gultekin; Deirdre Shoemaker; Nico Yunes

2007-07-09

377

Excition states in semiconductor quantum dots in the modified effective mass approximation

A new modified effective mass approximation is suggested to describe the excitonic energy spectrum of quantum dots of radii a comparable to the exciton Bohr radius a{sub ex}{sup 0}. It is shown that, for quantum dots simulated by infinitely deep potential wells, the effective mass approximation is appropriate for describing excitons in quantum dots of radii a {approx} a{sub ex}{sup 0}, if the reduced effective mass of the excitons, {mu}, is considered as a function of the radius of the quantum dot a, {mu} = {mu}(a)

Pokutnyi, S. I. [National Academy of Sciences of Ukraine, Kurdyumov Institute of the Physics of Metals (Ukraine)], E-mail: Pokutnyi_Sergey@inbox.ru

2007-11-15

378

Fractional Quantum Hall Effect and Wigner Crystal of Interacting Composite Fermions

NASA Astrophysics Data System (ADS)

In two-dimensional electron systems confined to GaAs quantum wells, as a function of either tilting the sample in a magnetic field or increasing density, we observe multiple spin-polarization transitions of the fractional quantum Hall states at filling factors ? =4 /5 and 5 /7 . The number of observed transitions provides evidence that these are fractional quantum Hall states of interacting two-flux composite fermions. Moreover, the fact that the reentrant integer quantum Hall effect near ? =4 /5 always develops following the transition to full spin polarization of the ? =4 /5 fractional quantum Hall state links the reentrant phase to a pinned ferromagnetic Wigner crystal of composite fermions.

Liu, Yang; Kamburov, D.; Hasdemir, S.; Shayegan, M.; Pfeiffer, L. N.; West, K. W.; Baldwin, K. W.

2014-12-01

379

Phase diagram of the two-component fractional quantum Hall effect.

We calculate the phase diagram of the two component fractional quantum Hall effect as a function of the spin or valley Zeeman energy and the filling factor, which reveals new phase transitions and phase boundaries spanning many fractional plateaus. This phase diagram is relevant to the fractional quantum Hall effect in graphene and in GaAs and AlAs quantum wells, when either the spin or valley degree of freedom is active. PMID:25165951

Archer, Alexander C; Jain, Jainendra K

2013-06-14

380

Fractional quantum Hall effect in higher Landau levels

NASA Astrophysics Data System (ADS)

The fractional quantum Hall effect in the second Landau level (LL), particularly at filling factor 5/2, has seen a resurgence of research activity since its possible use in fault tolerant topological quantum computation was pointed out[1]. We do not, however, have a complete understanding of the FQHE in the second LL(SLL) compared with the corresponding lowest LL situation. For instance, while the Moore-Read Pfaffian state is the leading candidate for the 5/2 FQHE, it has only a moderate overlap (˜0.9) with the exact wavefunction for finite size systems of electrons interacting through the Coulomb interaction. In this work we consider the finite thickness of the electrically polarized quasi-2D quantum confinement in three models: Zhang-Das Sarma, infinite square-well, and Fang-Howard potentials, respectively. We calculate overlap between the Laughlin(fillings 1/3 and 1/5) or Pfaffian(filling 1/2) and the corresponding exact state, obtained by exact diagonalization, in the lowest, second, and third LLs as a function of the layer thickness. We find that the Pfaffian state becomes a nearly exact description of the physics at filling factor 1/2 in the SLL for a finite value of thickness. We also show the comparative trends in the ground state energy and the excitation gap as a function of layer thickness, comparing among the first, second, and the third LLs. We acknowledge support from Microsoft Q Project. [1] Das Sarma et al. PRL 94, 166802(2005)

Peterson, Michael R.; Das Sarma, S.

2008-03-01

381

Landau damping and the onset of particle trapping in quantum plasmas

Using analytical theory and simulations, we assess the impact of quantum effects on non-linear wave-particle interactions in quantum plasmas. We more specifically focus on the resonant interaction between Langmuir waves and electrons, which, in classical plasmas, lead to particle trapping. Two regimes are identified depending on the difference between the time scale of oscillation t{sub B}(k)=?(m/eEk) of a trapped electron and the quantum time scale t{sub q}(k)=2m/?k{sup 2} related to recoil effect, where E and k are the wave amplitude and wave vector. In the classical-like regime, t{sub B}(k)?quantum regime, t{sub B}(k)?>?t{sub q}(k), particle trapping is hampered by the finite recoil imparted to resonant electrons in their interactions with plasmons.

Daligault, Jérôme [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2014-04-15

382

We evaluate the interband optical absorption of a semiconductor quantum well in the presence of a uniform electric field perpendicular to the layer and neglecting excitonic effects. We show that this formally becomes the Franz-Keldysh effect in the limit of an infinitely thick layer. When the potential drop across the layer is small compared to the confinement energy we obtain

D. A. B. Miller; D. S. Chemla; S. Schmitt-Rink

1986-01-01

383

Recoil ion charge state distribution following the beta(sup +) decay of {sup 21}Na

The charge state distribution following the positron decay of 21Na has been measured, with a larger than expected fraction of the daughter 21Ne in positive charge states. No dependence on either the positron or recoil nucleus energy is observed. The data is compared to a simple model based on the sudden approximation. Calculations suggest a small but important contribution from recoil ionization has important consequences for precision beta decay correlation experiments detecting recoil ions.

Scielzo, Nicholas D.; Freedman, Stuart J.; Fujikawa, Brian K.; Vetter, Paul A.

2003-01-03

384

Nuclear recoil detection in liquid argon using a two-phase CRAD and DD neutron generator

NASA Astrophysics Data System (ADS)

The detection of nuclear recoils in noble liquids using neutron elastic scattering off nuclei is relevant in the field of calibration of rare-event detectors for dark matter search and coherent neutrino-nucleus scattering experiments. We present here the first results on nuclear recoil detection in liquid Ar, using a two-phase Cryogenic Avalanche Detector (CRAD) and DD neutron generator. The technique to select the nuclear recoils for backward neutron scattering has been demonstrated.

Bondar, A.; Buzulutskov, A.; Dolgov, A.; Grishnyaev, E.; Polosatkin, S.; Shemyakina, E.; Sokolov, A.

2014-08-01

385

Quantum Effects in the Diffusion of Hydrogen on Ru(0001).

An understanding of hydrogen diffusion on metal surfaces is important not only for its role in heterogeneous catalysis and hydrogen fuel cell technology but also because it provides model systems where tunneling can be studied under well-defined conditions. Here we report helium spin-echo measurements of the atomic-scale motion of hydrogen on the Ru(0001) surface between 75 and 250 K. Quantum effects are evident at temperatures as high as 200 K, while below 120 K we observe a tunneling-dominated temperature-independent jump rate of 1.9 × 10(9) s(-1), many orders of magnitude faster than previously seen. Quantum transition-state theory calculations based on ab initio path-integral simulations reproduce the temperature dependence of the rate at higher temperatures and predict a crossover to tunneling-dominated diffusion at low temperatures. However, the tunneling rate is underestimated, highlighting the need for future experimental and theoretical studies of hydrogen diffusion on this and other well-defined surfaces. PMID:24920996

McIntosh, Eliza M; Wikfeldt, K Thor; Ellis, John; Michaelides, Angelos; Allison, William

2013-05-01

386

Band Collapse and the Quantum Hall Effect in Graphene

The recent Quantum Hall experiments in graphene have confirmed the theoretically well-understood picture of the quantum Hall (QH) conductance in fermion systems with continuum Dirac spectrum. In this paper we take into account the lattice, and perform an exact diagonalization of the Landau problem on the hexagonal lattice. At very large magnetic fields the Dirac argument fails completely and the Hall conductance, given by the number of edge states present in the gaps of the spectrum, is dominated by lattice effects. As the field is lowered, the experimentally observed situation is recovered through a phenomenon which we call band collapse. As a corollary, for low magnetic field, graphene will exhibit two qualitatively different QHE's: at low filling, the QHE will be dominated by the 'relativistic' Dirac spectrum and the Hall conductance will be odd-integer; above a certain filling, the QHE will be dominated by a non-relativistic spectrum, and the Hall conductance will span all integers, even and odd.

Bernevig, B.Andrei; Hughes, Taylor L.; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.; Chen, Han-Dong; /Illinois U., Urbana; Wu, Congjun; /Santa Barbara, KITP

2010-03-16

387

Electronic transport and quantum localization effects in organic semiconductors

NASA Astrophysics Data System (ADS)

We explore the charge transport mechanism in organic semiconductors based on a model that accounts for the thermal intermolecular disorder at work in pure crystalline compounds, as well as extrinsic sources of disorder that are present in current experimental devices. Starting from the Kubo formula, we describe a theoretical framework that relates the time-dependent quantum dynamics of electrons to the frequency-dependent conductivity. The electron mobility is then calculated through a relaxation time approximation that accounts for quantum localization corrections beyond Boltzmann theory, and allows us to efficiently address the interplay between highly conducting states in the band range and localized states induced by disorder in the band tails. The emergence of a “transient localization” phenomenon is shown to be a general feature of organic semiconductors that is compatible with the bandlike temperature dependence of the mobility observed in pure compounds. Carrier trapping by extrinsic disorder causes a crossover to a thermally activated behavior at low temperature, which is progressively suppressed upon increasing the carrier concentration, as is commonly observed in organic field-effect transistors. Our results establish a direct connection between the localization of the electronic states and their conductive properties, formalizing phenomenological considerations that are commonly used in the literature.

Ciuchi, S.; Fratini, S.

2012-12-01

388

Nanoscale optimization of quantum dot media for effective photovoltaic conversion

NASA Astrophysics Data System (ADS)

Nanoscale engineering of band profile and potential profile provide effective tools for the management of photoelectron processes in quantum dot (QD) photovoltaic devices. We investigate the QD devices with various 1-?m InAs /GaAs QD media placed in a 3-?m base GaAs p-n junction. We found that n-charging of quantum dots (QDs) create potential barriers around QDs. QD growth between ultrathin AlGaAs layers leads to the formation of AlGaAs "fence" barriers, and reduces the wetting layers (WLs). The barriers around QDs and reduction of the wetting layer substantially suppress recombination processes via QDs. The n-doping of interdot space in QD media enhances electron extraction from QDs. All of our QD devices show short-circuit current, JSC, higher than that of the reference cell, but smaller open-circuit voltage, VOC.. In the QD devices, the short circuit currents increase by ~0.1 mA/cm2 per dot layer. JSC reaches 28.4 mA/cm2 in the device with QD media that combines dot charging, fence barriers, and WL reduction.

Sablon, K. A.; Sergeev, A.; Little, J. W.; Vagidov, N.; Mitin, V.

2014-06-01

389

Loop Quantum effects on Om-diagnostic and its Cosmological Implications

In this paper we study the Loop quantum effects on the \\textit{Om} diagnostic and subsequently on the universe. We reconstruct the \\textit{Om} diagnostic in the background of Loop quantum gravity and then study the behaviour of various Chaplygin gas dark energy models using the modified diagnostic in a comparative scenario. The trajectories discriminate the various dark energy models from each other both in the Einstein gravity as well as Loop quantum gravity. The Loop quantum effects are also clearly noticeable from the trajectories in past, present and future universe. We see that the Loop quantum deviations are highly pronounced in the early universe, but alleviates as we tend towards the present universe and continue to decay in future. Thus it puts a big question on the effectiveness and consequently the suitability of loop quantum cosmology to explain the future universe.

Rudra, Prabir

2014-01-01

390

Loop Quantum effects on Om-diagnostic and its Cosmological Implications

In this paper we study the Loop quantum effects on the \\textit{Om} diagnostic and subsequently on the universe. We reconstruct the \\textit{Om} diagnostic in the background of Loop quantum gravity and then study the behaviour of various Chaplygin gas dark energy models using the modified diagnostic in a comparative scenario. The trajectories discriminate the various dark energy models from each other both in the Einstein gravity as well as Loop quantum gravity. The Loop quantum effects are also clearly noticeable from the trajectories in past, present and future universe. We see that the Loop quantum deviations are highly pronounced in the early universe, but alleviates as we tend towards the present universe and continue to decay in future. Thus it puts a big question on the effectiveness and consequently the suitability of loop quantum cosmology to explain the future universe.

Prabir Rudra

2014-10-19

391

Waves in a bounded quantum plasma with electron exchange-correlation effects

Within a quantum hydrodynamic model, the collective excitations of the quantum plasma with electron exchange-correlation effects in a nano-cylindrical wave guide are studied both analytically and numerically. The influences of the electron exchange-correlation potential, the radius of the wave guide, and the quantum effect on the dispersion properties of the bounded quantum plasma are discussed. Significant frequency-shift induced by the electron exchange-correlation effect, the radius of the wave guide and the quantum correction are observed. It is found that the influence of the electron exchange-correlation, the radius of the wave guide and the quantum correction on the wave modes in a bounded nano-waveguide are strongly coupled.

Ma Yutng; Mao Shenghng; Xue Juji [Key Laboratory of Atomic and Molecular Physics and Functional Materials of Gansu Province, College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China)

2011-10-15

392

Effects of Landau level mixing on the fractional quantum Hall effect in monolayer graphene.

We report results of exact diagonalization studies of the spin- and valley-polarized fractional quantum Hall effect in the N = 0 and N = 1 Landau levels in graphene. We use an effective model that incorporates Landau level mixing to lowest order in the parameter ? = ((e(2)/??)/(?v(F)/?)) = (e(2)/?v(F)?), which is magnetic field independent and can only be varied through the choice of substrate. We find Landau level mixing effects are negligible in the N = 0 Landau level for ? ? 2. In fact, the lowest Landau level projected Coulomb Hamiltonian is a better approximation to the real Hamiltonian for graphene than it is for semiconductor based quantum wells. Consequently, the principal fractional quantum Hall states are expected in the N = 0 Landau level over this range of ?. In the N = 1 Landau level, fractional quantum Hall states are expected for a smaller range of ? and Landau level mixing strongly breaks particle-hole symmetry, producing qualitatively different results compared to the N = 0 Landau level. At half filling of the N = 1 Landau level, we predict the anti-Pfaffian state will occur for ? ? 0.25-0.75. PMID:25192110

Peterson, Michael R; Nayak, Chetan

2014-08-22

393

(7)Be-recoil radiolabelling of industrially manufactured silica nanoparticles.

Radiolabelling of industrially manufactured nanoparticles is useful for nanoparticle dosimetry in biodistribution or cellular uptake studies for hazard and risk assessment. Ideally for such purposes, any chemical processing post production should be avoided as it may change the physico-chemical characteristics of the industrially manufactured species. In many cases, proton irradiation of nanoparticles allows radiolabelling by transmutation of a tiny fraction of their constituent atoms into radionuclides. However, not all types of nanoparticles offer nuclear reactions leading to radionuclides with adequate radiotracer properties. We describe here a process whereby in such cases nanoparticles can be labelled with (7)Be, which exhibits a physical half-life of 53.29 days and emits ?-rays of 478 keV energy, and is suitable for most radiotracer studies. (7)Be is produced via the proton-induced nuclear reaction (7)Li(p,n)(7)Be in a fine-grained lithium compound with which the nanoparticles are mixed. The high recoil energy of (7)Be atoms gives them a range that allows the (7)Be-recoils to be transferred from the lithium compound into the nanoparticles by recoil implantation. The nanoparticles can be recovered from the mixture by dissolving the lithium compound and subsequent filtration or centrifugation. The method has been applied to radiolabel industrially manufactured SiO2 nanoparticles. The process can be controlled in such a way that no alterations of the (7)Be-labelled nanoparticles are detectable by dynamic light scattering, X-ray diffraction and electron microscopy. Moreover, cyclotrons with maximum proton energies of 17-18 MeV that are available in most medical research centres could be used for this purpose. PMID:25285032

Holzwarth, Uwe; Bellido, Elena; Dalmiglio, Matteo; Kozempel, Jan; Cotogno, Giulio; Gibson, Neil

2014-01-01

394

2005 Nature Publishing Group Strong quantum-confined Stark effect in germanium

Â© 2005 Nature Publishing Group Strong quantum-confined Stark effect in germanium quantum to integrate with silicon electronic devices. Germanium is routinely integrated with silicon in electronics8 , but previous siliconÂgermanium structures have also not shown strong modulation effects9Â13 . Here we report

Miller, David A. B.

395

Unconventional quantum Hall effect and Berry's phase of 2pi in bilayer graphene

There are two known distinct types of the integer quantum Hall effect. One is the conventional quantum Hall effect, characteristic of two-dimensional semiconductor systems, and the other is its relativistic counterpart observed in graphene, where charge carriers mimic Dirac fermions characterized by Berry's phase pi, which results in shifted positions of the Hall plateaus. Here we report a third type

K. S. Novoselov; E. McCann; S. V. Morozov; V. I. Fal'Ko; M. I. Katsnelson; U. Zeitler; D. Jiang; F. Schedin; A. K. Geim

2006-01-01

396

MAS 335 Cryptography Notes 12: Quantum effects and bibliography Spring 2006

MAS 335 Cryptography Notes 12: Quantum effects and bibliography Spring 2006 Quantum effects systems, and how this behaviour is relevant to cryptography. There are two aspects which we treat in turn solve the hard problems on which modern public-key cryptography depends (factorisation and dis- crete

Banaji,. Murad

397

In the frame of the variational method and the effective-mass approximation, the effects of hydrostatic pressure and temperature on the binding energy for donor impurities in the Pöschl-Teller quantum well are studied. The binding energy dependencies on the width of the quantum well, the hydrostatic pressure, the impurity position, the temperature, and the parameters of the confining potential are reported.

Alireza Hakimyfard; M. G. Barseghyan; C. A. Duque; A. A. Kirakosyan

2009-01-01

398

In the frame of the variational method and the effective-mass approximation, the effects of hydrostatic pressure and temperature on the binding energy for donor impurities in the Pöschl–Teller quantum well are studied. The binding energy dependencies on the width of the quantum well, the hydrostatic pressure, the impurity position, the temperature, and the parameters of the confining potential are reported.

Alireza Hakimyfard; M. G. Barseghyan; C. A. Duque; A. A. Kirakosyan

2009-01-01

399

Quantum Hall effect on centimeter scale chemical vapor deposited graphene films

Quantum Hall effect on centimeter scale chemical vapor deposited graphene films Tian Shen, Wei Wu, Qingkai Yu, Curt A. Richter, Randolph Elmquist et al. Citation: Appl. Phys. Lett. 99, 232110 (2011); doi://apl.aip.org/about/rights_and_permissions #12;Quantum Hall effect on centimeter scale chemical vapor deposited graphene films Tian Shen,1,2,a

Chen, Yong P.

400

Rashba effect in an asymmetric quantum dot in a magnetic field S. Bandyopadhyay

because of the Zeeman effect brought about by the magnetic field due to the contacts. We will callRashba effect in an asymmetric quantum dot in a magnetic field S. Bandyopadhyay Department that causes a Zeeman splitting of the electronic states in the quantum dot. We show that this Zeeman splitting

Cahay, Marc

401

A Proton Recoil Telescope Detector for Neutron Spectroscopy

A compact and versatile Proton Recoil Telescope (PRT) detector has been realized to measure neutron energy spectra in the range from few to hundred MeV. The PRT is a position sensitive detector made by: an active multilayer segmented plastic scintillator as neutron to proton converter, two silicon strip detectors for proton energy and position measurement and a final thick CsI(T1) scintillator to measure the residual proton energy. The detector has been tested with the {sup 13}C(d,n) reaction at Laboratori Nazionali del Sud using a 40 MeV deuteron beam.

Bocci, F. [INFN and Dipartimento di Fisica Nucleare e Teorica dell'Universita di Pavia (Italy); Dipartimento di Meccanica dell'Universita di Brescia and INFN Sezione di Pavia (Italy); Cinausero, M.; Rizzi, V.; Barbui, M.; Prete, G.; Andrighetto, A.; Lunardon, M.; Pesente, S. [INFN Laboratori Nazionali di Legnaro (Italy); Fontana, A.; Gemignian, G. [INFN and Dipartimento di Fisica Nucleare e Teorica dell'Universita di Pavia (Italy); Bonomi, G.; Donzella, A.; Zenoni, A. [Dipartimento di Meccanica dell'Universita di Brescia and INFN Sezione di Pavia (Italy); Fabris, D.; Morando, M.; Moretto, S.; Nebbia, G.; Viesti, G. [INFN and Dipartimento di Fisica dell'Universita di Padova (Italy)

2007-10-26

402

A Proton Recoil Telescope Detector for Neutron Spectroscopy

NASA Astrophysics Data System (ADS)

A compact and versatile Proton Recoil Telescope (PRT) detector has been realized to measure neutron energy spectra in the range from few to hundred MeV. The PRT is a position sensitive detector made by: an active multilayer segmented plastic scintillator as neutron to proton converter, two silicon strip detectors for proton energy and position measurement and a final thick CsI(T1) scintillator to measure the residual proton energy. The detector has been tested with the 13C(d,n) reaction at Laboratori Nazionali del Sud using a 40 MeV deuteron beam.

Bocci, F.; Cinausero, M.; Rizzi, V.; Fontana, A.; Barbui, M.; Bonomi, G.; Donzella, A.; Prete, G.; Fabris, D.; Andrighetto, A.; Gemignian, G.; Lunardon, M.; Morando, M.; Moretto, S.; Nebbia, G.; Pesente, S.; Viesti, G.; Zenoni, A.

2007-10-01

403

Detection Efficiency of the Clover Array for Recoil Decay Spectroscopy

NASA Astrophysics Data System (ADS)

The Clover Array for Recoil Decay Spectroscopy (CARDS) has been implemented in the newly commissioned facility Low-energy Radioactive Ion Beam Spectroscopy Station at Oak Ridge National Laboratory. Challenging experiments with very neutron rich isotopes near doubly magic ^78Ni has been performed. Quantitative analysis of the new data required a thorough measurement of the detection efficiency of the CARDS array using variety of the standard calibration sources. Of particular importance is observed high detection efficiency for gamma rays with energies in the range of 50-200 keV which has been achieved due to implementation of digital electronics. Examples of data from on-line experiments will be presented.

Engel, John; Al-Shudifat, Mahammad; Paulauskas, S. V.; Madurga, Miguel; Grzywacz, Robert

2011-10-01

404

Ho?ava-Lifshitz gravity and effective theory of the fractional quantum Hall effect

NASA Astrophysics Data System (ADS)

We show that Ho?ava-Lifshitz gravity theory can be employed as a covariant framework to build an effective field theory for the fractional quantum Hall effect that respects all the spacetime symmetries such as non-relativistic diffeomorphism invariance and anisotropic Weyl invariance as well as the gauge symmetry. The key to this formalism is a set of correspondence relations that maps all the field degrees of freedom in the Ho?ava-Lifshitz gravity theory to external background (source) fields among others in the effective action of the quantum Hall effect, according to their symmetry transformation properties. We originally derive the map as a holographic dictionary, but its form is independent of the existence of holographic duality. This paves the way for the application of Ho?ava-Lifshitz holography on fractional quantum Hall effect. Using the simplest holographic Chern-Simons model, we compute the low energy effective action at leading orders and show that it captures universal electromagnetic and geometric properties of quantum Hall states, including the Wen-Zee shift, Hall viscosity, angular momentum density and their relations. We identify the shift function in Ho?ava-Lifshitz gravity theory as minus of guiding center velocity and conjugate to guiding center momentum. This enables us to distinguish guiding center angular momentum density from the internal one, which is the sum of Landau orbit spin and intrinsic (topological) spin of the composite particles. Our effective action shows that Hall viscosity is minus half of the internal angular momentum density and proportional to Wen-Zee shift, and Hall bulk viscosity is half of the guiding center angular momentum density.

Wu, Chaolun; Wu, Shao-Feng

2015-01-01

405

Efficient Multi-Dimensional Simulation of Quantum Confinement Effects in Advanced MOS Devices

NASA Technical Reports Server (NTRS)

We investigate the density-gradient (DG) transport model for efficient multi-dimensional simulation of quantum confinement effects in advanced MOS devices. The formulation of the DG model is described as a quantum correction to the classical drift-diffusion model. Quantum confinement effects are shown to be significant in sub-100nm MOSFETs. In thin-oxide MOS capacitors, quantum effects may reduce gate capacitance by 25% or more. As a result, the inclusion or quantum effects in simulations dramatically improves the match between C-V simulations and measurements for oxide thickness down to 2 nm. Significant quantum corrections also occur in the I-V characteristics of short-channel (30 to 100 nm) n-MOSFETs, with current drive reduced by up to 70%. This effect is shown to result from reduced inversion charge due to quantum confinement of electrons in the channel. Also, subthreshold slope is degraded by 15 to 20 mV/decade with the inclusion of quantum effects via the density-gradient model, and short channel effects (in particular, drain-induced barrier lowering) are noticeably increased.

Biegel, Bryan A.; Rafferty, Conor S.; Ancona, Mario G.; Yu, Zhi-Ping

2000-01-01

406

The effects of the electron spin interaction on the pure instability and propagation modes of the quantum electrostatic waves are investigated in cold quantum electron plasmas. It is found that the influence of the electron spin interaction increases the group velocity of the propagation mode of the quantum electrostatic wave. In addition, it is shown that the electron spin interaction enhances the growth rate of the instability mode of the quantum electrostatic wave. It is also found that the effects of the electron spin interaction would be more important in the domain of small Fermi wave numbers.

Ki, Dae-Han; Jung, Young-Dae [Department of Applied Physics, Hanyang University, Ansan, Kyunggi-Do 426-791 (Korea, Republic of)

2011-09-19

407

Why are the effective equations of loop quantum cosmology so accurate?

NASA Astrophysics Data System (ADS)

We point out that the relative Heisenberg uncertainty relations vanish for noncompact spaces in homogeneous loop quantum cosmology. As a consequence, for sharply peaked states quantum fluctuations in the scale factor never become important, even near the bounce point. This shows why quantum backreaction effects remain negligible and explains the surprising accuracy of the effective equations in describing the dynamics of sharply peaked wave packets. This also underlines the fact that minisuperspace models—where it is global variables that are quantized—do not capture the local quantum fluctuations of the geometry.

Rovelli, Carlo; Wilson-Ewing, Edward

2014-07-01

408

Controllable effects of quantum fluctuations on spin free-induction decay at room temperature

Fluctuations of local fields cause decoherence of quantum objects. Usually at high temperatures, thermal noises are much stronger than quantum fluctuations unless the thermal effects are suppressed by certain techniques such as spin echo. Here we report the discovery of strong quantum-fluctuation effects of nuclear spin baths on free-induction decay of single electron spins in solids at room temperature. We find that the competition between the quantum and thermal fluctuations is controllable by an external magnetic field. These findings are based on Ramsey interference measurement of single nitrogen-vacancy center spins in diamond and numerical simulation of the decoherence, which are in excellent agreement. PMID:22666535

Liu, Gang-Qin; Pan, Xin-Yu; Jiang, Zhan-Feng; Zhao, Nan; Liu, Ren-Bao

2012-01-01

409

Quantum spin Hall effect and topological insulators for light

We show that free-space light has intrinsic quantum spin-Hall effect (QSHE) properties. These are characterized by a non-zero topological spin Chern number, and manifest themselves as evanescent modes of Maxwell equations. The recently discovered transverse spin of evanescent modes demonstrates spin-momentum locking stemming from the intrinsic spin-orbit coupling in Maxwell equations. As a result, any interface between free space and a medium supporting surface modes exhibits QSHE of light with opposite transverse spins propagating in opposite directions. In particular, we find that usual isotropic metals with surface plasmon-polariton modes represent natural 3D topological insulators for light. Several recent experiments have demonstrated transverse spin-momentum locking and spin-controlled unidirectional propagation of light at various interfaces with evanescent waves. Our results show that all these experiments can be interpreted as observations of the QSHE of light.

Bliokh, Konstantin Y

2015-01-01

410

The quantum anomalous Hall effect in kagomé lattices.

The quantum anomalous Hall (QAH) effect in kagomé lattices is investigated in the presence of both Rashba spin-orbit coupling and an exchange field. In addition to the gap at the Dirac points as found in graphene, a new topological energy gap is opened at the ? point. With the Fermi energy lying in the first gap, the Chern number = 2 as in graphene, whereas with it lying in the second one, = 1. The distribution of Berry curvature is obtained to reveal the nontrivial topological properties in momentum space. For stripes with 'armchair' and 'zigzag' edges, the topological characteristics of gapless edge states on the genus g = 2 Riemann surface are studied. The obtained nonzero winding numbers also demonstrate the QAH effe PMID:21852732

Zhang, Zhi-Yong

2011-09-14

411

Admittance measurements in the quantum Hall effect regime

NASA Astrophysics Data System (ADS)

In this work we present an admittance study of a two-dimensional electron gas (2DEG) in the quantum Hall effect (QHE) regime. We have studied several Hall bars in different contacts configurations in the frequency range 100 Hz-1 MHz. Our interpretation is based on the Landauer-Büttiker theory and takes into account both the capacitance and the topology of the coaxial cables which are connected to the sample holder. We show that we always observe losses through the capacitive impedance of the coaxial cables, except in the two contacts configuration in which the cable capacitance does not influence the admittance measurement of the sample. In this case, we measure the electrochemical capacitance of the 2DEG and show its dependence with the filling factor ?.

Hernández, C.; Consejo, C.; Chaubet, C.

2014-11-01

412

Quantum anomalous Hall effect in 2D organic topological insulators.

The quantum anomalous Hall effect (QAHE) is a fundamental transport phenomenon in the field of condensed-matter physics. Without an external magnetic field, spontaneous magnetization combined with spin-orbit coupling gives rise to a quantized Hall conductivity. So far, a number of theoretical proposals have been made to realize the QAHE, but all based on inorganic materials. Here, using first-principles calculations, we predict a family of 2D organic topological insulators for realizing the QAHE. Designed by assembling molecular building blocks of triphenyl-transition-metal compounds into a hexagonal lattice, this new class of organic materials is shown to have a nonzero Chern number and exhibits a gapless chiral edge state within the Dirac gap. PMID:23705732

Wang, Z F; Liu, Zheng; Liu, Feng

2013-05-10

413

Deformed Weyl–Heisenberg algebra and quantum decoherence effect

NASA Astrophysics Data System (ADS)

We study the dynamics of a catlike superposition of f-deformed coherent states under dissipative decoherence. For this purpose, we investigate two important categories of f-deformed coherent states: Gazeau–Klauder and displacement-type coherent states. In addition, we consider two deformation functions; one of them describes a harmonic oscillator in an infinite well and another corresponds to a harmonic oscillator in a quantum well with finite depth. The decoherence effects appeared through a dissipative interaction of the environment with the catlike states. In this study, we first show that the Gazeau–Klauder coherent state is more resistant under the decoherence process, in contrast to the displacement-type one, and second, that the potential range of the infinite well and the depth of potential possess a remarkable role in the decoherence process.

Dehdashti, Sh; Bagheri Harouni, M.; Mahdifar, A.; Roknizadeh, R.

2014-05-01

414

Magnetoelectric transport and quantum interference effect in ultrathin manganite films

The magnetoelectric transport behavior with respect to the thicknesses of ultrathin La{sub 0.9}Sr{sub 0.1}MnO{sub 3} films is investigated in detail. The metal-insulator phase transition, which has never been observed in bulk La{sub 0.9}Sr{sub 0.1}MnO{sub 3}, is found in ultrathin films with thicknesses larger than 6 unit cells. Low-temperature resistivity minima appeared in films with thicknesses less than 10 unit cells. This is attributed to the presence of quantum interference effects. These data suggest that the influence of the weak localization becomes much pronounced as the film thickness decreases from 16 to 8 unit cells.

Wang, Cong; Jin, Kui-juan, E-mail: kjjin@iphy.ac.cn; Gu, Lin; Lu, Hui-bin; Li, Shan-ming; Zhou, Wen-jia; Zhao, Rui-qiang; Guo, Hai-zhong; He, Meng; Yang, Guo-zhen [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

2014-04-21

415

Aharonov-Casher effect in quantum ring ensembles

NASA Astrophysics Data System (ADS)

We study the transport of electrons through a single-mode quantum ring with electric-field induced Rashba spin-orbit interaction that is subject to an in-plane magnetic field and weakly coupled to electron reservoirs. Modeling a ring array by ensemble averaging over a Gaussian distribution of energy-level positions, we predict slow conductance oscillations as a function of the Rashba interaction and electron density due to spin-orbit interaction induced beating of the spacings between the levels crossed by the Fermi energy. Our results agree with experiments by Nitta c.s. [J. Nitta, J. Takagi, F. Nagasawa, and M. Kohda, J. Phys.: Conference Series1742-659610.1088/1742-6596/302/1/012002 302, 012002 (2011) and Nagasawa (unpublished)], thereby providing an interpretation that differs from the ordinary Aharonov-Casher effect in a single ring.

Joibari, Fateme K.; Blanter, Ya. M.; Bauer, Gerrit E. W.

2013-09-01

416

Thermoelectric effects in molecular quantum dots with contacts

NASA Astrophysics Data System (ADS)

We consider the steady-state thermoelectric transport through a vibrating molecular quantum dot that is contacted to macroscopic leads. For moderate electron-phonon interaction strength and comparable electronic and phononic timescales, we investigate the impact of the formation of a local polaron on the thermoelectric properties of the junction. We apply a variational Lang-Firsov transformation and solve the equations of motion in the Kadanoff-Baym formalism up to second order in the dot-lead coupling parameter. We calculate the thermoelectric current and voltage for finite temperature differences in the resonant and inelastic tunneling regimes. For a near resonant dot level, the formation of a local polaron can boost the thermoelectric effect because of the Franck-Condon blockade. The line shape of the thermoelectric voltage signal becomes asymmetrical due to the varying polaronic character of the dot state and in the nonlinear transport regime, vibrational signatures arise.

Koch, T.; Loos, J.; Fehske, H.

2014-04-01

417

Magnetic quantum coherence effect in Ni4 molecular transistors.

We present a theoretical study of electron transport in Ni4 molecular transistors in the presence of Zeeman spin splitting and magnetic quantum coherence (MQC). The Zeeman interaction is extended along the leads which produces gaps in the energy spectrum which allow electron transport with spin polarized along a certain direction. We show that the coherent states in resonance with the spin up or down states in the leads induces an effective coupling between localized spin states and continuum spin states in the single molecule magnet and leads, respectively. We investigate the conductance at zero temperature as a function of the applied bias and magnetic field by means of the Landauer formula, and show that the MQC is responsible for the appearence of resonances. Accordingly, we name them MQC resonances. PMID:24918902

González, Gabriel; Leuenberger, Michael N

2014-07-01

418

Fractional quantum Hall effect in a dilute magnetic semiconductor

NASA Astrophysics Data System (ADS)

We report the observation of the fractional quantum Hall effect in the lowest Landau level of a two-dimensional electron system (2DES), residing in the diluted magnetic semiconductor Cd1-xMnxTe. The presence of magnetic impurities results in a giant Zeeman splitting leading to an unusual ordering of composite fermion Landau levels. In experiment, this results in an unconventional opening and closing of fractional gaps around the filling factor ? =3/2 as a function of an in-plane magnetic field, i.e., of the Zeeman energy. By including the s-d exchange energy into the composite Landau level spectrum the opening and closing of the gap at filling factor 5/3 can be modeled quantitatively. The widely tunable spin-splitting in a diluted magnetic 2DES provides a means to manipulate fractional states.

Betthausen, C.; Giudici, P.; Iankilevitch, A.; Preis, C.; Kolkovsky, V.; Wiater, M.; Karczewski, G.; Piot, B. A.; Kunc, J.; Potemski, M.; Wojtowicz, T.; Weiss, D.

2014-09-01

419

Quantum Spin-Hall Effect and Topologically Invariant Chern Numbers

We present a topological description of the quantum spin-Hall effect (QSHE) in a two-dimensional electron system on a honeycomb lattice with both intrinsic and Rashba spin-orbit couplings. We show that the topology of the band insulator can be characterized by a 2x2 matrix of first Chern integers. The nontrivial QSHE phase is identified by the nonzero diagonal matrix elements of the Chern number matrix (CNM). A spin Chern number is derived from the CNM, which is conserved in the presence of finite disorder scattering and spin nonconserving Rashba coupling. By using the Laughlin gedanken experiment, we numerically calculate the spin polarization and spin transfer rate of the conducting edge states and determine a phase diagram for the QSHE.

Sheng, D. N. [Department of Physics and Astronomy, California State University, Northridge, California 91330 (United States); Weng, Z. Y. [Center for Advanced Study, Tsinghua University, Beijing 100084 (China); Sheng, L. [Department of Physics and Texas Center for Superconductivity, University of Houston, Houston, Texas 77204 (United States); Haldane, F. D. M. [Department of Physics, Princeton University, Princeton, New Jersey 08544 (United States)

2006-07-21

420

'Dark Matter' as a Quantum Foam In-Flow Effect

The galactic `dark matter' effect is regarded as one of the major problems in fundamental physics. Here it is explained as a self-interaction dynamical effect of space itself, and so is not caused by an unknown form of matter. Because it was based on Kepler's Laws for the motion of the planets in the solar system the Newtonian theory of gravity was too restricted. A reformulation and generalisation of the Newtonian theory of gravity in terms of a velocity in-flow field, representing at a classical level the relative motion of a quantum-foam substructure to space, reveals a key dynamical feature of the phenomenon of gravity, namely the so called `dark matter' effect, which manifests not only in spiral galaxy rotation curves, but also in the borehole g anomaly, globular and galactic black holes, and in ongoing problems in improving the accuracy with which Newton's gravitational constant G is measured. The new theory of gravity involves an additional new dimensionless gravitational constant, and experimental data reveals this to be the fine structure constant. The new theory correctly predicts the globular cluster black hole masses, and that the `frame-dragging' effect is caused by vorticity in the in-flow. The relationship of the new theory of gravity to General Relativity which, like Newtonian gravity, does not have the `dark matter' dynamics, is explained.

Reginald T. Cahill

2005-08-25

421

Quantum Zero Point Effects in Water and Ice

NASA Astrophysics Data System (ADS)

Nuclear zero point effects have recently been shown to have an interesting quantum anomaly in ice. In particular, In hexagonal ice Ih, the lattice volume increases when H is replaced by D. This anomalous isotope shift of the lattice parameter increases with temperature, contrary to normal expectations [1]. Free energy calculations within the quasiharmonic approximation, with ab initio density functional theory, explain the origin of his anomaly. In this study, we extend our study to show that the anomalous isotope effect persists in amorphous ices, inherent structures of liquid water. This indicates that the anomalous isotope effect on the density of liquid water might be intrinsically related to the one observed in ice, even if their structures are radically different. In addition, we show that clathrate hydrides, also have this anomaly. We make a detailed analysis of the origin of the anomaly and study how the Hbond interaction and the vdW bond in liquid water are modified by these nuclear zero point effects. [1] B. Pamuk et. al, Phys. Rev. Lett. 108, 193003 (2012).

Pamuk, Betül; Fernández-Serra, Marivi

2013-03-01

422

Valley-Polarized Quantum Anomalous Hall Effect in Silicene

NASA Astrophysics Data System (ADS)

We find theoretically a new quantum state of matter—the valley-polarized quantum anomalous Hall state in silicene. In the presence of Rashba spin-orbit coupling and an exchange field, silicene hosts a quantum anomalous Hall state with Chern number C =2. We show that through tuning the Rashba spin-orbit coupling, a topological phase transition results in a valley-polarized quantum anomalous Hall state, i.e., a quantum state that exhibits the electronic properties of both the quantum valley Hall state (valley Chern number Cv=3) and quantum anomalous Hall state with C =-1. This finding provides a platform for designing dissipationless valleytronics in a more robust manner.

Pan, Hui; Li, Zhenshan; Liu, Cheng-Cheng; Zhu, Guobao; Qiao, Zhenhua; Yao, Yugui

2014-03-01

423

Valley-polarized quantum anomalous Hall effect in silicene.

We find theoretically a new quantum state of matter-the valley-polarized quantum anomalous Hall state in silicene. In the presence of Rashba spin-orbit coupling and an exchange field, silicene hosts a quantum anomalous Hall state with Chern number C=2. We show that through tuning the Rashba spin-orbit coupling, a topological phase transition results in a valley-polarized quantum anomalous Hall state, i.e., a quantum state that exhibits the electronic properties of both the quantum valley Hall state (valley Chern number Cv=3) and quantum anomalous Hall state with C=-1. This finding provides a platform for designing dissipationless valleytronics in a more robust manner. PMID:24679320

Pan, Hui; Li, Zhenshan; Liu, Cheng-Cheng; Zhu, Guobao; Qiao, Zhenhua; Yao, Yugui

2014-03-14

424

Noise characteristics of the Fano effect and the Fano-Kondo effect in triple quantum dots.

We theoretically compare transport properties of the Fano-Kondo effect with those of the Fano effect, focusing on the effect of a two-level state in a triple quantum dot (QD) system. We analyze shot noise characteristics in the Fano-Kondo region at zero temperature, and discuss the effect of strong electronic correlation in QDs. We found that the modulation of the Fano dip is strongly affected by the on-site Coulomb interaction in QDs, and stronger Coulomb interaction (Fano-Kondo case) induces larger noise. PMID:21825341

Tanamoto, T; Nishi, Y; Fujita, S

2009-04-01

425

Quantized anomalous Hall effect in two-dimensional ferromagnets: quantum Hall effect in metals.

We study the effect of disorder on the anomalous Hall effect (AHE) in two-dimensional ferromagnets. The topological nature of the AHE leads to the integer quantum Hall effect from a metal, i.e., the quantization of sigma(xy) induced by the localization except for the few extended states carrying Chern numbers. Extensive numerical study on a model reveals that Pruisken's two-parameter scaling theory holds even when the system has no gap with the overlapping multibands and without the uniform magnetic field. Therefore, the condition for the quantized AHE is given only by the Hall conductivity sigma(xy) without the quantum correction, i.e., /sigma(xy)/>e(2)/(2h). PMID:12785910

Onoda, Masaru; Nagaosa, Naoto

2003-05-23

426

Framing Anomaly in the Effective Theory of the Fractional Quantum Hall Effect

NASA Astrophysics Data System (ADS)

We consider the geometric part of the effective action for the fractional quantum Hall effect (FQHE). It is shown that accounting for the framing anomaly of the quantum Chern-Simons theory is essential to obtain the correct gravitational linear response functions. In the lowest order in gradients, the linear response generating functional includes Chern-Simons, Wen-Zee, and gravitational Chern-Simons terms. The latter term has a contribution from the framing anomaly which fixes the value of thermal Hall conductivity and contributes to the Hall viscosity of the FQH states on a sphere. We also discuss the effects of the framing anomaly on linear responses for non-Abelian FQH states.

Gromov, Andrey; Cho, Gil Young; You, Yizhi; Abanov, Alexander G.; Fradkin, Eduardo

2015-01-01

427

The effect of quantum confinement on tunneling field-effect transistors with high-? gate dielectric

NASA Astrophysics Data System (ADS)

In this letter, we study the impact of quantum confinement in double gate tunneling field-effect transistors with different body thicknesses in the presence of high-? gate dielectrics. Although better ON currents have been reported for these devices coming out from semiclassical simulations, the inclusion of quantum effects makes the formerly continuous conduction and valence bands become a discrete set of energy subbands, thus, increasing the effective bandgap, and consequently, reducing the current levels. If the high-? dielectric layer covers both the source and the drain, the band energy structure at the tunneling junction is modified (tunneling widths are increased), hence resulting in performance degradation. An optimal configuration seeking to improve ON currents would require low permittivity dielectrics over S/D regions along with high-? materials under the gates.

Padilla, J. L.; Gámiz, F.; Godoy, A.

2013-09-01

428

Framing anomaly in the effective theory of the fractional quantum Hall effect.

We consider the geometric part of the effective action for the fractional quantum Hall effect (FQHE). It is shown that accounting for the framing anomaly of the quantum Chern-Simons theory is essential to obtain the correct gravitational linear response functions. In the lowest order in gradients, the linear response generating functional includes Chern-Simons, Wen-Zee, and gravitational Chern-Simons terms. The latter term has a contribution from the framing anomaly which fixes the value of thermal Hall conductivity and contributes to the Hall viscosity of the FQH states on a sphere. We also discuss the effects of the framing anomaly on linear responses for non-Abelian FQH states. PMID:25615495

Gromov, Andrey; Cho, Gil Young; You, Yizhi; Abanov, Alexander G; Fradkin, Eduardo

2015-01-01

429

Exponential speed-up with a single bit of quantum information: Testing the quantum butterfly effect

We present an efficient quantum algorithm to measure the average fidelity decay of a quantum map under perturbation using a single bit of quantum information. Our algorithm scales only as the complexity of the map under investigation, so for those maps admitting an efficient gate decomposition, it provides an exponential speed up over known classical procedures. Fidelity decay is important in the study of complex dynamical systems, where it is conjectured to be a signature of quantum chaos. Our result also illustrates the role of chaos in the process of decoherence.

David Poulin; Robin Blume-Kohout; Raymond Laflamme; Harold Ollivier

2003-10-06

430

Localizationlike effect in two-dimensional alternate quantum walks with periodic coin operations

NASA Astrophysics Data System (ADS)

Exploiting multidimensional quantum walks as feasible platforms for quantum computation and quantum simulation attracts constantly growing attention from a broad experimental physics community. Here, we propose a two-dimensional quantum walk scheme with a single-qubit coin that presents, in the considered regimes, a strong localizationlike effect on the walker. The result could provide new possible directions for the implementation of quantum algorithms or from the point of view of quantum simulation. We characterize the localizationlike effect in terms of the parameters of a step-dependent qubit operation that acts on the coin space after any standard coin operation, showing that a proper choice can guarantee a nonnegligible probability of finding the walker in the origin even for large times. We finally discuss the robustness to imperfections, a qualitative relation with coherences behavior, and possible experimental realizations of this model with the current state-of-the-art settings.

Di Franco, Carlo; Paternostro, Mauro

2015-01-01

431

Experimental observation of the quantum Hall effect and Berry's phase in graphene

When electrons are confined in two-dimensional materials, quantum-mechanically enhanced transport phenomena such as the quantum Hall effect can be observed. Graphene, consisting of an isolated single atomic layer of graphite, is an ideal realization of such a two-dimensional system. However, its behaviour is expected to differ markedly from the well-studied case of quantum wells in conventional semiconductor interfaces. This difference

Yuanbo Zhang; Yan-Wen Tan; Horst L. Stormer; Philip Kim

2005-01-01

432

Collective Effects of Excitons in Multiple-Quantum-Well Bragg and Anti-Bragg Structures

NASA Astrophysics Data System (ADS)

Femtosecond degenerate four-wave mixing is used to investigate collective excitonic effects in radiatively coupled semiconductor multiple-quantum-well Bragg and anti-Bragg structures. The experimental and theoretical analysis of Bragg structures shows that the light-induced coupling causes a faster signal decay for increasing quantum-well numbers. For anti-Bragg structures, the predicted splitting of the excitonic resonances is observed in the four-wave-mixing spectrum causing quantum beats in the time-integrated signal.

Hübner, M.; Kuhl, J.; Stroucken, T.; Knorr, A.; Koch, S. W.; Hey, R.; Ploog, K.

1996-05-01

433

Gate-induced carrier delocalization in quantum dot field effect transistors.

We study gate-controlled, low-temperature resistance and magnetotransport in indium-doped CdSe quantum dot field effect transistors. We show that using the gate to accumulate electrons in the quantum dot channel increases the "localization product" (localization length times dielectric constant) describing transport at the Fermi level, as expected for Fermi level changes near a mobility edge. Our measurements suggest that the localization length increases to significantly greater than the quantum dot diameter. PMID:25171186

Turk, Michael E; Choi, Ji-Hyuk; Oh, Soong Ju; Fafarman, Aaron T; Diroll, Benjamin T; Murray, Christopher B; Kagan, Cherie R; Kikkawa, James M

2014-10-01

434

Quantum Interference Effects in Horava-Lifshitz Gravity

The relativistic quantum interference effects in the spacetime of slowly rotating object in the Ho\\v{r}ava-Lifshitz gravity as the Sagnac effect and phase shift of interfering particle in neutron interferometer are derived. We consider the extension of Kehagias-Sfetsos (KS) solution~\\cite{ks09} in the Ho\\v{r}ava-Lifshitz gravity for the slowly rotating gravitating object. Using the covariant Klein-Gordon equation in the nonrelativistic approximation, it is shown that the phase shift in the interference of particles includes the gravitational potential term with the KS parameter $\\omega$. It is found that in the case of the Sagnac effect, the influence of the KS parameter $\\omega$ is becoming important due to the fact that the angular velocity of the locally non rotating observer is increased in Ho\\v{r}ava gravity. From the results of the recent experiments~\\cite{holgeretal} we have obtained lower limit for the coupling KS constant as $\\omega \\simeq 1.25 \\cdot 10^{-25} \\rm{cm}^{2}$. Finally, as an example, we apply the obtained results to the calculation of the UCN (ultra-cold neutrons) energy level modification in the gravitational field of slowly rotating gravitating object in the Ho\\v{r}ava-Lifshitz gravity.

Abdullo Hakimov; Bobur Turimov; Ahmadjon Abdujabbarov; Bobomurot Ahmedov

2010-08-26

435

Effect of quantum nuclear motion on hydrogen bonding

This work considers how the properties of hydrogen bonded complexes, D-H....A, are modified by the quantum motion of the shared proton. Using a simple two-diabatic state model Hamiltonian, the analysis of the symmetric case, where the donor (D) and acceptor (A) have the same proton affinity, is carried out. For quantitative comparisons, a parametrization specific to the O-H....O complexes is used. The vibrational energy levels of the one-dimensional ground state adiabatic potential of the model are used to make quantitative comparisons with a vast body of condensed phase data, spanning a donor-acceptor separation (R) range of about 2.4-3.0 A, i.e., from strong to weak bonds. The position of the proton and its longitudinal vibrational frequency, along with the isotope effects in both are discussed. An analysis of the secondary geometric isotope effects, using a simple extension of the two-state model, yields an improved agreement of the predicted variation with R of frequency isotope effects. The role of the b...

McKenzie, Ross H; Athokpam, Bijyalaxmi; Ramesh, Sai G

2014-01-01

436

We present a systematic derivation and discussion of the practical formulae needed to design and interpret direct searches for nuclear recoil events caused by hypothetical weakly interacting dark matter particles. Modifications to the differential energy spectrum arise from the Earth's motion, recoil detection efficiency, instrumental resolution and threshold, multiple target elements, spin-dependent and coherent factors, and nuclear form factor. We

J. D. Lewin; P. F. Smith

1996-01-01

437

New measurement of the scintillation efficiency of low-energy nuclear recoils in liquid xenon

Particle detectors that use liquid xenon (LXe) as detection medium are among the leading technologies in the search for dark matter weakly interacting massive particles (WIMPs). A key enabling element has been the low-energy detection threshold for recoiling nuclei produced by the interaction of WIMPs in LXe targets. In these detectors, the nuclear recoil energy scale is based on the

G. Plante; E. Aprile; R. Budnik; B. Choi; K.-L. Giboni; L. W. Goetzke; R. F. Lang; K. E. Lim; A. J. Melgarejo Fernandez

2011-01-01

438

Optimal control of gun recoil in direct fire using magnetorheological absorbers

NASA Astrophysics Data System (ADS)

Optimal control of a gun recoil absorber is investigated for minimizing recoil loads and maximizing rate of fire. A multi-objective optimization problem was formulated by considering the mechanical model of the recoil absorber employing a spring and a magnetorheological (MR) damper. The damper forces are predicted by evaluating pressure drops using a nonlinear Bingham-plastic model. The optimization methodology provides multiple optimal design configurations with a trade-off between recoil load minimization and increased rate of fire. The configurations with low or high recoil loads imply low or high rate of fire, respectively. The gun recoil absorber performance is also analyzed for perturbations in the firing forces. The adaptive control of the MR damper for varying gun firing forces provides a smooth operation by returning the recoil mass to its battery position (ready to reload and fire) without incurring an end-stop impact. Furthermore, constant load transmissions are observed with respect to the recoil stroke by implementing optimal control during the simulated firing events.

Singh, Harinder J.; Wereley, Norman M.

2014-05-01

439

Serial intravascular ultrasound studies fail to show evidence of chronic Palmaz-Schatz stent recoil

Serial IVUS analysis after intervention and at follow-up showed that late recoil of the Palmaz-Schatz stent rarely occurred, and when it did occur, late stent recoil was minimal. The dominant mechanism of late lumen loss in this setting was neointimal hyperplasia.

Jack A. Painter; Gary S. Mintz; S. Chiu Wong; Jeffrey J. Popma; Augusto D. Pichard; Kenneth M. Kent; Lowell F. Satler; Martin B. Leon

1995-01-01

440

Effective-field-theory model for the fractional quantum Hall effect

NASA Technical Reports Server (NTRS)

Starting directly from the microscopic Hamiltonian, a field-theory model is derived for the fractional quantum Hall effect. By considering an approximate coarse-grained version of the same model, a Landau-Ginzburg theory similar to that of Girvin (1986) is constructed. The partition function of the model exhibits cusps as a function of density. It is shown that the collective density fluctuations are massive.

Zhang, S. C.; Hansson, T. H.; Kivelson, S.

1989-01-01

441

Photonic realization of nonlocal memory effects and non-Markovian quantum probes

The study of open quantum systems is important for fundamental issues of quantum physics as well as for technological applications such as quantum information processing. Recent developments in this field have increased our basic understanding on how non-Markovian effects influence the dynamics of an open quantum system, paving the way to exploit memory effects for various quantum control tasks. Most often, the environment of an open system is thought to act as a sink for the system information. However, here we demonstrate experimentally that a photonic open system can exploit the information initially held by its environment. Correlations in the environmental degrees of freedom induce nonlocal memory effects where the bipartite open system displays, counterintuitively, local Markovian and global non-Markovian character. Our results also provide novel methods to protect and distribute entanglement, and to experimentally quantify correlations in photonic environments.

Liu, Bi-Heng; Cao, Dong-Yang; Huang, Yun-Feng; Li, Chuan-Feng; Guo, Guang-Can; Laine, Elsi-Mari; Breuer, Heinz-Peter; Piilo, Jyrki

2013-01-01

442

Quantum size effects and transport phenomena in PbSe quantum wells and PbSe/EuS superlattices

It is established that the room-temperature dependences of transport properties on the total thickness of PbSe layers d in PbSe/EuS superlattices exhibit an oscillatory behavior. It is shown that the oscillation period ?d practically coincides with the period of the thickness oscillations observed earlier in single PbSe/EuS quantum well. The non-monotonic character of these dependences is attributed to quantum size effects. The theoretically estimated and experimentally determined ?d values are in good agreement.

Rogacheva, E. I.; Nashchekina, O. N.; Ol'khovskaya, S. I.; Sipatov, A. Yu. [National technical university Kharkov polytechnic institute, 21 Frunze St., Kharkov, 61002 (Ukraine); Dresselhaus, M. S. [Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge MA 02139 (United States)

2013-12-04

443

An analytical model for square GAA MOSFETs including quantum effects

NASA Astrophysics Data System (ADS)

In this paper we introduce an analytical model for square Gate-All-Around (GAA) MOSFETs including quantum effects. With the model developed, it is possible to provide an analytical description of the 2D inversion charge distribution function (ICDF) in square GAA MOSFETs of different sizes and for all the operational regimes. The accuracy of the model is verified by comparing the data with that obtained by means of a 2D numerical simulator that self-consistently solves the Poisson and Schrödinger equations. The expressions presented here are useful to achieve a good description of the physics of these transistors; in particular, of the quantization effects on the inversion charge. The analytical ICDF obtained is used to calculate important parameters from the device compact modeling viewpoint, such as the inversion charge centroid and the gate-to-channel capacitance, which are modeled for different device geometries and biases. The model presented accurately reproduces the simulation results for the devices under study and for different operational regimes.

Moreno, E.; Roldán, J. B.; Ruiz, F. G.; Barrera, D.; Godoy, A.; Gámiz, F.

2010-11-01

444

Effective quantum memory Hamiltonian from local two-body interactions

In [Phys. Rev. A 88, 062313 (2013)] we proposed and studied a model for a self-correcting quantum memory in which the energetic cost for introducing a defect in the memory grows without bounds as a function of system size. This positive behavior is due to attractive long-range interactions mediated by a bosonic field to which the memory is coupled. The crucial ingredients for the implementation of such a memory are the physical realization of the bosonic field as well as local five-body interactions between the stabilizer operators of the memory and the bosonic field. Here, we show that both of these ingredients appear in a low-energy effective theory of a Hamiltonian that involves only two-body interactions between neighboring spins. In particular, we consider the low-energy, long-wavelength excitations of an ordered Heisenberg ferromagnet (magnons) as a realization of the bosonic field. Furthermore, we present perturbative gadgets for generating the required five-spin operators. Our Hamiltonian involving only local two-body interactions is thus expected to exhibit self-correcting properties as long as the noise affecting it is in the regime where the effective low-energy description remains valid.

Adrian Hutter; Fabio L. Pedrocchi; James R. Wootton; Daniel Loss

2014-05-13

445

Electrostatically Shielded Quantum Confined Stark Effect Inside Polar Nanostructures

The effect of electrostatic shielding of the polarization fields in nanostructures at high carrier densities is studied. A simplified analytical model, employing screened, exponentially decaying polarization potentials, localized at the edges of a QW, is introduced for the ES-shielded quantum confined Stark effect (QCSE). Wave function trapping within the Debye-length edge-potential causes blue shifting of energy levels and gradual elimination of the QCSE red-shifting with increasing carrier density. The increase in the e?h wave function overlap and the decrease of the radiative emission time are, however, delayed until the “edge-localization” energy exceeds the peak-voltage of the charged layer. Then the wave function center shifts to the middle of the QW, and behavior becomes similar to that of an unbiased square QW. Our theoretical estimates of the radiative emission time show a complete elimination of the QCSE at doping densities ?1020 cm?3, in quantitative agreement with experimental measurements. PMID:20596407

2009-01-01

446

Strong-coupling topological Josephson effect in quantum wires

NASA Astrophysics Data System (ADS)

We investigate the Josephson effect for a setup with two lattice quantum wires featuring Majorana zero energy boundary modes at the tunnel junction. In the weak-coupling regime, the exact solution reproduces the perturbative result for the energy containing a contribution ˜ ± cos(?/2) relative to the tunneling of paired Majorana fermions. As the tunnel amplitude g grows relative to the hopping amplitude w, the gap between the energy levels gradually diminishes until it closes completely at the critical value {g}_{{c}}=\\sqrt{2}w. At this point the Josephson energies have the principal values {E}_{m \\sigma }=2 \\sigma \\sqrt{2}w\\cos [\\phi /6+2 \\pi (m-1)/3], where m =- 1,0,1 and ? =± 1, a result not following from perturbation theory. It represents a transparent regime where three Bogoliubov states merge, leading to additional degeneracies of the topologically nontrivial ground state with an odd number of Majorana fermions at the end of each wire. We also obtain the exact tunnel currents for a fixed parity of the eigenstates. The Josephson current shows the characteristic 4? periodicity expected for a topological Josephson effect. We discuss the additional features of the current associated with a closure of the energy gap between the energy levels.

Nogueira, Flavio S.; Eremin, Ilya

2012-08-01

447

Piezoelectric effect in InAs/InP quantum rod nanowires grown on silicon substrate

We report on the evidence of a strain-induced piezoelectric field in wurtzite InAs/InP quantum rod nanowires. This electric field, caused by the lattice mismatch between InAs and InP, results in the quantum confined Stark effect and, as a consequence, affects the optical properties of the nanowire heterostructure. It is shown that the piezoelectric field can be screened by photogenerated carriers or removed by increasing temperature. Moreover, a dependence of the piezoelectric field on the quantum rod diameter is observed in agreement with simulations of wurtzite InAs/InP quantum rod nanowire heterostructures.

Anufriev, Roman; Chauvin, Nicolas, E-mail: nicolas.chauvin@insa-lyon.fr; Bru-Chevallier, Catherine [Université de Lyon, Institut des Nanotechnologies de Lyon (INL)-UMR5270-CNRS, INSA-Lyon, 7 avenue Jean Capelle, 69621 Villeurbanne (France); Khmissi, Hammadi [Université de Monastir, Laboratoire de Micro-Optoélectronique et Nanostructures (LMON), Faculté des Sciences, Avenue de l'environnement, 5019 Monastir (Tunisia); Naji, Khalid; Gendry, Michel [Université de Lyon, Institut des Nanotechnologies de Lyon (INL)-UMR5270-CNRS, Ecole Centrale de Lyon, 36 avenue Guy de Collongue, 69134 Ecully (France); Patriarche, Gilles [Laboratoire de Photonique et de Nanostructures (LPN), UPR20-CNRS, route de Nozay, 91460 Marcoussis (France)

2014-05-05

448

Piezoelectric effect in InAs/InP quantum rod nanowires grown on silicon substrate

NASA Astrophysics Data System (ADS)

We report on the evidence of a strain-induced piezoelectric field in wurtzite InAs/InP quantum rod nanowires. This electric field, caused by the lattice mismatch between InAs and InP, results in the quantum confined Stark effect and, as a consequence, affects the optical properties of the nanowire heterostructure. It is shown that the piezoelectric field can be screened by photogenerated carriers or removed by increasing temperature. Moreover, a dependence of the piezoelectric field on the quantum rod diameter is observed in agreement with simulations of wurtzite InAs/InP quantum rod nanowire heterostructures.

Anufriev, Roman; Chauvin, Nicolas; Khmissi, Hammadi; Naji, Khalid; Patriarche, Gilles; Gendry, Michel; Bru-Chevallier, Catherine

2014-05-01

449

Effect of deconfinement on resonant transport in quantum wires A. Ramsak J. Stefan Institute, SI through quantum wires with two con- strictions is investigated. It is shown that the increase in resonance on the energy temperature scale for which resonances may be observed. S0163-1829 98 07231-2 I. INTRODUCTION

Ramsak, Anton

450

Acceleration of positrons by a relativistic electron beam in the presence of quantum effects

Using the quantum magnetohydrodynamic model and obtaining the dispersion relation of the Cherenkov and cyclotron waves, the acceleration of positrons by a relativistic electron beam is investigated. The Cherenkov and cyclotron acceleration mechanisms of positrons are compared together. It is shown that growth rate and, therefore, the acceleration of positrons can be increased in the presence of quantum effects.

Niknam, A. R. [Laser and Plasma Research Institute, Shahid Beheshti University, G.C., Tehran (Iran, Islamic Republic of)] [Laser and Plasma Research Institute, Shahid Beheshti University, G.C., Tehran (Iran, Islamic Republic of); Aki, H.; Khorashadizadeh, S. M. [Physics Department, Birjand University, Birjand (Iran, Islamic Republic of)] [Physics Department, Birjand University, Birjand (Iran, Islamic Republic of)

2013-09-15

451

Effects of scattering centers on the energy spectrum of a quantum dot

Repulsive scattering centers in quantum dots have profound effects on the energy spectrum of a quantum dot in a magnetic field. The symmetry-breaking electron-impurity potentials cause lifting of the degeneracy, level repulsion, etc. in the energy spectrum and angular momentum selection rules are found that govern those anticrossings of the energy levels. We also study the optical absorption spectra in

V. Halonen; P. Hyvonen; P. Pietilainen; Tapash Chakraborty

452

DARK MATTER AND DARK ENERGY AS EFFECTS OF QUANTUM GRAVITY Max I. Fomitchev1

DARK MATTER AND DARK ENERGY AS EFFECTS OF QUANTUM GRAVITY Max I. Fomitchev1 Submitted March 12th , 2004 ABSTRACT I present a theory of quantum gravity based on the principle of gravitational energy fluctuations. Gravitational energy fluctuations Â gravitons Â are responsible for elastic scattering

Giles, C. Lee

453

Ab initio statistical mechanics of surface adsorption and desorption. II. Nuclear quantum effects

Ab initio statistical mechanics of surface adsorption and desorption. II. Nuclear quantum effects D-integral formulation of quantum statistical mechanics can be used to construct practical ab initio techniques statistical-mechanical approximations, apart from the treat- ment of the nuclei as classical particles

AlfÃ¨, Dario

454

Coulomb Oscillations and Hall Effect in Quasi-2D Graphite Quantum Dots

Coulomb Oscillations and Hall Effect in Quasi-2D Graphite Quantum Dots J. Scott Bunch, Yuval Yaish-temperature electrical transport measurements on gated, quasi-2D graphite quantum dots. In devices with low contact that electrons in mesoscopic graphite pieces are delocalized over nearly the whole graphite piece down to low

McEuen, Paul L.

455

Two-Dimensional Polysilicon Quantum-Mechanical Effects in Double-Gate SOI

with very-thin gate dielectrics since a deep quantum well is formed near the poly/oxide interface when sidewalls, which is common when the gate dopant is boron (i.e. PMOS), since boron atoms in silicon haveTwo-Dimensional Polysilicon Quantum-Mechanical Effects in Double-Gate SOI Chang-Hoon Choi, Zhiping

Dutton, Robert W.

456

Quantum-size effects on the band edge of CdTe clusters in glass

The measurement of quantum-size behavior in semiconductor crystals has been examined through an analysis of the size dependence of the semiconductor's absorption edge. In past studies, there appeared to be little agreement between theory and experiment for very small crystals. In this paper, the effects of crystal-size distribution and tunneling of the carrier wave functions into the quantum well barrier

B. G. Potter Jr.; J. H. Simmons; P. Kumar; C. J. Stanton

1994-01-01

457

A general scheme is established within the effective-mass approximation to calculate systematically the excitonic energy spectra in a semiconductor quantum dot including the dielectric confinement effect. This effect is found to appear most pronounced in the quantum-dot structure in comparison with the quantum-well and quantum-wire structures. A formula of the lowest exciton energy in the strong confinement regime is derived

T. Takagahara

1993-01-01

458

NASA Astrophysics Data System (ADS)

A theoretical study is reported of electron transport at finite temperature in a double quantum dot (DQD) capacitively coupled to a quantum point contact (QPC) for the measurement of the DQD charge state. Starting from a Hamiltonian model, a master equation is obtained for the stochastic process taking place in the DQD while the QPC is at or away from equilibrium, allowing us to study the measurement back-action of the QPC onto the DQD. The QPC is treated nonperturbatively in our analysis. Effective fluctuation theorems are established for the full counting statistics of the DQD current under different limiting conditions. These fluctuation theorems hold with respect to an effective affinity characterizing the nonequilibrium environment of the DQD and differing from the applied voltage if the QPC is out of equilibrium. The effective affinity may even change its sign if the Coulomb drag of the QPC reverses the DQD current. The thermodynamic implications of the effective fluctuation theorems are discussed.

Bulnes Cuetara, Gregory; Esposito, Massimiliano; Schaller, Gernot; Gaspard, Pierre

2013-09-01

459

Study of impurity position effect in pyramid and cone like quantum dots

NASA Astrophysics Data System (ADS)

In the present work, we have studied the effect of impurity position on energy levels, the donor binding energy and third harmonic generation of a pyramid and a cone like quantum dot. For this goal, we have calculated the energy levels, wave functions and binding energy using finite element method for various impurity positions. Our results show that the impurity location plays an important and considerable role in the electronic and optical properties in a pyramid and a cone like quantum dot. We found that the third harmonic generation and binding energy of both quantum dots have a maximum value at a special impurity position. The special impurity location is different for the two quantum dots. Also, we have deduced that the third harmonic generation of a cone like quantum dot is larger than a pyramid quantum dot for same volumes and heights.

Khordad, Reza; Bahramiyan, Hossein

2014-08-01

460

Elementary framework for cold field emission: Incorporation of quantum-confinement effects

Although the Fowler-Nordheim (FN) equation serves as the foundation of cold field emission theory, it may not be suitable for predicting the emitted current density (ECD) from emitters with a quantum-confined electron supply. This work presents an analytical framework for treating cold field emission from metals that includes the effects of a quantum-confined electron supply. Within the framework, quantum confinement in emitters is classified into transverse and normal quantum confinement based on the orientation of the confinement relative to the emission direction. The framework is used to generate equations predicting the ECD from rectangular and cylindrical emitter geometries comprised of electron supplies of reduced dimensionality. Transverse quantum confinement of the electron supply leads to a reduction in the total ECD as transverse emitter dimensions decrease and normal quantum confinement results in an oscillatory ECD as a function of the normal quantum well width. Incorporating a geometry-dependent field enhancement factor into the model reveals an optimal transverse well width for which quantum confinement of the electron supply and field enhancement equally affect the ECD and a maximum total ECD for the emitter geometry at a given applied field is obtained. As a result, the FN equation over-predicts the ECD from emitters with transverse dimensions under approximately 5?nm, and in those cases, geometry-specific ECD equations incorporating quantum-confinement effects should be employed instead.

Patterson, A. A., E-mail: apatters@mit.edu; Akinwande, A. I. [Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Microsystems Technology Laboratories, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2013-12-21