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Sample records for mott scattering

  1. Coherent light scattering from a two-dimensional Mott insulator.

    PubMed

    Weitenberg, Christof; Schauss, Peter; Fukuhara, Takeshi; Cheneau, Marc; Endres, Manuel; Bloch, Immanuel; Kuhr, Stefan

    2011-05-27

    We experimentally demonstrate coherent light scattering from an atomic Mott insulator in a two-dimensional lattice. The far-field diffraction pattern of small clouds of a few hundred atoms was imaged while simultaneously laser cooling the atoms with the probe beams. We describe the position of the diffraction peaks and the scaling of the peak parameters by a simple analytic model. In contrast to Bragg scattering, scattering from a single plane yields diffraction peaks for any incidence angle. We demonstrate the feasibility of detecting spin correlations via light scattering by artificially creating a one-dimensional antiferromagnetic order as a density wave and observing the appearance of additional diffraction peaks.

  2. Mott scattering in an elliptically polarized laser field

    SciTech Connect

    Attaourti, Y.; Manaut, B.; Taj, S.

    2004-08-01

    We study Mott scattering in the presence of a strong elliptically polarized field. Using the first Born approximation and the Dirac-Volkov states for the electron, we obtain an analytic formula for the unpolarized differential cross section. This generalizes the results found for the linearly polarized field by Li et al. [ 67, 063409 (2003)] and for the circularly polarized field by Attaourti and Manaut [ 68, 067401 (2003)].

  3. Mott scattering of polarized electrons in a strong laser field

    SciTech Connect

    Manaut, B.; Taj, S.; Attaourti, Y.

    2005-04-01

    We present analytical and numerical results of the relativistic calculation of the transition matrix element S{sub fi} and differential cross sections for Mott scattering of initially polarized Dirac particles (electrons) in the presence of a strong laser field with linear polarization. We use exact Dirac-Volkov wave functions to describe the dressed electrons and the collision process is treated in the first Born approximation. The influence of the laser field on the degree of polarization of the scattered electron is reported.

  4. Resonant inelastic x-ray scattering in a Mott insulator

    NASA Astrophysics Data System (ADS)

    Pakhira, Nandan; Freericks, J. K.; Shvaika, A. M.

    2012-09-01

    We calculate the resonant inelastic x-ray scattering (RIXS) response in a Mott insulator, which is described by the Falicov-Kimball model. The model can be solved exactly within the single site dynamical mean-field theory (DMFT) approximation and the RIXS response can also be calculated accurately up to a local background correction. We find that on resonance the RIXS response is greatly enhanced. The response systematically evolves from a single-peak structure, arising due to relaxation processes within the lower Hubbard band, to a two-peak structure, arising due to relaxation processes within the upper Hubbard band and across the Mott gap into the lower Hubbard band. This occurs as we vary the incident photon frequency to allow excitations from the lower Hubbard band to the upper Hubbard band. The charge transfer excitations are found to disperse monotonically as we go from the center of the Brillouin zone towards the zone corner. These correlation-induced features have been observed by Hasan [Science0036-807510.1126/science.288.5472.1811 288, 1811 (2000)] and many other experimentalists in RIXS measurements over various transition-metal oxide compounds. They are found to be robust and survive even for large Auger lifetime broadening effects that can mask the many-body effects by smearing out spectral features. As a comparison, we also calculate the dynamic structure factor for this model, which is proportional to the nonresonant part of the response, and does not show these specific signatures.

  5. Concept of a multichannel spin-resolving electron analyzer based on Mott scattering

    PubMed Central

    Strocov, Vladimir N.; Petrov, Vladimir N.; Dil, J. Hugo

    2015-01-01

    The concept of a multichannel electron spin detector based on optical imaging principles and Mott scattering (iMott) is presented. A multichannel electron image produced by a standard angle-resolving (photo) electron analyzer or microscope is re-imaged by an electrostatic lens at an accelerating voltage of 40 kV onto the Au target. Quasi-elastic electrons bearing spin asymmetry of the Mott scattering are imaged by magnetic lenses onto position-sensitive electron CCDs whose differential signals yield the multichannel spin asymmetry image. Fundamental advantages of this concept include acceptance of inherently divergent electron sources from the electron analyzer or microscope focal plane as well as small aberrations achieved by virtue of high accelerating voltages, as demonstrated by extensive ray-tracing analysis. The efficiency gain compared with the single-channel Mott detector can be a factor of more than 104 which opens new prospects of spin-resolved spectroscopies in application not only to standard bulk and surface systems (Rashba effect, topological insulators, etc.) but also to buried heterostructures. The simultaneous spin detection combined with fast CCD readout enables efficient use of the iMott detectors at X-ray free-electron laser facilities. PMID:25931087

  6. Detection of spin-resolved electronic structures from a buried ferromagnetic layer utilizing forward Mott scattering

    SciTech Connect

    Ueda, S.; Mizuguchi, M.; Kojima, T.; Takanashi, K.; Ishimaru, S.; Tsujikawa, M.; Shirai, M.

    2014-03-31

    We report ultrahigh-resolution spin-resolved hard X-ray photoemission (HAXPES) for a buried FeNi alloy film. By utilizing the forward Mott scattering in a Au layer on FeNi, our spin-resolved HAXPES method does not require a standard spin detector and allows us to use the multi-channel electron detection system for the high-efficient electron detection as used in conventional photoemission spectroscopy. A combination of the forward Mott scattering and multi-channel detection leads us to measure a clear spin polarization as well as spin-resolved majority and minority states in the Fe 2p core-level spectra without using the standard spin detector. This method enables us to measure spin-resolved core-level spectra for buried ferromagnetic materials.

  7. Enhanced Thermoelectric Power in Graphene: Violation of the Mott Relation by Inelastic Scattering.

    PubMed

    Ghahari, Fereshte; Xie, Hong-Yi; Taniguchi, Takashi; Watanabe, Kenji; Foster, Matthew S; Kim, Philip

    2016-04-01

    We report the enhancement of the thermoelectric power (TEP) in graphene with extremely low disorder. At high temperature we observe that the TEP is substantially larger than the prediction of the Mott relation, approaching to the hydrodynamic limit due to strong inelastic scattering among the charge carriers. However, closer to room temperature the inelastic carrier-optical-phonon scattering becomes more significant and limits the TEP below the hydrodynamic prediction. We support our observation by employing a Boltzmann theory incorporating disorder, electron interactions, and optical phonons. PMID:27081996

  8. Enhanced Thermoelectric Power in Graphene: Violation of the Mott Relation by Inelastic Scattering

    NASA Astrophysics Data System (ADS)

    Ghahari, Fereshte; Xie, Hong-Yi; Taniguchi, Takashi; Watanabe, Kenji; Foster, Matthew S.; Kim, Philip

    2016-04-01

    We report the enhancement of the thermoelectric power (TEP) in graphene with extremely low disorder. At high temperature we observe that the TEP is substantially larger than the prediction of the Mott relation, approaching to the hydrodynamic limit due to strong inelastic scattering among the charge carriers. However, closer to room temperature the inelastic carrier-optical-phonon scattering becomes more significant and limits the TEP below the hydrodynamic prediction. We support our observation by employing a Boltzmann theory incorporating disorder, electron interactions, and optical phonons.

  9. Spin Correlations and the Mott-Hubbard Metal-Insulator Transition in Vanadium Trioxide: a Neutron Scattering Study.

    NASA Astrophysics Data System (ADS)

    Bao, Wei

    rm V_2O_3 is a canonical Mott system where strong correlations among electrons drive spectacular metal-insulator transitions and the metallic rm V_2O_3 has served as a prototype of the Brinkman-Rice strongly correlated Fermi liquid. Research in Mott-Hubbard systems has largely focused on charge dynamics. Spin dynamics is widely assumed as described by localized spin fluctuations on the grounds that the electrons in the metal are nearly localized near the Mott transition. Discovery of high T_{C} superconductivity in cuprates and the subsequent attribution of spin fluctuations in pairing electrons demand a better understanding of strongly correlated electron systems in general and spin dynamics of these systems in particular. Using magnetic neutron scattering, we discovered an incommensurate spin density wave in doping stabilized metallic V_{2-y}O _3 at low temperatures, which appears not to be directly related to the antiferromagnetic order in the insulating rm V_2O_3. This weak ordering phenomenon at low temperatures is accompanied by energetic spin fluctuations with large spectral weight throughout the paramagnetic metallic phase of rm V_2O_3, reflecting the itinerant nature of magnetism with an energy scale related to the Fermi energy, in contrast to the conventional k _{B}T ~ J of a localized -spin model, even on the verge of Mott transition. Spin fluctuations in the paramagnetic insulating (V _{1-x}Cr_{x })_2O_3 were discovered to relate to those of paramagnetic metallic rm V_2O_3 rather than to the antiferromagnetic order of the low temperature insulating phase. The short correlation length in the paramagnetic insulator was discovered to be controlled by a mechanism other than thermal spin fluctuations. This unusual property invalidates previous claims of explaining the phase diagram of rm V_2O_3 based on a one-band Hubbard model and indicates the important physical consequences of degenerate Hubbard bands in rm V_2O_3. Work in this dissertation was performed

  10. Charge-transfer and Mott-Hubbard Excitations in FeBo{sub 3} : Fe K-edge resonant Inelastic x-ray scattering study.

    SciTech Connect

    Kim, J.; Shvydko, Y.

    2011-06-06

    Momentum-resolved resonant inelastic x-ray scattering (RIXS) spectroscopy has been carried out successfully at the Fe K-edge for the first time. The RIXS spectra of a FeBO{sub 3} single crystal reveal a wealth of information on {approx} 1-10 eV electronic excitations. The IXS signal resonates when the incident photon energy approaches the pre-edge (1s{sup -}-3d) and the main-edge (1s{sup -}-4p) of the Fe K-edge absorption spectrum. The RIXS spectra measured at the pre-edge and the main-edge show quantitatively different dependences on the incident photon energy, momentum transfer, photon polarization, and temperature. We present a multielectron analysis of the Mott-Hubbard (MH) and charge transfer (CT) excitations, and calculate their energies. Electronic excitations observed in the pre-edge and main-edge RIXS spectra are interpreted as MH and CT excitations, respectively. We propose the electronic structure around the chemical potential in FeBO{sub 3} based on the experimental data.

  11. Fragile Mott insulators.

    PubMed

    Yao, Hong; Kivelson, Steven A

    2010-10-15

    We prove that there exists a class of crystalline insulators, which we call "fragile Mott insulators," which are not adiabatically connected to any sort of band insulator provided time-reversal and certain point-group symmetries are respected, but which are otherwise unspectacular in that they exhibit no topological order nor any form of fractionalized quasiparticles. Different fragile Mott insulators are characterized by different nontrivial one-dimensional representations of the crystal point group. We illustrate this new type of insulators with two examples: the d Mott insulator discovered in the checkerboard Hubbard model at half-filling and the Affleck-Kennedy-Lieb-Tasaki insulator on the square lattice.

  12. Weyl Mott Insulator.

    PubMed

    Morimoto, Takahiro; Nagaosa, Naoto

    2016-01-01

    Relativistic Weyl fermion (WF) often appears in the band structure of three dimensional magnetic materials and acts as a source or sink of the Berry curvature, i.e., the (anti-)monopole. It has been believed that the WFs are stable due to their topological indices except when two Weyl fermions of opposite chiralities annihilate pairwise. Here, we theoretically show for a model including the electron-electron interaction that the Mott gap opens for each WF without violating the topological stability, leading to a topological Mott insulator dubbed Weyl Mott insulator (WMI). This WMI is characterized by several novel features such as (i) energy gaps in the angle-resolved photo-emission spectroscopy (ARPES) and the optical conductivity, (ii) the nonvanishing Hall conductance, and (iii) the Fermi arc on the surface with the penetration depth diverging as approaching to the momentum at which the Weyl point is projected. Experimental detection of the WMI by distinguishing from conventional Mott insulators is discussed with possible relevance to pyrochlore iridates. PMID:26822023

  13. Weyl Mott Insulator

    PubMed Central

    Morimoto, Takahiro; Nagaosa, Naoto

    2016-01-01

    Relativistic Weyl fermion (WF) often appears in the band structure of three dimensional magnetic materials and acts as a source or sink of the Berry curvature, i.e., the (anti-)monopole. It has been believed that the WFs are stable due to their topological indices except when two Weyl fermions of opposite chiralities annihilate pairwise. Here, we theoretically show for a model including the electron-electron interaction that the Mott gap opens for each WF without violating the topological stability, leading to a topological Mott insulator dubbed Weyl Mott insulator (WMI). This WMI is characterized by several novel features such as (i) energy gaps in the angle-resolved photo-emission spectroscopy (ARPES) and the optical conductivity, (ii) the nonvanishing Hall conductance, and (iii) the Fermi arc on the surface with the penetration depth diverging as approaching to the momentum at which the Weyl point is projected. Experimental detection of the WMI by distinguishing from conventional Mott insulators is discussed with possible relevance to pyrochlore iridates. PMID:26822023

  14. Extrapolation procedures in Mott electron polarimetry

    NASA Technical Reports Server (NTRS)

    Gay, T. J.; Khakoo, M. A.; Brand, J. A.; Furst, J. E.; Wijayaratna, W. M. K. P.; Meyer, W. V.; Dunning, F. B.

    1992-01-01

    In standard Mott electron polarimetry using thin gold film targets, extrapolation procedures must be used to reduce the experimentally measured asymmetries A to the values they would have for scattering from single atoms. These extrapolations involve the dependent of A on either the gold film thickness or the maximum detected electron energy loss in the target. A concentric cylindrical-electrode Mott polarimeter, has been used to study and compare these two types of extrapolations over the electron energy range 20-100 keV. The potential systematic errors which can result from such procedures are analyzed in detail, particularly with regard to the use of various fitting functions in thickness extrapolations, and the failure of perfect energy-loss discrimination to yield accurate polarizations when thick foils are used.

  15. 5 MeV Mott Polarimeter Development at Jefferson Lab

    SciTech Connect

    Price, J. S.; Sinclair, C. K.; Cardman, L. S.; Haanskneccht, J.; Mack, D. J.; Piot, P.; Assamagan, K. A.; Grames, J.

    1997-01-01

    Low energy (E{sub k}=100 keV) Mott scattering polarimeters are ill- suited to support operations foreseen for the polarized electron injector at Jefferson Lab. One solution is to measure the polarization at 5 MeV where multiple and plural scattering are unimportant and precision beam monitoring is straightforward. The higher injector beam current offsets the lower cross-sections. Recent improvements in the CEBAF injector polarimeter scattering chamber have improved signal to noise.

  16. Photoheat-induced Schottky nanojunction and indirect Mott transition in VO2: photocurrent analysis

    NASA Astrophysics Data System (ADS)

    Kim, Hyun-Tak; Kim, Minjung; Sohn, Ahrum; Slusar, Tetiana; Seo, Giwan; Cheong, Hyeonsik; Kim, Dong-Wook

    2016-03-01

    In order to elucidate a mechanism of the insulator-to-metal transition (IMT) for a Mott insulator VO2 (3d 1), we present Schottky nanojunctions and the structural phase transition (SPT) by simultaneous nanolevel measurements of photocurrent and Raman scattering in microlevel devices. The Schottky nanojunction with the monoclinic metallic phase between the monoclinic insulating phases is formed by the photoheat-induced IMT not accompanied with the SPT. The temperature dependence of the Schottky junction reveals that the Mott insulator has an electronic structure of an indirect subband between the main Hubbard d bands. The IMT as reverse process of the Mott transition occurs by temperature-induced excitation of bound charges in the indirect semiconductor band, most likely formed by impurities such as oxygen deficiency. The metal band (3d 1) for the Mott insulator is screened (trapped) by the indirect band (impurities).

  17. Fate of Spinons at the Mott Point

    NASA Astrophysics Data System (ADS)

    Lee, Tsung-Han; Florens, Serge; Dobrosavljević, Vladimir

    2016-09-01

    Gapless spin liquids have recently been observed in several frustrated Mott insulators, with elementary spin excitations—"spinons"—reminiscent of degenerate Fermi systems. However, their precise role at the Mott point, where charge fluctuations begin to proliferate, remains controversial and ill understood. Here we present the simplest theoretical framework that treats the dynamics of emergent spin and charge excitations on the same footing, providing a new physical picture of the Mott metal-to-insulator transition at half filing. We identify a generic orthogonality mechanism leading to strong damping of spinons, arising as soon as the Mott gap closes. Our results indicate that spinons should not play a significant role within the high-temperature quantum critical regime above the Mott point—in striking agreement with all available experiments.

  18. Influence of spinons fluctuations near the spin liquid Mott transition

    NASA Astrophysics Data System (ADS)

    Lee, Tsung-Han; Florens, Serge; Dobrosavljevic, Vladimir

    We investigate the metal to Mott-insulator transition (MIT) in the Hubbard-Heisenberg model using the slave-rotor technique, which allows to combine for the first time the dynamical mean field theory (DMFT) with the Resonating Valence Bond (RVB) approach. In the spin-liquid phase at large Coulomb repulsion, the system shows a RVB transition from a trivial paramagnetic Mott insulator towards a low temperature insulating state with long lived spinons, as seen by the emergence of a linear specific heat. This quenching of the entropy in the spin liquid phase provides strong modifications in the shape of the standard DMFT phase diagram for the MIT occurring at intermediate values of the Coulomb repulsion. We find that the RVB transition happens concomitantly with the first order MIT lines at low temperature. This implies that the Mott insulator always accommodates a spinon Fermi surface, even in the coexistence regime of the MIT, and that the metallic state always stays a Fermi-liquid as it rejects the presence of free spinons, due to their strong scattering onto the holons.

  19. Mott transitions in the periodic Anderson model.

    PubMed

    Logan, David E; Galpin, Martin R; Mannouch, Jonathan

    2016-11-16

    The periodic Anderson model (PAM) is studied within the framework of dynamical mean-field theory, with particular emphasis on the interaction-driven Mott transition it contains, and on resultant Mott insulators of both Mott-Hubbard and charge-transfer type. The form of the PAM phase diagram is first deduced on general grounds using two exact results, over the full range of model parameters and including metallic, Mott, Kondo and band insulator phases. The effective low-energy model which describes the PAM in the vicinity of a Mott transition is then shown to be a one-band Hubbard model, with effective hoppings that are not in general solely nearest neighbour, but decay exponentially with distance. This mapping is shown to have a range of implications for the physics of the problem, from phase boundaries to single-particle dynamics; all of which are confirmed and supplemented by NRG calculations. Finally we consider the locally degenerate, non-Fermi liquid Mott insulator, to describe which requires a two-self-energy description. This is shown to yield a number of exact results for the associated local moment, charge, and interaction-renormalised levels, together with a generalisation of Luttinger's theorem to the Mott insulator.

  20. Mott transitions in the periodic Anderson model

    NASA Astrophysics Data System (ADS)

    Logan, David E.; Galpin, Martin R.; Mannouch, Jonathan

    2016-11-01

    The periodic Anderson model (PAM) is studied within the framework of dynamical mean-field theory, with particular emphasis on the interaction-driven Mott transition it contains, and on resultant Mott insulators of both Mott-Hubbard and charge-transfer type. The form of the PAM phase diagram is first deduced on general grounds using two exact results, over the full range of model parameters and including metallic, Mott, Kondo and band insulator phases. The effective low-energy model which describes the PAM in the vicinity of a Mott transition is then shown to be a one-band Hubbard model, with effective hoppings that are not in general solely nearest neighbour, but decay exponentially with distance. This mapping is shown to have a range of implications for the physics of the problem, from phase boundaries to single-particle dynamics; all of which are confirmed and supplemented by NRG calculations. Finally we consider the locally degenerate, non-Fermi liquid Mott insulator, to describe which requires a two-self-energy description. This is shown to yield a number of exact results for the associated local moment, charge, and interaction-renormalised levels, together with a generalisation of Luttinger’s theorem to the Mott insulator.

  1. Mott transitions in the periodic Anderson model.

    PubMed

    Logan, David E; Galpin, Martin R; Mannouch, Jonathan

    2016-11-16

    The periodic Anderson model (PAM) is studied within the framework of dynamical mean-field theory, with particular emphasis on the interaction-driven Mott transition it contains, and on resultant Mott insulators of both Mott-Hubbard and charge-transfer type. The form of the PAM phase diagram is first deduced on general grounds using two exact results, over the full range of model parameters and including metallic, Mott, Kondo and band insulator phases. The effective low-energy model which describes the PAM in the vicinity of a Mott transition is then shown to be a one-band Hubbard model, with effective hoppings that are not in general solely nearest neighbour, but decay exponentially with distance. This mapping is shown to have a range of implications for the physics of the problem, from phase boundaries to single-particle dynamics; all of which are confirmed and supplemented by NRG calculations. Finally we consider the locally degenerate, non-Fermi liquid Mott insulator, to describe which requires a two-self-energy description. This is shown to yield a number of exact results for the associated local moment, charge, and interaction-renormalised levels, together with a generalisation of Luttinger's theorem to the Mott insulator. PMID:27618214

  2. Hallmarks of the Mott-metal crossover in the hole-doped pseudospin-1/2 Mott insulator Sr2IrO4.

    PubMed

    Cao, Yue; Wang, Qiang; Waugh, Justin A; Reber, Theodore J; Li, Haoxiang; Zhou, Xiaoqing; Parham, Stephen; Park, S-R; Plumb, Nicholas C; Rotenberg, Eli; Bostwick, Aaron; Denlinger, Jonathan D; Qi, Tongfei; Hermele, Michael A; Cao, Gang; Dessau, Daniel S

    2016-04-22

    The physics of doped Mott insulators remains controversial after decades of active research, hindered by the interplay among competing orders and fluctuations. It is thus highly desired to distinguish the intrinsic characters of the Mott-metal crossover from those of other origins. Here we investigate the evolution of electronic structure and dynamics of the hole-doped pseudospin-1/2 Mott insulator Sr2IrO4. The effective hole doping is achieved by replacing Ir with Rh atoms, with the chemical potential immediately jumping to or near the top of the lower Hubbard band. The doped iridates exhibit multiple iconic low-energy features previously observed in doped cuprates-pseudogaps, Fermi arcs and marginal-Fermi-liquid-like electronic scattering rates. We suggest these signatures are most likely an integral part of the material's proximity to the Mott state, rather than from many of the most claimed mechanisms, including preformed electron pairing, quantum criticality or density-wave formation.

  3. Hallmarks of the Mott-metal crossover in the hole-doped pseudospin-1/2 Mott insulator Sr2IrO4

    NASA Astrophysics Data System (ADS)

    Cao, Yue; Wang, Qiang; Waugh, Justin A.; Reber, Theodore J.; Li, Haoxiang; Zhou, Xiaoqing; Parham, Stephen; Park, S.-R.; Plumb, Nicholas C.; Rotenberg, Eli; Bostwick, Aaron; Denlinger, Jonathan D.; Qi, Tongfei; Hermele, Michael A.; Cao, Gang; Dessau, Daniel S.

    2016-04-01

    The physics of doped Mott insulators remains controversial after decades of active research, hindered by the interplay among competing orders and fluctuations. It is thus highly desired to distinguish the intrinsic characters of the Mott-metal crossover from those of other origins. Here we investigate the evolution of electronic structure and dynamics of the hole-doped pseudospin-1/2 Mott insulator Sr2IrO4. The effective hole doping is achieved by replacing Ir with Rh atoms, with the chemical potential immediately jumping to or near the top of the lower Hubbard band. The doped iridates exhibit multiple iconic low-energy features previously observed in doped cuprates--pseudogaps, Fermi arcs and marginal-Fermi-liquid-like electronic scattering rates. We suggest these signatures are most likely an integral part of the material's proximity to the Mott state, rather than from many of the most claimed mechanisms, including preformed electron pairing, quantum criticality or density-wave formation.

  4. Hallmarks of the Mott-metal crossover in the hole-doped pseudospin-1/2 Mott insulator Sr2IrO4.

    PubMed

    Cao, Yue; Wang, Qiang; Waugh, Justin A; Reber, Theodore J; Li, Haoxiang; Zhou, Xiaoqing; Parham, Stephen; Park, S-R; Plumb, Nicholas C; Rotenberg, Eli; Bostwick, Aaron; Denlinger, Jonathan D; Qi, Tongfei; Hermele, Michael A; Cao, Gang; Dessau, Daniel S

    2016-01-01

    The physics of doped Mott insulators remains controversial after decades of active research, hindered by the interplay among competing orders and fluctuations. It is thus highly desired to distinguish the intrinsic characters of the Mott-metal crossover from those of other origins. Here we investigate the evolution of electronic structure and dynamics of the hole-doped pseudospin-1/2 Mott insulator Sr2IrO4. The effective hole doping is achieved by replacing Ir with Rh atoms, with the chemical potential immediately jumping to or near the top of the lower Hubbard band. The doped iridates exhibit multiple iconic low-energy features previously observed in doped cuprates-pseudogaps, Fermi arcs and marginal-Fermi-liquid-like electronic scattering rates. We suggest these signatures are most likely an integral part of the material's proximity to the Mott state, rather than from many of the most claimed mechanisms, including preformed electron pairing, quantum criticality or density-wave formation. PMID:27102065

  5. Hallmarks of the Mott-metal crossover in the hole-doped pseudospin-1/2 Mott insulator Sr2IrO4

    PubMed Central

    Cao, Yue; Wang, Qiang; Waugh, Justin A.; Reber, Theodore J.; Li, Haoxiang; Zhou, Xiaoqing; Parham, Stephen; Park, S.-R.; Plumb, Nicholas C.; Rotenberg, Eli; Bostwick, Aaron; Denlinger, Jonathan D.; Qi, Tongfei; Hermele, Michael A.; Cao, Gang; Dessau, Daniel S.

    2016-01-01

    The physics of doped Mott insulators remains controversial after decades of active research, hindered by the interplay among competing orders and fluctuations. It is thus highly desired to distinguish the intrinsic characters of the Mott-metal crossover from those of other origins. Here we investigate the evolution of electronic structure and dynamics of the hole-doped pseudospin-1/2 Mott insulator Sr2IrO4. The effective hole doping is achieved by replacing Ir with Rh atoms, with the chemical potential immediately jumping to or near the top of the lower Hubbard band. The doped iridates exhibit multiple iconic low-energy features previously observed in doped cuprates—pseudogaps, Fermi arcs and marginal-Fermi-liquid-like electronic scattering rates. We suggest these signatures are most likely an integral part of the material's proximity to the Mott state, rather than from many of the most claimed mechanisms, including preformed electron pairing, quantum criticality or density-wave formation. PMID:27102065

  6. Constraints on topological order in mott insulators.

    PubMed

    Zaletel, Michael P; Vishwanath, Ashvin

    2015-02-20

    We point out certain symmetry induced constraints on topological order in Mott insulators (quantum magnets with an odd number of spin 1/2 moments per unit cell). We show, for example, that the double-semion topological order is incompatible with time reversal and translation symmetry in Mott insulators. This sharpens the Hastings-Oshikawa-Lieb-Schultz-Mattis theorem for 2D quantum magnets, which guarantees that a fully symmetric gapped Mott insulator must be topologically ordered, but is silent about which topological order is permitted. Our result applies to the kagome lattice quantum antiferromagnet, where recent numerical calculations of the entanglement entropy indicate a ground state compatible with either toric code or double-semion topological order. Our result rules out the latter possibility.

  7. Constraints on topological order in mott insulators.

    PubMed

    Zaletel, Michael P; Vishwanath, Ashvin

    2015-02-20

    We point out certain symmetry induced constraints on topological order in Mott insulators (quantum magnets with an odd number of spin 1/2 moments per unit cell). We show, for example, that the double-semion topological order is incompatible with time reversal and translation symmetry in Mott insulators. This sharpens the Hastings-Oshikawa-Lieb-Schultz-Mattis theorem for 2D quantum magnets, which guarantees that a fully symmetric gapped Mott insulator must be topologically ordered, but is silent about which topological order is permitted. Our result applies to the kagome lattice quantum antiferromagnet, where recent numerical calculations of the entanglement entropy indicate a ground state compatible with either toric code or double-semion topological order. Our result rules out the latter possibility. PMID:25763971

  8. Holography and Mottness: A Discrete Marriage

    NASA Astrophysics Data System (ADS)

    Phillips, Philip

    2012-02-01

    Gauge-gravity duality has allowed us to solve the physics of certain strongly coupled quantum mechanical systems using gravity. I will show how a space-time consisting of a charged black hole and a bulk Pauli coupling corresponds to a boundary theory with a dynamically generated gap (with no obvious symmetry breaking) and a massive rearrangement of the spectral weight as in classic Mott systems such as VO2. In this holographic set-up, the gap opens only when discrete scale invariance is present. This raises the possibility that the elusive symmetry that might be broken in Mott insulators, in general, might pertain to scale invariance. The relevance of this claim to recent theories of Mott systems that possess massless charged bosons is explored.

  9. Universality class of the mott transition.

    PubMed

    Abdel-Jawad, M; Kato, R; Watanabe, I; Tajima, N; Ishii, Y

    2015-03-13

    Pressure dependence of the conductivity and thermoelectric power is measured through the Mott transition in the layer organic conductor EtMe_{3}P[Pd(dmit)_{2}]_{2}. The critical behavior of the thermoelectric effect provides a clear and objective determination of the Mott-Hubbard transition during the isothermal pressure sweep. Above the critical end point, the metal-insulator crossing, determined by the thermoelectric effect minimum value, is not found to coincide with the maximum of the derivative of the conductivity as a function of pressure. We show that the critical exponents of the Mott-Hubbard transition fall within the Ising universality class regardless of the dimensionality of the system. PMID:25815951

  10. Quantum and classical solutions for statically screened two-dimensional Wannier-Mott excitons

    SciTech Connect

    Makowski, Adam J.

    2011-08-15

    Quantum solutions and classical orbits are discussed for statically screened Wannier-Mott excitons for two closely related potentials: the Stern-Howard potential and a suggested simple focusing one. Bound states and exact ''quantized'' values of screening are obtained as well. For the suggested potential, the scattering matrix, the Regge poles, and the transmission coefficient are calculated exactly. We argue that the simple potential can be utilized in applications instead of the Stern-Howard potential, which is difficult to handle.

  11. Electronic reconstruction of doped Mott insulator heterojunctions

    NASA Astrophysics Data System (ADS)

    Charlebois, M.; Hassan, S. R.; Karan, R.; Dion, M.; Senechal, D.; Tremblay, A.-M. S.

    2012-02-01

    Correlated electron heterostructures became a possible alternative when thin-film deposition techniques achieved structures with a sharp interface transition [1]. Soon thereafter, Okamoto & Millis introduced the concept of ``electronic reconstruction'' [2]. We study here the electronic reconstruction of doped Mott insulator heterostructures based on a Cluster Dynamical Mean Field Theory (CDMFT) calculations of the Hubbard model in the limit where electrostatic energy dominates over the kinetic energy associated with transport across layers. The grand potential of individual layers is first computed within CDMFT and then the electrostatic potential energy is taken into account in the Hartree approximation. The charge reconstruction in an ensemble of stacked planes of different nature can lead to a distribution of electron charge and to transport properties that are unique to doped-Mott insulators.[4pt] [1] J. Mannhart, D. G. Schlom, Science 327, 1607 (2010).[0pt] [2] S. Okamoto and A. J. Millis, Nature 428, 630 (2004).

  12. DYNAMICAL RESPONSE OF QUASI ID MOTT INSULATORS.

    SciTech Connect

    ESSLER,F.H.L.TSVELIK,A.M.

    2004-01-14

    At low energies certain one dimensional Mott insulators can be described in terms of an exactly solvable quantum field theory, the U(1) Thirring model. Using exact results derived from integrability we determine dynamical properties like the frequency dependent optical conductivity and the single-particle Green's function. We discuss the effects of a small temperature and the effects on interchain tunneling in a model of infinitely many weakly coupled chains.

  13. Ferroelectric control of a Mott insulator.

    PubMed

    Yamada, Hiroyuki; Marinova, Maya; Altuntas, Philippe; Crassous, Arnaud; Bégon-Lours, Laura; Fusil, Stéphane; Jacquet, Eric; Garcia, Vincent; Bouzehouane, Karim; Gloter, Alexandre; Villegas, Javier E; Barthélémy, Agnès; Bibes, Manuel

    2013-10-03

    The electric field control of functional properties is an important goal in oxide-based electronics. To endow devices with memory, ferroelectric gating is interesting, but usually weak compared to volatile electrolyte gating. Here, we report a very large ferroelectric field-effect in perovskite heterostructures combining the Mott insulator CaMnO3 and the ferroelectric BiFeO3 in its "supertetragonal" phase. Upon polarization reversal of the BiFeO3 gate, the CaMnO3 channel resistance shows a fourfold variation around room temperature, and a tenfold change at ~200 K. This is accompanied by a carrier density modulation exceeding one order of magnitude. We have analyzed the results for various CaMnO3 thicknesses and explain them by the electrostatic doping of the CaMnO3 layer and the presence of a fixed dipole at the CaMnO3/BiFeO3 interface. Our results suggest the relevance of ferroelectric gates to control orbital- or spin-ordered phases, ubiquitous in Mott systems, and pave the way toward efficient Mott-tronics devices.

  14. Ferroelectric control of a Mott insulator

    PubMed Central

    Yamada, Hiroyuki; Marinova, Maya; Altuntas, Philippe; Crassous, Arnaud; Bégon-Lours, Laura; Fusil, Stéphane; Jacquet, Eric; Garcia, Vincent; Bouzehouane, Karim; Gloter, Alexandre; Villegas, Javier E.; Barthélémy, Agnès; Bibes, Manuel

    2013-01-01

    The electric field control of functional properties is an important goal in oxide-based electronics. To endow devices with memory, ferroelectric gating is interesting, but usually weak compared to volatile electrolyte gating. Here, we report a very large ferroelectric field-effect in perovskite heterostructures combining the Mott insulator CaMnO3 and the ferroelectric BiFeO3 in its “supertetragonal” phase. Upon polarization reversal of the BiFeO3 gate, the CaMnO3 channel resistance shows a fourfold variation around room temperature, and a tenfold change at ~200 K. This is accompanied by a carrier density modulation exceeding one order of magnitude. We have analyzed the results for various CaMnO3 thicknesses and explain them by the electrostatic doping of the CaMnO3 layer and the presence of a fixed dipole at the CaMnO3/BiFeO3 interface. Our results suggest the relevance of ferroelectric gates to control orbital- or spin-ordered phases, ubiquitous in Mott systems, and pave the way toward efficient Mott-tronics devices. PMID:24089020

  15. Dimensional decoupling at continuous quantum critical Mott transitions

    NASA Astrophysics Data System (ADS)

    Zou, Liujun; Senthil, T.

    2016-09-01

    For continuous Mott metal-insulator transitions in layered two-dimensional systems, we demonstrate the phenomenon of dimensional decoupling: the system behaves as a three-dimensional metal in the Fermi-liquid side but as a stack of decoupled two-dimensional layers in the Mott insulator. We show that the dimensional decoupling happens at the Mott quantum critical point itself. We derive the temperature dependence of the interlayer electric conductivity in various crossover regimes near such a continuous Mott transition, and discuss experimental implications.

  16. Quantum phase transitions and local magnetism in Mott insulators: A local probe investigation using muons, neutrons, and photons

    NASA Astrophysics Data System (ADS)

    Frandsen, Benjamin A.

    Mott insulators are materials in which strong correlations among the electrons induce an unconventional insulating state. Rich interplay between the structural, magnetic, and electronic degrees of freedom resulting from the electron correlation can lead to unusual complexity of Mott materials on the atomic scale, such as microscopically heterogeneous phases or local structural correlations that deviate significantly from the average structure. Such behavior must be studied by suitable experimental techniques, i.e. "local probes", that are sensitive to this local behavior rather than just the bulk, average properties. In this thesis, I will present results from our studies of multiple families of Mott insulators using two such local probes: muon spin relaxation (muSR), a probe of local magnetism; and pair distribution function (PDF) analysis of x-ray and neutron total scattering, a probe of local atomic structure. In addition, I will present the development of magnetic pair distribution function analysis, a novel method for studying local magnetic correlations that is highly complementary to the muSR and atomic PDF techniques. We used muSR to study the phase transition from Mott insulator to metal in two archetypal Mott insulating systems: RENiO3 (RE = rare earth element) and V2O3. In both of these systems, the Mott insulating state can be suppressed by tuning a nonthermal parameter, resulting in a "quantum" phase transition at zero temperature from the Mott insulating state to a metallic state. In RENiO3, this occurs through variation of the rare-earth element in the chemical composition; in V 2O3, through the application of hydrostatic pressure. Our results show that the metallic and Mott insulating states unexpectedly coexist in phase-separated regions across a large portion of parameter space near the Mott quantum phase transition and that the magnitude of the ordered antiferromagnetic moment remains constant across the phase diagram until it is abruptly

  17. Singlet Mott state simulating the bosonic Laughlin wave function

    NASA Astrophysics Data System (ADS)

    Lian, Biao; Zhang, Shoucheng

    2014-01-01

    We study properties of a class of spin-singlet Mott states for arbitrary spin S bosons on a lattice, with particle number per cite n =S/l+1, where l is a positive integer. We show that such a singlet Mott state can be mapped to a bosonic Laughlin wave function on a sphere with a finite number of particles at filling ν =1/2l. Spin, particle, and hole excitations in the Mott state are discussed, among which the hole excitation can be mapped to the quasihole of the bosonic Laughlin wave function. We show that this singlet Mott state can be realized in a cold-atom system on an optical lattice and can be identified using Bragg spectroscopy and Stern-Gerlach techniques. This class of singlet Mott states may be generalized to map to bosonic Laughlin states with filling ν =q/2l.

  18. Singlet Mott State Simulating the Bosonic Laughlin Wave Function

    NASA Astrophysics Data System (ADS)

    Lian, Biao; Zhang, Shou-Cheng

    2014-03-01

    We study properties of a class of spin singlet Mott states for arbitrary spin S bosons on a lattice, with particle number per cite n = S / l + 1 , where l is a positive integer. We show that such a singlet Mott state can be mapped to a bosonic Laughlin wave function on the sphere with a finite number of particles at filling ν = 1 / 2 l . Bosonic spinons, particle and hole excitations in the Mott state are discussed, among which the hole excitation can be mapped to the quasi-hole of the bosonic Laughlin wave function. We show that this singlet Mott state can be realized in a cold atom system on optical lattice, and can be identified using Bragg spectroscopy and Stern-Gerlach techniques. This class of singlet Mott states may be generalized to simulate bosonic Laughlin states with filling ν = q / 2 l .

  19. A low-voltage retarding-field Mott polarimeter for photocathode characterization

    NASA Astrophysics Data System (ADS)

    McCarter, J. L.; Stutzman, M. L.; Trantham, K. W.; Anderson, T. G.; Cook, A. M.; Gay, T. J.

    2010-06-01

    Nuclear physics experiments at Thomas Jefferson National Accelerator Facility's CEBAF rely on high polarization electron beams. We describe a recently commissioned system for prequalifying and studying photocathodes for CEBAF with a load-locked, low-voltage polarized electron source coupled to a compact retarding-field Mott polarimeter. The polarimeter uses simplified electrode structures and operates from 5 to 30 kV. The effective Sherman function for this device has been calibrated by comparison with the CEBAF 5 MeV Mott polarimeter. For elastic scattering from a thick gold target at 20 keV, the effective Sherman function is 0.201(5). Its maximum efficiency at 20 keV, defined as the detected count rate divided by the incident particle current, is 5.4(2)×10 -4, yielding a figure-of-merit, or analyzing power squared times efficiency, of 1.0(1)×10 -5. The operating parameters of this new polarimeter design are compared to previously published data for other compact Mott polarimeters of the retarding-field type.

  20. A low-voltage retarding-field Mott polarimeter for photocathode characterization

    SciTech Connect

    McCarter, J. L.; Stutzman, M. L.; Trantham, K. W.; Anderson, T. G.; Cook, A. M.; Gay, T. J.

    2010-02-26

    Nuclear physics experiments at Thomas Jefferson National Accelerator Facility's CEBAF rely on high polarization electron beams. We describe a recently commissioned system for prequalifying and studying photocathodes for CEBAF with a load-locked, low-voltage polarized electron source coupled to a compact retarding-field Mott polarimeter. The polarimeter uses simplified electrode structures and operates from 5 to 30 kV. The effective Sherman function for this device has been calibrated by comparison with the CEBAF 5 MeV Mott polarimeter. For elastic scattering from a thick gold target at 20 keV, the effective Sherman function is 0.201(5). Its maximum efficiency at 20 keV, defined as the detected count rate divided by the incident particle current, is 5.4(2)×10-4, yielding a figure-of-merit, or analyzing power squared times efficiency, of 1.0(1)×10-5. The operating parameters of this new polarimeter design are compared to previously published data for other compact Mott polarimeters of the retarding-field type.

  1. MOTT FOUNDATION PROJECTS MOTT PROGRAM--FLINT PUBLIC SCHOOLS, SUMMARY REPORTS JULY 1, 1964 TO JUNE 30, 1965.

    ERIC Educational Resources Information Center

    BRIGGS, LARRY; AND OTHERS

    ONE-PAGE REPORTS ARE PRESENTED, SUMMARIZING EACH OF THE PROJECTS IN THE MOTT PROGRAM FOR THE FLINT PUBLIC SCHOOLS--WORKSHOPS AND VISITATIONS, ADULT EDUCATION, GRADUATE TRAINING, YOUTH PROGRAMS, THE MOTT CAMP, RECREATION, A BETTER TOMORROW FOR THE URBAN CHILD, THE PERSONALIZED CURRICULUM PROGRAM, MEDICAL-DENTAL HEALTH, INTERUNIVERSITY CLINICAL…

  2. Dual vortex theory of doped Mott insulators

    SciTech Connect

    Balents, Leon; Sachdev, Subir

    2007-11-15

    We present a general framework for describing the quantum phases obtained by doping paramagnetic Mott insulators on the square lattice. The undoped insulators are efficiently characterized by the projective transformations of various fields under the square lattice space group (the PSG). We show that the PSG also imposes powerful constraints on the doped system, and on the effective action for the vortex and Bogoliubov quasiparticle excitations of superconducting states. This action can also be extended across transitions to supersolid or insulating states at non-zero doping. For the case of a valence bond solid (VBS) insulator, we show that the doped system has the same PSG as that of elementary bosons with density equal to the density of electron Cooper pairs. We also discuss aspects of the action for a d-wave superconductor obtained by doping a 'staggered-flux' spin liquid state.

  3. Quench from Mott Insulator to Superfluid

    SciTech Connect

    Zurek, Wojciech H.; Dziarmaga, Jacek; Tylutki, Marek

    2012-06-01

    We study a linear ramp of the nearest-neighbor tunneling rate in the Bose-Hubbard model driving the system from the Mott insulator state into the superfluid phase. We employ the truncated Wigner approximation to simulate linear quenches of a uniform system in 1...3 dimensions, and in a harmonic trap in 3 dimensions. In all these setups the excitation energy decays like one over third root of the quench time. The -1/3 scaling is explained by an impulse-adiabatic approximation - a variant of the Kibble-Zurek mechanism - describing a crossover from non-adiabatic to adiabatic evolution when the system begins to keep pace with the increasing tunneling rate.

  4. Bose and Mott glass phases in dimerized quantum antiferromagnets

    NASA Astrophysics Data System (ADS)

    Thomson, S. J.; Krüger, F.

    2015-11-01

    We examine the effects of disorder on dimerized quantum antiferromagnets in a magnetic field, using the mapping to a lattice gas of hard-core bosons with finite-range interactions. Combining a strong-coupling expansion, the replica method, and a one-loop renormalization-group analysis, we investigate the nature of the glass phases formed. We find that away from the tips of the Mott lobes, the transition is from a Mott insulator to a compressible Bose glass, however the compressibility at the tips is strongly suppressed. We identify this finding with the presence of a rare Mott glass phase and demonstrate that the inclusion of replica symmetry breaking is vital to correctly describe the glassy phases. This result suggests that the formation of Bose and Mott glass phases is not simply a weak localization phenomenon but is indicative of much richer physics. We discuss our results in the context of both ultracold atomic gases and spin-dimer materials.

  5. Precision measurements on a tunable Mott insulator of ultracold atoms.

    PubMed

    Mark, M J; Haller, E; Lauber, K; Danzl, J G; Daley, A J; Nägerl, H-C

    2011-10-21

    We perform precision measurements on a Mott-insulator quantum state of ultracold atoms with tunable interactions. We probe the dependence of the superfluid-to-Mott-insulator transition on the interaction strength and explore the limits of the standard Bose-Hubbard model description. By tuning the on-site interaction energies to values comparable to the interband separation, we are able to quantitatively measure number-dependent shifts in the excitation spectrum caused by effective multibody interactions. PMID:22107531

  6. Unusual Mott transition in multiferroic PbCrO3

    PubMed Central

    Wang, Shanmin; Zhu, Jinlong; Zhang, Yi; Yu, Xiaohui; Zhang, Jianzhong; Wang, Wendan; Bai, Ligang; Qian, Jiang; Yin, Liang; Sullivan, Neil S.; Jin, Changqing; He, Duanwei; Xu, Jian; Zhao, Yusheng

    2015-01-01

    The Mott insulator in correlated electron systems arises from classical Coulomb repulsion between carriers to provide a powerful force for electron localization. Turning such an insulator into a metal, the so-called Mott transition, is commonly achieved by “bandwidth” control or “band filling.” However, both mechanisms deviate from the original concept of Mott, which attributes such a transition to the screening of Coulomb potential and associated lattice contraction. Here, we report a pressure-induced isostructural Mott transition in cubic perovskite PbCrO3. At the transition pressure of ∼3 GPa, PbCrO3 exhibits significant collapse in both lattice volume and Coulomb potential. Concurrent with the collapse, it transforms from a hybrid multiferroic insulator to a metal. For the first time to our knowledge, these findings validate the scenario conceived by Mott. Close to the Mott criticality at ∼300 K, fluctuations of the lattice and charge give rise to elastic anomalies and Laudau critical behaviors resembling the classic liquid–gas transition. The anomalously large lattice volume and Coulomb potential in the low-pressure insulating phase are largely associated with the ferroelectric distortion, which is substantially suppressed at high pressures, leading to the first-order phase transition without symmetry breaking. PMID:26604314

  7. Unusual Mott transition in multiferroic PbCrO 3

    DOE PAGESBeta

    Wang, Shanmin; Zhu, Jinlong; Zhang, Yi; Yu, Xiaohui; Zhang, Jianzhong; Wang, Wendan; Bai, Ligang; Qian, Jiang; Yin, Liang; Sullivan, Neil S.; et al

    2015-11-24

    The Mott insulator in correlated electron systems arises from classical Coulomb repulsion between carriers to provide a powerful force for electron localization. When turning such an insulator into a metal, the so-called Mott transition, is commonly achieved by "bandwidth" control or "band filling." However, both mechanisms deviate from the original concept of Mott, which attributes such a transition to the screening of Coulomb potential and associated lattice contraction. We report a pressure-induced isostructural Mott transition in cubic perovskite PbCrO3. At the transition pressure of similar to 3 GPa, PbCrO3 exhibits significant collapse in both lattice volume and Coulomb potential. Concurrentmore » with the collapse, it transforms from a hybrid multiferroic insulator to a metal. For the first time to our knowledge, these findings validate the scenario conceived by Mott. Close to the Mott criticality at similar to 300 K, fluctuations of the lattice and charge give rise to elastic anomalies and Laudau critical behaviors resembling the classic liquid-gas transition. Moreover, the anomalously large lattice volume and Coulomb potential in the low-pressure insulating phase are largely associated with the ferroelectric distortion, which is substantially suppressed at high pressures, leading to the first-order phase transition without symmetry breaking.« less

  8. Unusual Mott transition in multiferroic PbCrO3.

    PubMed

    Wang, Shanmin; Zhu, Jinlong; Zhang, Yi; Yu, Xiaohui; Zhang, Jianzhong; Wang, Wendan; Bai, Ligang; Qian, Jiang; Yin, Liang; Sullivan, Neil S; Jin, Changqing; He, Duanwei; Xu, Jian; Zhao, Yusheng

    2015-12-15

    The Mott insulator in correlated electron systems arises from classical Coulomb repulsion between carriers to provide a powerful force for electron localization. Turning such an insulator into a metal, the so-called Mott transition, is commonly achieved by "bandwidth" control or "band filling." However, both mechanisms deviate from the original concept of Mott, which attributes such a transition to the screening of Coulomb potential and associated lattice contraction. Here, we report a pressure-induced isostructural Mott transition in cubic perovskite PbCrO3. At the transition pressure of ∼3 GPa, PbCrO3 exhibits significant collapse in both lattice volume and Coulomb potential. Concurrent with the collapse, it transforms from a hybrid multiferroic insulator to a metal. For the first time to our knowledge, these findings validate the scenario conceived by Mott. Close to the Mott criticality at ∼300 K, fluctuations of the lattice and charge give rise to elastic anomalies and Laudau critical behaviors resembling the classic liquid-gas transition. The anomalously large lattice volume and Coulomb potential in the low-pressure insulating phase are largely associated with the ferroelectric distortion, which is substantially suppressed at high pressures, leading to the first-order phase transition without symmetry breaking. PMID:26604314

  9. Suppression of rectification at metal-Mott insulator interfaces

    NASA Astrophysics Data System (ADS)

    Yonemitsu, Kenji; Maeshima, Nobuya; Hasegawa, Tatsuo

    2007-12-01

    Charge transport through metal-Mott insulator interfaces is studied and compared with that through metal-band-insulator interfaces. For band insulators, rectification has been known to occur owing to a Schottky barrier, which is produced by the work-function difference. For Mott insulators, however, qualitatively different current-voltage characteristics are obtained. Theoretically, we use the one-dimensional Hubbard model for a Mott insulator and attach to it the tight-binding model for metallic electrodes. A Schottky barrier is introduced by a solution to the Poisson equation with a simplified density-potential relation. The current density is calculated by solving the time-dependent Schrödinger equation. We mainly use the time-dependent Hartree-Fock approximation and also use exact many-electron wave functions on small systems for comparison. Rectification is found to be strongly suppressed even for large work-function differences. We show its close relationship with the fact that field-effect injections into one-dimensional Mott insulators are ambipolar. Experimentally, we fabricated asymmetric contacts on top of single crystals of quasi-one-dimensional organic Mott and band insulators. Rectification is strongly suppressed at an interface between metallic magnesium and Mott-insulating (BEDT-TTF)(F2TCNQ) [ BEDT-TTF=bis(ethylenedithio)tetrathiafulvalene ; F2TCNQ=2,5-difluorotetracyanoquinodimethane ].

  10. A scalable neuristor built with Mott memristors.

    PubMed

    Pickett, Matthew D; Medeiros-Ribeiro, Gilberto; Williams, R Stanley

    2013-02-01

    The Hodgkin-Huxley model for action potential generation in biological axons is central for understanding the computational capability of the nervous system and emulating its functionality. Owing to the historical success of silicon complementary metal-oxide-semiconductors, spike-based computing is primarily confined to software simulations and specialized analogue metal-oxide-semiconductor field-effect transistor circuits. However, there is interest in constructing physical systems that emulate biological functionality more directly, with the goal of improving efficiency and scale. The neuristor was proposed as an electronic device with properties similar to the Hodgkin-Huxley axon, but previous implementations were not scalable. Here we demonstrate a neuristor built using two nanoscale Mott memristors, dynamical devices that exhibit transient memory and negative differential resistance arising from an insulating-to-conducting phase transition driven by Joule heating. This neuristor exhibits the important neural functions of all-or-nothing spiking with signal gain and diverse periodic spiking, using materials and structures that are amenable to extremely high-density integration with or without silicon transistors. PMID:23241533

  11. A scalable neuristor built with Mott memristors

    NASA Astrophysics Data System (ADS)

    Pickett, Matthew D.; Medeiros-Ribeiro, Gilberto; Williams, R. Stanley

    2013-02-01

    The Hodgkin-Huxley model for action potential generation in biological axons is central for understanding the computational capability of the nervous system and emulating its functionality. Owing to the historical success of silicon complementary metal-oxide-semiconductors, spike-based computing is primarily confined to software simulations and specialized analogue metal-oxide-semiconductor field-effect transistor circuits. However, there is interest in constructing physical systems that emulate biological functionality more directly, with the goal of improving efficiency and scale. The neuristor was proposed as an electronic device with properties similar to the Hodgkin-Huxley axon, but previous implementations were not scalable. Here we demonstrate a neuristor built using two nanoscale Mott memristors, dynamical devices that exhibit transient memory and negative differential resistance arising from an insulating-to-conducting phase transition driven by Joule heating. This neuristor exhibits the important neural functions of all-or-nothing spiking with signal gain and diverse periodic spiking, using materials and structures that are amenable to extremely high-density integration with or without silicon transistors.

  12. Nonequilibrium gap collapse near a first-order Mott transition

    NASA Astrophysics Data System (ADS)

    Sandri, Matteo; Fabrizio, Michele

    2015-03-01

    We study the nonequilibrium dynamics of a simple model for V2O3 that consists of a quarter-filled Hubbard model for two orbitals that are split by a weak crystal field. Peculiarities of this model are (1) a Mott insulator whose gap corresponds to transferring an electron from the occupied lower orbital to the empty upper one, rather than from the lower to the upper Hubbard subbands; (2) a Mott transition generically of first order even at zero temperature. We simulate by means of time-dependent Gutzwiller approximation the evolution within the insulating phase of an initial state endowed by a nonequilibrium population of electrons in the upper orbital and holes in the lower one. We find that the excess population may lead, above a threshold, to a gap collapse and drive the insulator into the metastable metallic phase within the coexistence region around the Mott transition. This result foresees a nonthermal pathway to revert a Mott insulator into a metal. Even though this physical scenario is uncovered in a very specific toy model, we argue it might apply to other Mott insulating materials that share similar features.

  13. Mixed Bose-Fermi Mott Phases and Phase Transitions

    NASA Astrophysics Data System (ADS)

    Altman, Ehud

    2012-02-01

    A recent experiment with an ultra-cold mixture of ^174Yb and ^173Yb atoms in an optical lattice [S. Sugawa e. al. Nature Physics 7, 642 (2011)] found a remarkable quantum phase that can be described as a mixed Mott insulator. Such a an incompressible state established at integer combined filling of the two species, must have residual low energy Fermionic degrees of freedom associated with relative motion of the two species. I will discuss the novel quantum states formed by the composite Fermions in the mixed Mott insulator as well as the unconventional phase transitions separating these states from the compressible Bose-Fermi mixture established at weak interactions. Finally I will propose to utilize the mixed Mott insulator as a quantum simulator for models of the doped Mott insulator relevant to high Tc superconductivity. The new approach, where the bosonic atoms play the role of doped holes offers significant advantages over direct simulation of the Hubbard model. In particular the mixed Mott plateau naturally provides a flat trap potential to the doped holes, while the hole doping is easily tuned by varying the relative fraction of the bosons.

  14. Site-resolved imaging of a fermionic Mott insulator

    NASA Astrophysics Data System (ADS)

    Chiu, Christie; Greif, Daniel; Parsons, Maxwell F.; Mazurenko, Anton; Blatt, Sebastian; Huber, Florian; Ji, Geoffrey; Greiner, Markus

    2016-05-01

    Quantum gas microscopy of ultracold fermionic atoms in an optical lattice opens new perspectives for addressing long-standing open questions on strongly correlated low-temperature phases in the Hubbard model. Here we report on site-resolved imaging of two-component fermionic Mott insulators, metals, and band insulators with Lithium-6. For strong repulsive interactions we observe Mott insulators with more than 400 atoms and for intermediate interactions we observe a coexistence of phases. From comparison to theory, we find trap-averaged entropies per particle of 1 . 0kB in the Mott insulator and local entropies in the band insulator as low as 0 . 5kB . Our measurements serve as a benchmark for the performance of our experiment and are a starting point for accessing the low-temperature regime of magnetic ordering. Current address: Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany.

  15. Excitonic correlation in the Mott crossover regime in Ge

    NASA Astrophysics Data System (ADS)

    Sekiguchi, Fumiya; Shimano, Ryo

    2015-04-01

    Exciton Mott transition (EMT) in Ge was investigated by using optical-pump and terahertz-probe spectroscopy. From the quantitative analysis of optical conductivity and dielectric function, we evaluated the densities of unbound electron-hole pairs and excitons after the photoexcitation, from which we determined the ionization ratio of excitons α. The Mott crossover density region in Ge was elucidated from the density dependence of α in the temperature range above the critical temperature of electron-hole droplets. The 1 s -2 p excitonic transition energy hardly shifted with increasing density toward the EMT. Combined with the similar results recently observed in bulk Si, we suggest that the robustness of excitonic correlation against the Coulomb screening is a universal feature in bulk semiconductors in the Mott crossover regime.

  16. Electronic Griffiths Phases and Quantum Criticality at Disordered Mott Transitions

    NASA Astrophysics Data System (ADS)

    Dobrosavljevic, Vladimir

    2012-02-01

    The effects of disorder are investigated in strongly correlated electronic systems near the Mott metal-insulator transition. Correlation effects are foundootnotetextE. C. Andrade, E. Miranda, and V. Dobrosavljevic, Phys. Rev. Lett., 102, 206403 (2009). to lead to strong disorder screening, a mechanism restricted to low-lying electronic states, very similar to what is observed in underdoped cuprates. These results suggest, however, that this effect is not specific to disordered d-wave superconductors, but is a generic feature of all disordered Mott systems. In addition, the resulting spatial inhomogeneity rapidly increasesootnotetextE. C. Andrade, E. Miranda, and V. Dobrosavljevic, Phys. Rev. Lett., 104 (23), 236401 (2010). as the Mott insulator is approached at fixed disorder strength. This behavior, which can be described as an Electronic Griffiths Phase, displays all the features expected for disorder-dominated Infinite-Randomness Fixed Point scenario of quantum criticality.

  17. Breakdown of Strong Coupling Expansions for doped Mott Insulators

    NASA Astrophysics Data System (ADS)

    Phillips, Philip; Galanakis, Dimitrios; Stanescu, Tudor

    2005-03-01

    We show that doped Mott insulators, such as the copper-oxide superconductors, are asymptotically slaved in that the quasiparticle weight, Z, near half-filling depends critically on the existence of the high energy scale set by the upper Hubbard band. In particular, near half filling, the following dichotomy arises: Z0 when the high energy scale is integrated out but Z=0 in the thermodynamic limit when it is retained. Slavery to the high energy scale arises from quantum interference between electronic excitations across the Mott gap.

  18. Drude and Superconducting Weights and Mott Transitions in Variation Theory

    NASA Astrophysics Data System (ADS)

    Tamura, Shun; Yokoyama, Hisatoshi

    2015-06-01

    The Drude weight (D) is a useful measure for distinguishing a metal from an insulator. However, D has not been justifiably estimated using variation theory for a long time, since Millis and Coppersmith [Phys. Rev. B 43, 13770 (1991)] pointed out that the variational wave function ΨQ, which includes the key ingredient (doublon-holon binding effect) for a Mott transition, yields a positive D (namely, metallic) even in the Mott insulating regime. We argue that, to obtain a correct D, an imaginary part must exist in the wave function. By introducing a configuration-dependent phase factor Pθ to ΨQ, Mott transitions are successfully represented by D (D = 0 for U > Uc) for normal and d-wave pairing states; thus, the problem of Millis and Coppersmith is solved. Generally, Pθ plays a pivotal role in describing current-carrying states in the regime of Mott physics. On the other hand, we show using perturbation theory that the one-body (mean-field) part of the wave function should be complex for band insulators such as antiferromagnetic states in hypercubic lattices.

  19. Pressure-Induced Confined Metal from the Mott Insulator Sr_{3}Ir_{2}O_{7}.

    PubMed

    Ding, Yang; Yang, Liuxiang; Chen, Cheng-Chien; Kim, Heung-Sik; Han, Myung Joon; Luo, Wei; Feng, Zhenxing; Upton, Mary; Casa, Diego; Kim, Jungho; Gog, Thomas; Zeng, Zhidan; Cao, Gang; Mao, Ho-Kwang; van Veenendaal, Michel

    2016-05-27

    The spin-orbit Mott insulator Sr_{3}Ir_{2}O_{7} provides a fascinating playground to explore insulator-metal transition driven by intertwined charge, spin, and lattice degrees of freedom. Here, we report high-pressure electric resistance and resonant inelastic x-ray scattering measurements on single-crystal Sr_{3}Ir_{2}O_{7} up to 63-65 GPa at 300 K. The material becomes a confined metal at 59.5 GPa, showing metallicity in the ab plane but an insulating behavior along the c axis. Such an unusual phenomenon resembles the strange metal phase in cuprate superconductors. Since there is no sign of the collapse of spin-orbit or Coulomb interactions in x-ray measurements, this novel insulator-metal transition is potentially driven by a first-order structural change at nearby pressures. Our discovery points to a new approach for synthesizing functional materials. PMID:27284666

  20. Chiral magnetism and spin liquid Mott insulators induced by synthetic gauge fields

    NASA Astrophysics Data System (ADS)

    Paramekanti, Arun; Hickey, Ciaran; Cincio, Lukasz; Papic, Zlatko; Vellat-Sadashivan, Arun; Sohal, Ramanjit

    2016-05-01

    Recent experiments using Raman-assisted tunneling or lattice-shaking have realized synthetic gauge fields and optical lattice bands with nontrivial band topology. Here we examine the effect of particle interactions in such bands, focussing on two-component fermions with local Hubbard repulsion. We show that interactions can drive the integer quantum Hall insulator into Mott insulating states which possess noncoplanar chiral magnetic textures and even chiral spin liquids with many-body topological order. We establish our results using a combination of mean field theory, strong coupling expansions, numerical exact diagonalization and DMRG methods. We also discuss possible signatures of such non-coplanar orders in Bragg scattering and noise measurements.

  1. Pressure-Induced Confined Metal from the Mott Insulator Sr3 Ir2 O7

    NASA Astrophysics Data System (ADS)

    Ding, Yang; Yang, Liuxiang; Chen, Cheng-Chien; Kim, Heung-Sik; Han, Myung Joon; Luo, Wei; Feng, Zhenxing; Upton, Mary; Casa, Diego; Kim, Jungho; Gog, Thomas; Zeng, Zhidan; Cao, Gang; Mao, Ho-kwang; van Veenendaal, Michel

    2016-05-01

    The spin-orbit Mott insulator Sr3Ir2O7 provides a fascinating playground to explore insulator-metal transition driven by intertwined charge, spin, and lattice degrees of freedom. Here, we report high-pressure electric resistance and resonant inelastic x-ray scattering measurements on single-crystal Sr3Ir2O7 up to 63-65 GPa at 300 K. The material becomes a confined metal at 59.5 GPa, showing metallicity in the a b plane but an insulating behavior along the c axis. Such an unusual phenomenon resembles the strange metal phase in cuprate superconductors. Since there is no sign of the collapse of spin-orbit or Coulomb interactions in x-ray measurements, this novel insulator-metal transition is potentially driven by a first-order structural change at nearby pressures. Our discovery points to a new approach for synthesizing functional materials.

  2. Mott insulators and the doping-induced Mott transition within DMFT: exact results for the one-band Hubbard model

    NASA Astrophysics Data System (ADS)

    Logan, David E.; Galpin, Martin R.

    2016-01-01

    The paramagnetic phase of the one-band Hubbard model is studied at zero-temperature, within the framework of dynamical mean-field theory, and for general particle-hole asymmetry where a doping-induced Mott transition occurs. Our primary focus is the Mott insulator (MI) phase, and our main aim to establish what can be shown exactly about it. To handle the locally doubly-degenerate MI requires two distinct self-energies, which reflect the broken symmetry nature of the phase and together determine the standard single self-energy. Exact results are obtained for the local charge, local magnetic moment and associated spin susceptibilities, the interaction-renormalised levels, and the low-energy behaviour of the self-energy in the MI phase. The metallic phase is also considered briefly, and shown to acquire an emergent particle-hole symmetry as the Mott transition is approached. Throughout the metal, Luttinger’s theorem is reflected in the vanishing of the Luttinger integral; for the generic MI by contrast this is shown to be non-vanishing, but again to have a universal magnitude. Numerical results are also obtained using NRG, for the metal/MI phase boundary, the scaling behaviour of the charge as the Mott transition is aproached from the metal, and associated universal scaling of single-particle dynamics as the low-energy Kondo scale vanishes.

  3. Orbital magnetism induced by heat currents in Mott insulators.

    PubMed

    Lin, Shi-Zeng; Batista, Cristian D

    2013-10-18

    We derive the effective heat current density operator for the strong-coupling regime of Mott insulators. Similarly to the case of the electric current density, the leading contribution to this effective operator is proportional to the local scalar spin chirality χ(jkl)=S(l)·(S(j)×S(k)). This common form of the effective heat and electric current density operators leads to a novel cross response in Mott insulators. A heat current induces a distribution of orbital magnetic moments in systems containing loops of an odd number of hopping terms. The relative orientation of the orbital moments depends on the particular lattice of magnetic ions. This subtle effect arises from the symmetries that the heat and electric currents have in common. PMID:24182288

  4. Theory of high Tc ferrimagnetism in a multiorbital Mott insulator.

    PubMed

    Meetei, O Nganba; Erten, Onur; Randeria, Mohit; Trivedi, Nandini; Woodward, Patrick

    2013-02-22

    We propose a model for the multiorbital material Sr(2)CrOsO(6), an insulator with remarkable magnetic properties and the highest T(c) ~/= 725 K among all perovskites with a net moment. We derive a new criterion for the Mott transition (U(1)U(2))(1/2)>2.5W by using slave-rotor mean field theory, where W is the bandwidth and U(1(2)) are the effective Coulomb interactions on Cr(Os) including Hund's coupling. We show that Sr(2)CrOsO(6) is a Mott insulator, where the large Cr U(1) compensates for the small Os U(2). The spin sector is described by a frustrated antiferromagnetic Heisenberg model that naturally explains the net moment arising from canting and also the observed nonmonotonic magnetization M(T). We predict characteristic magnetic structure factor peaks that can be probed by neutron experiments.

  5. Theoretical prediction of fragile Mott insulators on plaquette Hubbard lattices

    NASA Astrophysics Data System (ADS)

    Wu, Han-Qing; He, Rong-Qiang; Meng, Zi Yang; Lu, Zhong-Yi

    2015-03-01

    Employing extensive cellular dynamical mean-field theory calculations with an exact diagonalization impurity solver, we investigate the ground-state phase diagrams and nonmagnetic metal-insulator transitions of the half-filled Hubbard model on two plaquette (the 1/5 depleted and checkerboard) square lattices. We identify three different insulators in the phase diagrams: dimer insulator, antiferromagnetic insulator, and plaquette insulator. We also demonstrate that the plaquette insulator is a novel fragile Mott insulator (FMI) which features a nontrivial one-dimensional irreducible representation of the C4 v crystalline point group and cannot be adiabatically connected to any band insulator with time-reversal symmetry. Furthermore, we study the nonmagnetic quantum phase transitions from the metal to the FMI and find that this Mott metal-insulator transition is characterized by the splitting of the noninteracting bands due to interaction effects.

  6. Compressibility of a fermionic mott insulator of ultracold atoms.

    PubMed

    Duarte, Pedro M; Hart, Russell A; Yang, Tsung-Lin; Liu, Xinxing; Paiva, Thereza; Khatami, Ehsan; Scalettar, Richard T; Trivedi, Nandini; Hulet, Randall G

    2015-02-20

    We characterize the Mott insulating regime of a repulsively interacting Fermi gas of ultracold atoms in a three-dimensional optical lattice. We use in situ imaging to extract the central density of the gas and to determine its local compressibility. For intermediate to strong interactions, we observe the emergence of a plateau in the density as a function of atom number, and a reduction of the compressibility at a density of one atom per site, indicating the formation of a Mott insulator. Comparisons to state-of-the-art numerical simulations of the Hubbard model over a wide range of interactions reveal that the temperature of the gas is of the order of, or below, the tunneling energy scale. Our results hold great promise for the exploration of many-body phenomena with ultracold atoms, where the local compressibility can be a useful tool to detect signatures of different phases or phase boundaries at specific values of the filling. PMID:25763942

  7. Mott metal-insulator transition on compressible lattices.

    PubMed

    Zacharias, Mario; Bartosch, Lorenz; Garst, Markus

    2012-10-26

    The critical properties of the finite temperature Mott end point are drastically altered by a coupling to crystal elasticity, i.e., whenever it is amenable to pressure tuning. Similar as for critical piezoelectric ferroelectrics, the Ising criticality of the electronic system is preempted by an isostructural instability, and long-range shear forces suppress microscopic fluctuations. As a result, the end point is governed by Landau criticality. Its hallmark is, thus, a breakdown of Hooke's law of elasticity with a nonlinear strain-stress relation characterized by a mean-field exponent. Based on a quantitative estimate, we predict critical elasticity to dominate the temperature range ΔT*/T(c)≃8%, close to the Mott end point of κ-(BEDT-TTF)(2)X. PMID:23215206

  8. Mott Criticality and Pseudogap in Bose-Fermi Mixtures

    NASA Astrophysics Data System (ADS)

    Altman, Ehud; Demler, Eugene; Rosch, Achim

    2012-12-01

    We study the Mott transition of a mixed Bose-Fermi system of ultracold atoms in an optical lattice, where the number of (spinless) fermions and bosons adds up to one atom per lattice, nF+nB=1. For weak interactions, a Fermi surface coexists with a Bose-Einstein condensate while for strong interaction the system is incompressible but still characterized by a Fermi surface of composite fermions. At the critical point, the spectral function of the fermions A(k,ω) exhibits a pseudogapped behavior, rising as |ω| at the Fermi momentum, while in the Mott phase it is fully gapped. Taking into account the interaction between the critical modes leads at very low temperatures either to p-wave pairing or the transition is driven weakly first order. The same mechanism should also be important in antiferromagnetic metals with a small Fermi surface.

  9. Site-resolved imaging of a fermionic Mott insulator.

    PubMed

    Greif, Daniel; Parsons, Maxwell F; Mazurenko, Anton; Chiu, Christie S; Blatt, Sebastian; Huber, Florian; Ji, Geoffrey; Greiner, Markus

    2016-02-26

    The complexity of quantum many-body systems originates from the interplay of strong interactions, quantum statistics, and the large number of quantum-mechanical degrees of freedom. Probing these systems on a microscopic level with single-site resolution offers important insights. Here we report site-resolved imaging of two-component fermionic Mott insulators, metals, and band insulators, using ultracold atoms in a square lattice. For strong repulsive interactions, we observed two-dimensional Mott insulators containing over 400 atoms. For intermediate interactions, we observed a coexistence of phases. From comparison to theory, we find trap-averaged entropies per particle of 1.0 times the Boltzmann constant (k(B)). In the band insulator, we find local entropies as low as 0.5 k(B). Access to local observables will aid the understanding of fermionic many-body systems in regimes inaccessible by modern theoretical methods.

  10. Constitutive relations associated with the Mott-Smith distribution function

    USGS Publications Warehouse

    Nathenson, M.; Baganoff, D.

    1973-01-01

    It is shown that the distribution function assumed by Mott-Smith determines a unique relation between heat flux, stress, and fluid velocity given by q = (3/2)??u, i.e., it provides a constitutive relation for heat flux, and it also determines a simple expression for this ratio of third-order central moments Q = . These expressions allow the equation of transfer for c x2 to be cast in a form that yields a nonlinear constitutive relation for stress. The results obtained from the Mott-Smith ansatz are compared with the theory of Baganoff and Nathenson and results from a numerical solution of the Boltzmann equation for shock-wave structure obtained by Hicks and Yen.

  11. How fast can a Peierls-Mott insulator be melted?

    PubMed

    Sohrt, C; Stange, A; Bauer, M; Rossnagel, K

    2014-01-01

    Time- and angle-resolved extreme ultraviolet photoemission spectroscopy is used to directly determine the momentum-dependent electronic structure dynamics in the layered Peierls-Mott insulators 1T-TaS(2) and 1T-TaSe(2) on the sub-300 fs time scale. Extracted spectroscopic order parameters display a global two-time-scale dynamics indicating a quasi-instantaneous loss of the electronic orders and a subsequent coherent suppression of the lattice distortion on a time scale related to the frequency of the charge-density-wave amplitude mode. After one half-cycle of coherent amplitude-mode vibration, a crossover state between insulator and metal with partially filled-in and partially closed Mott and Peierls gaps is reached. The results are discussed within the wider context of electronic order quenching in complex materials. PMID:25415852

  12. Optical properties of a vibrationally modulated solid state Mott insulator.

    PubMed

    Kaiser, S; Clark, S R; Nicoletti, D; Cotugno, G; Tobey, R I; Dean, N; Lupi, S; Okamoto, H; Hasegawa, T; Jaksch, D; Cavalleri, A

    2014-01-01

    Optical pulses at THz and mid-infrared frequencies tuned to specific vibrational resonances modulate the lattice along chosen normal mode coordinates. In this way, solids can be switched between competing electronic phases and new states are created. Here, we use vibrational modulation to make electronic interactions (Hubbard-U) in Mott-insulator time dependent. Mid-infrared optical pulses excite localized molecular vibrations in ET-F2TCNQ, a prototypical one-dimensional Mott-insulator. A broadband ultrafast probe interrogates the resulting optical spectrum between THz and visible frequencies. A red-shifted charge-transfer resonance is observed, consistent with a time-averaged reduction of the electronic correlation strength U. Secondly, a sideband manifold inside of the Mott-gap appears, resulting from a periodically modulated U. The response is compared to computations based on a quantum-modulated dynamic Hubbard model. Heuristic fitting suggests asymmetric holon-doublon coupling to the molecules and that electron double-occupancies strongly squeeze the vibrational mode.

  13. Charge relaxation and recombination in photo-excited Mott insulators

    NASA Astrophysics Data System (ADS)

    Prelovšek, P.; Lenarčič, Z.

    2016-04-01

    Recent femtosecond pump-probe experiments on Mott insulators reveal charge recombination, which is in picosecond range, i.e., much faster than in clean bandgap semiconductors although excitation gaps in Mott insulators are even larger. The charge response in photo-excited insulators can be generally divided in femtosecond transient relaxation of charge excitations, which are holons and doublons, and a second slower, but still very fast, holon-doublon (HD) recombination. We present a theory of the recombination rate of the excited HD pairs, based on the two-dimensional (2D) model relevant for cuprates, which shows that such fast processes can be explained even quantitatively with the multi-magnon emission. We show that the condition for the exponential decay as observed in the experiment is the existence of the exciton, i.e., the bound HD pair. Its recombination rate is exponentially dependent on the charge gap and on the magnon energy, while the ultrafast process can be traced back to strong charge-spin coupling. We comment also fast recombination times in the one-dimensional (1D) Mott insulators, as e.g., organic salts. The recombination rate in the latter cases can be explained with the stronger coupling with phonon excitations.

  14. Doping induced Mott transition in the two dimensional Hubbard model

    NASA Astrophysics Data System (ADS)

    Sordi, Giovanni; Tremblay, A.-M. S.

    2010-03-01

    The description of the Mott transition by single-site dynamical mean-field theory is exact in infinite dimensions but, in two dimensions, substantial deviations from those results have been found for the interaction driven transition [1]. In addition, the experimentally relevant transition for layered systems such as the high-Tc cuprates is doping driven. We thus study this transition in the two dimensional Hubbard model on the square lattice using cluster dynamical mean-field theory with continuous-time quantum Monte Carlo in the hybridization expansion [2]. We find that the Mott transition is strongly influenced by the inclusion of short-range antiferromagnetic correlations. Doping of the Mott insulating state occurs gradually in the different momentum sectors, as found in previous studies [3], but in addition we find a first order transition between an incoherent metal and an insulator or between two incoherent metals, depending on interaction strength. Short range spin correlations create a pseudogap in a doping range that increases with interaction. [1] H. Park et al., PRL 101, 186403 (2008) [2] K. Haule, PRB 75, 155113 (2007) [3] E. Gull et al., arXiv:0909.1795 (2009)

  15. Phase fluctuation in overdoped cuprates? Superconducting dome due to Mott-ness of the tightly bound preformed pairs

    NASA Astrophysics Data System (ADS)

    Ku, Wei; Yang, Fan

    2015-03-01

    In contrast to the current lore, we demonstrate that even the overdoped cuprates suffer from superconducting phase fluctuation in the strong binding limit. Specifically, the Mott-ness of the underlying doped holes dictates naturally a generic optimal doping around 15% and nearly complete loss of phase coherence around 25%, giving rise to a dome shape of superconducting transition temperature in excellent agreement with experimental observations of the cuprates. We verify this effect with a simple estimation using Gutzwiller approximation of the preformed pairs, obtained through variational Monte Carlo calculation. This realization suggests strongly the interesting possibility that the high-temperature superconductivity in the cuprates might be mostly described by Bose-Einstein condensation, without crossing over to amplitude fluctuating Cooper pairs. Supported by Department of Energy, Office of Basic Energy Science DE-AC02-98CH10886.

  16. Doping-driven evolution of the superconducting state from a doped Mott insulator: Cluster dynamical mean-field theory

    NASA Astrophysics Data System (ADS)

    Civelli, M.

    2009-05-01

    In this paper we investigate the zero-temperature doping-driven evolution of a superconductor toward the Mott insulator in a two-dimensional electron model, relevant for high-temperature superconductivity. To this purpose we use a cluster extension of dynamical mean-field theory. Our results show that a standard d -wave superconductor, realized at high doping, is driven into the Mott insulator via an intermediate superconducting state displaying unconventional physical properties. By restoring the translational invariance of the lattice, we give an interpretation of these findings in momentum space. In particular, we show that at a finite doping a strong momentum-space differentiation takes place: non-Fermi liquid and insulatinglike (pseudogap) characters rise in some regions (antinodes), while Fermi liquid quasiparticles survive in other regions (nodes) of momentum space. We describe the consequence of these happenings on the spectral properties, stressing in particular the behavior of the superconducting gap, which reveals two distinct nodal and antinodal energy scales as a function of doping, detected in photoemission and Raman spectroscopy experiments. We study and compare with experimental results the doping-dependent behavior of other physical quantities, such as for instance, the nodal quasiparticle velocity (extracted in angle-resolved photoemission) and the low-energy slopes of the local density of states and of the Raman scattering response. We then propose a description of the evolution of the electronic structure while approaching the Mott transition. We show that, within our formalism, a strong asymmetry naturally arises in the local density of states, measured in scanning tunneling spectroscopy. We investigate in detail the doping evolution of the electronic bands, focusing on the kinklike quasiparticle dispersion observed with angle-resolved photoemission in specific cuts of the momentum-energy space. We finally show the consequences of the

  17. Superfluid - Mott transition in the presence of artificial gauge fields

    NASA Astrophysics Data System (ADS)

    Vasic, Ivana; Petrescu, Alex; Le Hur, Karyn; Hofstetter, Walter

    2014-05-01

    Several recent cold atom experiments reported implementation of artificial gauge fields in optical lattice systems, paving the way toward observation of new phases of matter. Here we study the tight-binding model on the honeycomb lattice introduced by Haldane, for lattice bosons. We analyze the ground state topology and quasiparticle properties in the Mott phase by applying bosonic dynamical mean field theory, strong-coupling perturbation theory and exact diagonalization. The phase diagram also contains two different superfluid phases. The quasiparticle dynamics, number fluctuations, and local currents are measurable in cold atom experiments.

  18. Fractional quantum Hall states in the vicinity of Mott plateaus

    SciTech Connect

    Umucalilar, R. O.; Mueller, Erich J.

    2010-05-15

    We perform variational Monte Carlo calculations to show that bosons in a rotating optical lattice will form analogs of fractional quantum Hall states when the tunneling is sufficiently weak compared to the interactions, and the deviation of density from an integer is commensurate with the effective magnetic field. We compare the energies of superfluid and correlated states to one another and to the energies found in full configuration-interaction calculations on small systems. We look at overlaps between our variational states and the exact ground state, characterizing the ways in which fractional quantum Hall effect correlations manifest themselves near the Mott insulating state. We explore the experimental signatures of these states.

  19. Orbital Ordering and Frustration of p-Band Mott Insulators

    SciTech Connect

    Wu Congjun

    2008-05-23

    We investigate the general structure of orbital exchange physics in Mott-insulating states of p-orbital systems in optical lattices. Orbital orders occur in both the triangular and kagome lattices. In contrast, orbital exchange in the honeycomb lattice is frustrated as described by a novel quantum 120 deg. model. Its classical ground states are mapped into configurations of the fully packed loop model with an extra U(1) rotation degree of freedom. Quantum orbital fluctuations select a six-site plaquette ground state ordering pattern in the semiclassical limit from the 'order from disorder' mechanism. This effect arises from the appearance of a zero energy flat band of orbital excitations.

  20. Charge dynamics of the antiferromagnetically ordered Mott insulator

    NASA Astrophysics Data System (ADS)

    Han, Xing-Jie; Liu, Yu; Liu, Zhi-Yuan; Li, Xin; Chen, Jing; Liao, Hai-Jun; Xie, Zhi-Yuan; Normand, B.; Xiang, Tao

    2016-10-01

    We introduce a slave-fermion formulation in which to study the charge dynamics of the half-filled Hubbard model on the square lattice. In this description, the charge degrees of freedom are represented by fermionic holons and doublons and the Mott-insulating characteristics of the ground state are the consequence of holon–doublon bound-state formation. The bosonic spin degrees of freedom are described by the antiferromagnetic Heisenberg model, yielding long-ranged (Néel) magnetic order at zero temperature. Within this framework and in the self-consistent Born approximation, we perform systematic calculations of the average double occupancy, the electronic density of states, the spectral function and the optical conductivity. Qualitatively, our method reproduces the lower and upper Hubbard bands, the spectral-weight transfer into a coherent quasiparticle band at their lower edges and the renormalisation of the Mott gap, which is associated with holon–doublon binding, due to the interactions of both quasiparticle species with the magnons. The zeros of the Green function at the chemical potential give the Luttinger volume, the poles of the self-energy reflect the underlying quasiparticle dispersion with a spin-renormalised hopping parameter and the optical gap is directly related to the Mott gap. Quantitatively, the square-lattice Hubbard model is one of the best-characterised problems in correlated condensed matter and many numerical calculations, all with different strengths and weaknesses, exist with which to benchmark our approach. From the semi-quantitative accuracy of our results for all but the weakest interaction strengths, we conclude that a self-consistent treatment of the spin-fluctuation effects on the charge degrees of freedom captures all the essential physics of the antiferromagnetic Mott–Hubbard insulator. We remark in addition that an analytical approximation with these properties serves a vital function in developing a full understanding of

  1. Proximity effects in a topological-insulator/Mott-insulator heterostructure

    NASA Astrophysics Data System (ADS)

    Ueda, Suguru; Kawakami, Norio; Sigrist, Manfred

    2013-04-01

    We investigate proximity effects in a correlated heterostructure of a two-dimensional Mott insulator (MI) and a topological insulator (TI) by employing inhomogeneous dynamical mean-field theory. We show that the edge state of the TI induces strongly renormalized midgap states inside the MI region, which still have a remnant of the helical energy spectrum. The penetration of low-energy electrons, which is controlled by the interface tunneling V, largely enhances the electron mass inside the MI and also splits a single Dirac cone at edge sites into the spatially separated two Dirac cones in the strong V region.

  2. Cabrera-Mott kinetics of oxidation of metal nanowires

    NASA Astrophysics Data System (ADS)

    Zhdanov, Vladimir P.; Kasemo, Bengt

    2012-06-01

    The Cabrera-Mott model, implying that oxidation of a metal is limited by the field-facilitated activated jumps of metal ions at the metal-oxide interface, was originally proposed to interpret growth of thin oxide films on planar metal surfaces. Recently, the model was used to describe oxidation of spherical nanoparticles with small radius of curvature. Here, we analyze oxidation of nanowires. The increase of the oxide thickness with increasing time for a nanowire is shown to be slower than that for a nanoparticle with the same radius, but faster than in the case of a planar surface.

  3. Lucretia Mott: Friend of Justice. With a Message from Rosalynn Carter. Picture-book Biography Series.

    ERIC Educational Resources Information Center

    Sawyer, Kem Knapp

    An illustrated biography for children features Lucretia Mott, one of the pioneers of the movement for womens' rights. Born in 1793, Lucretia Mott was raised a Quaker; her strong spiritual beliefs underlay her outspoken advocacy of equal rights for women and blacks, and against war. Lucretia became a leader among those who wished to abolish…

  4. Spectral properties near the Mott transition in the two-dimensional Hubbard model

    NASA Astrophysics Data System (ADS)

    Kohno, Masanori

    2013-03-01

    Single-particle excitations near the Mott transition in the two-dimensional (2D) Hubbard model are investigated by using cluster perturbation theory. The Mott transition is characterized by the loss of the spectral weight from the dispersing mode that leads continuously to the spin-wave excitation of the Mott insulator. The origins of the dominant modes of the 2D Hubbard model near the Mott transition can be traced back to those of the one-dimensional Hubbard model. Various anomalous spectral features observed in cuprate high-temperature superconductors, such as the pseudogap, Fermi arc, flat band, doping-induced states, hole pockets, and spinon-like and holon-like branches, as well as giant kink and waterfall in the dispersion relation, are explained in a unified manner as properties near the Mott transition in a 2D system.

  5. Mott physics and spin fluctuations: A functional viewpoint

    NASA Astrophysics Data System (ADS)

    Ayral, Thomas; Parcollet, Olivier

    2016-06-01

    We present a formalism for strongly correlated systems with fermions coupled to bosonic modes. We construct the three-particle irreducible functional K by successive Legendre transformations of the free energy of the system. We derive a closed set of equations for the fermionic and bosonic self-energies for a given K . We then introduce a local approximation for K , which extends the idea of dynamical mean-field theory (DMFT) approaches from two- to three-particle irreducibility. This approximation entails the locality of the three-leg electron-boson vertex Λ (i ω ,i Ω ) , which is self-consistently computed using a quantum impurity model with dynamical charge and spin interactions. This local vertex is used to construct frequency- and momentum-dependent electronic self-energies and polarizations. By construction, the method interpolates between the spin-fluctuation or G W approximations at weak coupling and the atomic limit at strong coupling. We apply it to the Hubbard model on two-dimensional square and triangular lattices. We complement the results of [T. Ayral and O. Parcollet, Phys. Rev. B 92, 115109 (2015), 10.1103/PhysRevB.92.115109] by (i) showing that, at half-filling, as DMFT, the method describes the Fermi-liquid metallic state and the Mott insulator, separated by a first-order interaction-driven Mott transition at low temperatures, (ii) investigating the influence of frustration, and (iii) discussing the influence of the bosonic decoupling channel.

  6. Novel Pauli-paramagnetic quantum phase in a Mott insulator.

    PubMed

    Watanabe, D; Yamashita, M; Tonegawa, S; Oshima, Y; Yamamoto, H M; Kato, R; Sheikin, I; Behnia, K; Terashima, T; Uji, S; Shibauchi, T; Matsuda, Y

    2012-01-01

    In Mott insulators, the strong electron-electron Coulomb repulsion localizes electrons. In dimensions greater than one, their spins are usually ordered antiferromagnetically at low temperatures. Geometrical frustrations can destroy this long-range order, leading to exotic quantum spin liquid states. However, their magnetic ground states have been a long-standing mystery. Here we show that a quantum spin liquid state in the organic Mott insulator EtMe(3)Sb[Pd(dmit)(2)](2) (where Et is C(2)H(5)-, Me is CH(3)-, and dmit is 1,3-dithiole-2-thione-4,5-dithiolate) with two-dimensional triangular lattice has Pauli-paramagnetic-like low-energy excitations, which are a hallmark of itinerant fermions. Our torque magnetometry down to low temperatures (30 mK) up to high fields (32 T) reveals distinct residual paramagnetic susceptibility comparable to that in a half-filled two-dimensional metal, demonstrating the magnetically gapless nature of the ground state. Moreover, our results are robust against deuteration, pointing toward the emergence of an extended 'quantum critical phase', in which low-energy spin excitations behave as in paramagnetic metals with Fermi surface, despite the frozen charge degree of freedom.

  7. The Mott-Hubbard Insulator: localization and topological quantum order

    NASA Astrophysics Data System (ADS)

    Martin, Richard M.

    2010-03-01

    An insulating state of condensed matter is characterized by localization of the center of mass of the electrons. This criterion can be addressed in terms of the ground state on a torus with boundary conditions ψK(x1+L,x2, ) = exp( i K L) ψK(x1,x2, ). As shown by Kohn[1], in an insulator the energy is insensitive to K as L ->∞, whereas in an ideal metal it increases as K^2. In addition, Souza, et al. derived expressions for the localization length in terms of the wavefunction as a function of K. The present work generalizes the arguments to provide a fundamental distinction between ``band'' and ``Mott-Hubbard'' insulators. The criteria involve only counting of electrons and experimentally measurable quantities independent of models, and they lead to the requirement that a Mott-Hubbard insulator with no broken local symmetry must have topological quantum order.[4pt] [1] W. Kohn, Phys. Rev. 133, A171 (1964)[0pt] [2] I. Souza, et al., Phys. Rev. B 62, 1666 (2000).

  8. Mott-Ioffe-Regel limit and resistivity crossover in a tractable electron-phonon model

    NASA Astrophysics Data System (ADS)

    Werman, Yochai; Berg, Erez

    2016-02-01

    Many metals display resistivity saturation—a substantial decrease in the slope of the resistivity as a function of temperature that occurs when the electron scattering rate τ-1 becomes comparable to the Fermi energy EF/ℏ (the Mott-Ioffe-Regel limit). At such temperatures, the usual description of a metal in terms of ballistically propagating quasiparticles is no longer valid. We present a tractable model of a large number N of electronic bands coupled to N2 optical phonon modes, which displays a crossover behavior in the resistivity at temperatures where τ-1˜EF/ℏ . At low temperatures, the resistivity obeys the familiar linear form, while at high temperatures, the resistivity still increases linearly, but with a modified slope (that can be either lower or higher than the low-temperature slope, depending on the band structure). The high-temperature non-Boltzmann regime is interpreted by considering the diffusion constant and the compressibility, both of which scale as the inverse square root of the temperature.

  9. Mott-insulator phases of spin-3/2 fermions in the presence of quadratic Zeeman coupling.

    PubMed

    Rodríguez, K; Argüelles, A; Colomé-Tatché, M; Vekua, T; Santos, L

    2010-07-30

    We study the influence of the quadratic Zeeman effect on the Mott-insulator phases of hard-core 1D spin-3/2 fermions. We show that, contrary to spinor bosons, the quadratic Zeeman coupling preserves an SU(2)⊗SU(2) symmetry, leading for large-enough quadratic Zeeman coupling to an isotropic pseudo-spin-1/2 Heisenberg antiferromagnet. Decreasing the quadratic Zeeman coupling, this phase undergoes, depending on the scattering lengths, either a Kosterlitz-Thouless transition into a gapped dimerized phase or a commensurate-incommensurate transition into a gapless spin liquid. This rich phase diagram can be observed experimentally in four-component fermions in optical lattices under similar entropy constraints to those needed for Néel order in spin-1/2 gases.

  10. Mott-insulator phases of spin-3/2 fermions in the presence of quadratic Zeeman coupling

    SciTech Connect

    Rodriguez, K.; Argueelles, A.; Colome-Tatche, M.; Vekua, T.; Santos, L.

    2010-07-30

    We study the influence of the quadratic Zeeman effect on the Mott-insulator phases of hard-core 1D spin-3/2 fermions. We show that, contrary to spinor bosons, the quadratic Zeeman coupling preserves an SU(2) x SU(2) symmetry, leading for large-enough quadratic Zeeman coupling to an isotropic pseudo-spin-1/2 Heisenberg antiferromagnet. Decreasing the quadratic Zeeman coupling, this phase undergoes, depending on the scattering lengths, either a Kosterlitz-Thouless transition into a gapped dimerized phase or a commensurate-incommensurate transition into a gapless spin liquid. This rich phase diagram can be observed experimentally in four-component fermions in optical lattices under similar entropy constraints to those needed for Neel order in spin-1/2 gases.

  11. Cluster Mott insulators and two Curie-Weiss regimes on an anisotropic kagome lattice

    NASA Astrophysics Data System (ADS)

    Chen, Gang; Kee, Hae-Young; Kim, Yong Baek

    2016-06-01

    Motivated by recent experiments on the quantum-spin-liquid candidate material LiZn2Mo3O8 , we study a single-band extended Hubbard model on an anisotropic kagome lattice with the 1/6 electron filling. Due to the partial filling of the lattice, the intersite repulsive interaction is necessary to generate Mott insulators, where electrons are localized in clusters rather than at lattice sites. It is shown that these cluster Mott insulators are generally U(1) quantum spin liquids with spinon Fermi surfaces. The nature of charge excitations in cluster Mott insulators can be quite different from conventional Mott insulator and we show that there exists a cluster Mott insulator where charge fluctuations around the hexagonal cluster induce a plaquette charge order (PCO). The spinon excitation spectrum in this spin-liquid cluster Mott insulator is reconstructed due to the PCO so that only 1/3 of the total spinon excitations are magnetically active. Based on these results, we propose that the two Curie-Weiss regimes of the spin susceptibility in LiZn2Mo3O8 may be explained by finite-temperature properties of the cluster Mott insulator with the PCO as well as fractionalized spinon excitations. Existing and possible future experiments on LiZn2Mo3O8 , and other Mo-based cluster magnets are discussed in light of these theoretical predictions.

  12. Wannier-Mott excitons in semiconductors with a superlattice

    SciTech Connect

    Suris, R. A.

    2015-06-15

    The effect of the motion of a Wannier-Mott exciton in semiconductors with a superlattice formed by heterojunctions on the exciton binding energy and wave function is analyzed. This effect arises as a result of the fact that the dispersion laws of the electron and hole that form an exciton in a superlattice differ from the quadratic law. The investigated one-dimensional superlattice consists of alternating semiconductor layers with different energy positions of the conduction and valence bands, i.e., with one-dimensional wells and barriers. The exciton state in a superlattice consisting of quantum dots is analyzed. It is demonstrated that the closer the electron and hole effective masses, the greater the dependence of the binding energy on the exciton quasi-momentum. The possibility of replacing the tunneling excitation transfer between superlattice cells with the dipole-dipole one at certain exciton quasi-wave vector values is investigated.

  13. Slowdown of the Electronic Relaxation Close to the Mott Transition.

    PubMed

    Sayyad, Sharareh; Eckstein, Martin

    2016-08-26

    We investigate the time-dependent reformation of the quasiparticle peak in a correlated metal near the Mott transition, after the system is quenched into a hot electron state and equilibrates with an environment which is colder than the Fermi-liquid crossover temperature. Close to the transition, we identify a purely electronic bottleneck time scale, which depends on the spectral weight around the Fermi energy in the bad metallic phase in a nonlinear way. This time scale can be orders of magnitude larger than the bare and renormalized electronic hopping time, so that a separation of electronic and lattice time scales may break down. The results are obtained using nonequilibrium dynamical mean-field theory and a slave-rotor representation of the Anderson impurity model. PMID:27610867

  14. Critical conductance of a one-dimensional doped Mott insulator

    NASA Astrophysics Data System (ADS)

    Garst, M.; Novikov, D. S.; Stern, Ady; Glazman, L. I.

    2008-01-01

    We consider the two-terminal conductance of a one-dimensional Mott insulator undergoing the commensurate-incommensurate quantum phase transition to a conducting state. We treat the leads as Luttinger liquids. At a specific value of compressibility of the leads, corresponding to the Luther-Emery point, the conductance can be described in terms of the free propagation of noninteracting fermions with charge e/2 . At that point, the temperature dependence of the conductance across the quantum phase transition is described by a Fermi function. The deviation from the Luther-Emery point in the leads changes the temperature dependence qualitatively. In the metallic state, the low-temperature conductance is determined by the properties of the leads, and is described by the conventional Luttinger-liquid theory. In the insulating state, conductance occurs via activation of e/2 charges, and is independent of the Luttinger-liquid compressibility.

  15. Ge doping of GaN beyond the Mott transition

    NASA Astrophysics Data System (ADS)

    Ajay, A.; Schörmann, J.; Jiménez-Rodriguez, M.; Lim, C. B.; Walther, F.; Rohnke, M.; Mouton, I.; Amichi, L.; Bougerol, C.; Den Hertog, M. I.; Eickhoff, M.; Monroy, E.

    2016-11-01

    We present a study of germanium as n-type dopant in wurtzite GaN films grown by plasma-assisted molecular-beam epitaxy, reaching carrier concentrations of up to 6.7  ×  1020 cm‑3 at 300 K, well beyond the Mott density. The Ge concentration and free carrier density were found to scale linearly with the Ge flux in the studied range. All the GaN:Ge layers present smooth surface morphology with atomic terraces, without trace of pits or cracks, and the mosaicity of the samples has no noticeable dependence on the Ge concentration. The variation of the GaN:Ge band gap with the carrier concentration is consistent with theoretical calculations of the band gap renormalization due to electron–electron and electron–ion interaction, and Burstein–Moss effect.

  16. Slowdown of the Electronic Relaxation Close to the Mott Transition

    NASA Astrophysics Data System (ADS)

    Sayyad, Sharareh; Eckstein, Martin

    2016-08-01

    We investigate the time-dependent reformation of the quasiparticle peak in a correlated metal near the Mott transition, after the system is quenched into a hot electron state and equilibrates with an environment which is colder than the Fermi-liquid crossover temperature. Close to the transition, we identify a purely electronic bottleneck time scale, which depends on the spectral weight around the Fermi energy in the bad metallic phase in a nonlinear way. This time scale can be orders of magnitude larger than the bare and renormalized electronic hopping time, so that a separation of electronic and lattice time scales may break down. The results are obtained using nonequilibrium dynamical mean-field theory and a slave-rotor representation of the Anderson impurity model.

  17. First-order superfluid to Mott-insulator phase transitions in spinor condensates

    NASA Astrophysics Data System (ADS)

    Chen, Zihe; Jiang, Jie; Zhao, Lichao; Wang, Shengtao; Tang, Tao; Duan, Luming; Liu, Yingmei

    2016-05-01

    We observe evidence of first-order superfluid to Mott-insulator quantum phase transitions in a lattice-confined antiferromagnetic spinor Bose-Einstein condensate. The observed signatures include hysteresis effect, significant heatings across the phase transitions, and evolutions of spin populations due to the formation of spin singlets in the Mott-insulator phase. The nature of the phase transitions is found to strongly depend on the ratio of the quadratic Zeeman energy to the spin-dependent interaction. Our observations are qualitatively understood by the mean field theory, and in addition suggest tuning the quadratic Zeeman energy is a new approach to realize superfluid to Mott-insulator phase transitions.

  18. First-order superfluid-to-Mott-insulator phase transitions in spinor condensates

    NASA Astrophysics Data System (ADS)

    Jiang, J.; Zhao, L.; Wang, S.-T.; Chen, Z.; Tang, T.; Duan, L.-M.; Liu, Y.

    2016-06-01

    We observe evidence of first-order superfluid-to-Mott-insulator quantum phase transitions in a lattice-confined antiferromagnetic spinor Bose-Einstein condensate. The observed signatures include the hysteresis effect, significant heatings across the phase transitions, and changes in spin populations due to the formation of spin singlets in the Mott-insulator phase. The nature of the phase transitions is found to strongly depend on the ratio of the quadratic Zeeman energy to the spin-dependent interaction. Our observations are qualitatively understood by the mean field theory and suggest tuning the quadratic Zeeman energy is a new approach to realize superfluid-to-Mott-insulator phase transitions.

  19. A cylindrically symmetric "micro-Mott" electron polarimeter.

    PubMed

    Clayburn, N B; Brunkow, E; Burtwistle, S J; Rutherford, G H; Gay, T J

    2016-05-01

    A small, novel, cylindrically symmetric Mott electron polarimeter is described. The effective Sherman function, Seff, or analyzing power, for 20 kV Au target bias with a 1.3 keV energy loss window is 0.16 ± 0.01, where uncertainty in the measurement is due primarily to uncertainty in the incident electron polarization. For an energy loss window of 0.5 keV, Seff reaches its maximum value of 0.24 ± 0.02. The device's maximum efficiency, I/Io, defined as the detected count rate divided by the incident particle rate, is 3.7 ± 0.2 × 10(-4) at 20 keV. The figure-of-merit of the device, η, is defined as Seff (2)IIo and equals 9.0 ± 1.6 × 10(-6). Potential sources of false asymmetries due to detector electronic asymmetry and beam misalignment have been investigated. The new polarimeter's performance is compared to published results for similar compact retarding-field Mott polarimeters, and it is concluded that this device has a relatively large Seff and low efficiency. SIMION(®) electron trajectory simulations and Sherman function calculations are presented to explain the differences in performance between this device and previous designs. This design has an Seff that is insensitive to spatial beam fluctuations and, for an energy loss window >0.5 keV, negligible background due to spurious ion and X-ray production at the target. PMID:27250409

  20. A cylindrically symmetric "micro-Mott" electron polarimeter

    NASA Astrophysics Data System (ADS)

    Clayburn, N. B.; Brunkow, E.; Burtwistle, S. J.; Rutherford, G. H.; Gay, T. J.

    2016-05-01

    A small, novel, cylindrically symmetric Mott electron polarimeter is described. The effective Sherman function, Seff, or analyzing power, for 20 kV Au target bias with a 1.3 keV energy loss window is 0.16 ± 0.01, where uncertainty in the measurement is due primarily to uncertainty in the incident electron polarization. For an energy loss window of 0.5 keV, Seff reaches its maximum value of 0.24 ± 0.02. The device's maximum efficiency, I/Io, defined as the detected count rate divided by the incident particle rate, is 3.7 ± 0.2 × 10-4 at 20 keV. The figure-of-merit of the device, η, is defined as Seff2I/Io and equals 9.0 ± 1.6 × 10-6. Potential sources of false asymmetries due to detector electronic asymmetry and beam misalignment have been investigated. The new polarimeter's performance is compared to published results for similar compact retarding-field Mott polarimeters, and it is concluded that this device has a relatively large Seff and low efficiency. SIMION® electron trajectory simulations and Sherman function calculations are presented to explain the differences in performance between this device and previous designs. This design has an Seff that is insensitive to spatial beam fluctuations and, for an energy loss window >0.5 keV, negligible background due to spurious ion and X-ray production at the target.

  1. Spin Hall Effects Due to Phonon Skew Scattering

    NASA Astrophysics Data System (ADS)

    Gorini, Cosimo; Eckern, Ulrich; Raimondi, Roberto

    2015-08-01

    A diversity of spin Hall effects in metallic systems is known to rely on Mott skew scattering. In this work its high-temperature counterpart, phonon skew scattering, which is expected to be of foremost experimental relevance, is investigated. In particular, the phonon skew scattering spin Hall conductivity is found to be practically T independent for temperatures above the Debye temperature TD. As a consequence, in Rashba-like systems a high-T linear behavior of the spin Hall angle demonstrates the dominance of extrinsic spin-orbit scattering only if the intrinsic spin splitting is smaller than the temperature.

  2. Bragg scattering as a probe of atomic wave functions and quantum phase transitions in optical lattices.

    PubMed

    Miyake, Hirokazu; Siviloglou, Georgios A; Puentes, Graciana; Pritchard, David E; Ketterle, Wolfgang; Weld, David M

    2011-10-21

    We have observed Bragg scattering of photons from quantum degenerate ^{87}Rb atoms in a three-dimensional optical lattice. Bragg scattered light directly probes the microscopic crystal structure and atomic wave function whose position and momentum width is Heisenberg limited. The spatial coherence of the wave function leads to revivals in the Bragg scattered light due to the atomic Talbot effect. The decay of revivals across the superfluid to Mott insulator transition indicates the loss of superfluid coherence.

  3. Bragg scattering as a probe of atomic wave functions and quantum phase transitions in optical lattices.

    PubMed

    Miyake, Hirokazu; Siviloglou, Georgios A; Puentes, Graciana; Pritchard, David E; Ketterle, Wolfgang; Weld, David M

    2011-10-21

    We have observed Bragg scattering of photons from quantum degenerate ^{87}Rb atoms in a three-dimensional optical lattice. Bragg scattered light directly probes the microscopic crystal structure and atomic wave function whose position and momentum width is Heisenberg limited. The spatial coherence of the wave function leads to revivals in the Bragg scattered light due to the atomic Talbot effect. The decay of revivals across the superfluid to Mott insulator transition indicates the loss of superfluid coherence. PMID:22107532

  4. Unusual Mott transition in multiferroic PbCrO 3

    SciTech Connect

    Wang, Shanmin; Zhu, Jinlong; Zhang, Yi; Yu, Xiaohui; Zhang, Jianzhong; Wang, Wendan; Bai, Ligang; Qian, Jiang; Yin, Liang; Sullivan, Neil S.; Jin, Changqing; He, Duanwei; Xu, Jian; Zhao, Yusheng

    2015-11-24

    The Mott insulator in correlated electron systems arises from classical Coulomb repulsion between carriers to provide a powerful force for electron localization. When turning such an insulator into a metal, the so-called Mott transition, is commonly achieved by "bandwidth" control or "band filling." However, both mechanisms deviate from the original concept of Mott, which attributes such a transition to the screening of Coulomb potential and associated lattice contraction. We report a pressure-induced isostructural Mott transition in cubic perovskite PbCrO3. At the transition pressure of similar to 3 GPa, PbCrO3 exhibits significant collapse in both lattice volume and Coulomb potential. Concurrent with the collapse, it transforms from a hybrid multiferroic insulator to a metal. For the first time to our knowledge, these findings validate the scenario conceived by Mott. Close to the Mott criticality at similar to 300 K, fluctuations of the lattice and charge give rise to elastic anomalies and Laudau critical behaviors resembling the classic liquid-gas transition. Moreover, the anomalously large lattice volume and Coulomb potential in the low-pressure insulating phase are largely associated with the ferroelectric distortion, which is substantially suppressed at high pressures, leading to the first-order phase transition without symmetry breaking.

  5. Anderson localization and Mott insulator phase in the time domain.

    PubMed

    Sacha, Krzysztof

    2015-01-01

    Particles in space periodic potentials constitute standard models for investigation of crystalline phenomena in solid state physics. Time periodicity of periodically driven systems is a close analogue of space periodicity of solid state crystals. There is an intriguing question if solid state phenomena can be observed in the time domain. Here we show that wave-packets localized on resonant classical trajectories of periodically driven systems are ideal elements to realize Anderson localization or Mott insulator phase in the time domain. Uniform superpositions of the wave-packets form stationary states of a periodically driven particle. However, an additional perturbation that fluctuates in time results in disorder in time and Anderson localization effects emerge. Switching to many-particle systems we observe that depending on how strong particle interactions are, stationary states can be Bose-Einstein condensates or single Fock states where definite numbers of particles occupy the periodically evolving wave-packets. Our study shows that non-trivial crystal-like phenomena can be observed in the time domain. PMID:26074169

  6. Anderson localization and Mott insulator phase in the time domain

    PubMed Central

    Sacha, Krzysztof

    2015-01-01

    Particles in space periodic potentials constitute standard models for investigation of crystalline phenomena in solid state physics. Time periodicity of periodically driven systems is a close analogue of space periodicity of solid state crystals. There is an intriguing question if solid state phenomena can be observed in the time domain. Here we show that wave-packets localized on resonant classical trajectories of periodically driven systems are ideal elements to realize Anderson localization or Mott insulator phase in the time domain. Uniform superpositions of the wave-packets form stationary states of a periodically driven particle. However, an additional perturbation that fluctuates in time results in disorder in time and Anderson localization effects emerge. Switching to many-particle systems we observe that depending on how strong particle interactions are, stationary states can be Bose-Einstein condensates or single Fock states where definite numbers of particles occupy the periodically evolving wave-packets. Our study shows that non-trivial crystal-like phenomena can be observed in the time domain. PMID:26074169

  7. Designing Quantum Spin-Orbital Liquids in Artificial Mott Insulators.

    PubMed

    Dou, Xu; Kotov, Valeri N; Uchoa, Bruno

    2016-08-24

    Quantum spin-orbital liquids are elusive strongly correlated states of matter that emerge from quantum frustration between spin and orbital degrees of freedom. A promising route towards the observation of those states is the creation of artificial Mott insulators where antiferromagnetic correlations between spins and orbitals can be designed. We show that Coulomb impurity lattices on the surface of gapped honeycomb substrates, such as graphene on SiC, can be used to simulate SU(4) symmetric spin-orbital lattice models. We exploit the property that massive Dirac fermions form mid-gap bound states with spin and valley degeneracies in the vicinity of a Coulomb impurity. Due to electronic repulsion, the antiferromagnetic correlations of the impurity lattice are driven by a super-exchange interaction with SU(4) symmetry, which emerges from the bound states degeneracy at quarter filling. We propose that quantum spin-orbital liquids can be engineered in artificially designed solid-state systems at vastly higher temperatures than achievable in optical lattices with cold atoms. We discuss the experimental setup and possible scenarios for candidate quantum spin-liquids in Coulomb impurity lattices of various geometries.

  8. Nature of strong hole pairing in doped Mott antiferromagnets.

    PubMed

    Zhu, Zheng; Jiang, Hong-Chen; Sheng, D N; Weng, Zheng-Yu

    2014-06-24

    Cooper pairing instability in a Fermi liquid is well understood by the BCS theory, but pairing mechanism for doped Mott insulators still remains elusive. Previously it has been shown by density matrix renormalization group (DMRG) method that a single doped hole is always self-localized due to the quantum destructive interference of the phase string signs hidden in the t-J ladders. Here we report a DMRG investigation of hole binding in the same model, where a novel pairing-glue scheme beyond the BCS realm is discovered. Specifically, we show that, in addition to spin pairing due to superexchange interaction, the strong frustration of the phase string signs on the kinetic energy gets effectively removed by pairing the charges, which results in strong binding of two holes. By contrast, if the phase string signs are "switched off" artificially, the pairing strength diminishes significantly even if the superexchange coupling remains the same. In the latter, unpaired holes behave like coherent quasiparticles with pairing drastically weakened, whose sole origin may be attributed to the resonating-valence-bond (RVB) pairing of spins. Such non-BCS pairing mechanism is therefore beyond the RVB picture and may shed important light on the high-T(c) cuprate superconductors.

  9. Designing Quantum Spin-Orbital Liquids in Artificial Mott Insulators.

    PubMed

    Dou, Xu; Kotov, Valeri N; Uchoa, Bruno

    2016-01-01

    Quantum spin-orbital liquids are elusive strongly correlated states of matter that emerge from quantum frustration between spin and orbital degrees of freedom. A promising route towards the observation of those states is the creation of artificial Mott insulators where antiferromagnetic correlations between spins and orbitals can be designed. We show that Coulomb impurity lattices on the surface of gapped honeycomb substrates, such as graphene on SiC, can be used to simulate SU(4) symmetric spin-orbital lattice models. We exploit the property that massive Dirac fermions form mid-gap bound states with spin and valley degeneracies in the vicinity of a Coulomb impurity. Due to electronic repulsion, the antiferromagnetic correlations of the impurity lattice are driven by a super-exchange interaction with SU(4) symmetry, which emerges from the bound states degeneracy at quarter filling. We propose that quantum spin-orbital liquids can be engineered in artificially designed solid-state systems at vastly higher temperatures than achievable in optical lattices with cold atoms. We discuss the experimental setup and possible scenarios for candidate quantum spin-liquids in Coulomb impurity lattices of various geometries. PMID:27553516

  10. Nature of strong hole pairing in doped Mott antiferromagnets

    NASA Astrophysics Data System (ADS)

    Zhu, Zheng; Jiang, Hong-Chen; Sheng, D. N.; Weng, Zheng-Yu

    2014-06-01

    Cooper pairing instability in a Fermi liquid is well understood by the BCS theory, but pairing mechanism for doped Mott insulators still remains elusive. Previously it has been shown by density matrix renormalization group (DMRG) method that a single doped hole is always self-localized due to the quantum destructive interference of the phase string signs hidden in the t-J ladders. Here we report a DMRG investigation of hole binding in the same model, where a novel pairing-glue scheme beyond the BCS realm is discovered. Specifically, we show that, in addition to spin pairing due to superexchange interaction, the strong frustration of the phase string signs on the kinetic energy gets effectively removed by pairing the charges, which results in strong binding of two holes. By contrast, if the phase string signs are ``switched off'' artificially, the pairing strength diminishes significantly even if the superexchange coupling remains the same. In the latter, unpaired holes behave like coherent quasiparticles with pairing drastically weakened, whose sole origin may be attributed to the resonating-valence-bond (RVB) pairing of spins. Such non-BCS pairing mechanism is therefore beyond the RVB picture and may shed important light on the high-Tc cuprate superconductors.

  11. Towards a photonic Mott insulator in superconducting circuits

    NASA Astrophysics Data System (ADS)

    Ma, Ruichao; Owen, John C.; Schuster, David; Simon, Jonathan

    2016-05-01

    Recent developments in circuit QED provide superconducting circuits as a unique platform for exploring quantum many-body phenomena with light. The absence of particle number conservation, however, makes creating and understanding of many-body photonic states challenging. Here we make a one-dimensional lattice of coupled superconducting qubits with an additional pumping site and a lossy site incorporated at the end of the chain, which serves as an effective chemical potential for photons. When driven on the pumping site, the photons can spontaneously thermalize into the ground state of the lattice while the excess energy is dissipated via the lossy site. In the presence of strong photon-photon interaction via the qubit non-linearity, we expect the creation of a Mott insulator state of light, which we probe with temporal- and spatially-resolved measurements. These experiments will give insights to the microscopic investigation of non-equilibrium thermodynamics in strongly-interacting quantum system, including the interplay between external driving and dissipation.

  12. Nature of strong hole pairing in doped Mott antiferromagnets.

    PubMed

    Zhu, Zheng; Jiang, Hong-Chen; Sheng, D N; Weng, Zheng-Yu

    2014-01-01

    Cooper pairing instability in a Fermi liquid is well understood by the BCS theory, but pairing mechanism for doped Mott insulators still remains elusive. Previously it has been shown by density matrix renormalization group (DMRG) method that a single doped hole is always self-localized due to the quantum destructive interference of the phase string signs hidden in the t-J ladders. Here we report a DMRG investigation of hole binding in the same model, where a novel pairing-glue scheme beyond the BCS realm is discovered. Specifically, we show that, in addition to spin pairing due to superexchange interaction, the strong frustration of the phase string signs on the kinetic energy gets effectively removed by pairing the charges, which results in strong binding of two holes. By contrast, if the phase string signs are "switched off" artificially, the pairing strength diminishes significantly even if the superexchange coupling remains the same. In the latter, unpaired holes behave like coherent quasiparticles with pairing drastically weakened, whose sole origin may be attributed to the resonating-valence-bond (RVB) pairing of spins. Such non-BCS pairing mechanism is therefore beyond the RVB picture and may shed important light on the high-T(c) cuprate superconductors. PMID:24957467

  13. Designing Quantum Spin-Orbital Liquids in Artificial Mott Insulators

    DOE PAGESBeta

    Dou, Xu; Kotov, Valeri N.; Uchoa, Bruno

    2016-08-24

    Quantum spin-orbital liquids are elusive strongly correlated states of matter that emerge from quantum frustration between spin and orbital degrees of freedom. A promising route towards the observation of those states is the creation of artificial Mott insulators where antiferromagnetic correlations between spins and orbitals can be designed. We show that Coulomb impurity lattices on the surface of gapped honeycomb substrates, such as graphene on SiC, can be used to simulate SU(4) symmetric spin-orbital lattice models. We exploit the property that massive Dirac fermions form mid-gap bound states with spin and valley degeneracies in the vicinity of a Coulomb impurity.more » Due to electronic repulsion, the antiferromagnetic correlations of the impurity lattice are driven by a super-exchange interaction with SU(4) symmetry, which emerges from the bound states degeneracy at quarter filling. We propose that quantum spin-orbital liquids can be engineered in artificially designed solid-state systems at vastly higher temperatures than achievable in optical lattices with cold atoms. Lastly, we discuss the experimental setup and possible scenarios for candidate quantum spin-liquids in Coulomb impurity lattices of various geometries.« less

  14. Möbius molecules and fragile Mott insulators

    NASA Astrophysics Data System (ADS)

    Muechler, Lukas; Maciejko, Joseph; Neupert, Titus; Car, Roberto

    2014-12-01

    Motivated by the concept of Möbius aromatics in organic chemistry, we extend the recently introduced concept of fragile Mott insulators (FMI) to ring-shaped molecules with repulsive Hubbard interactions threaded by a half-quantum of magnetic flux (h c /2 e ) . In this context, an FMI is the insulating ground state of a finite-size molecule that cannot be adiabatically connected to a single Slater determinant, i.e., to a band insulator, provided that time-reversal and lattice translation symmetries are preserved. Based on exact numerical diagonalization for finite Hubbard interaction strength U and existing Bethe-ansatz studies of the one-dimensional Hubbard model in the large-U limit, we establish a duality between Hubbard molecules with 4 n and 4 n +2 sites, with n integer. A molecule with 4 n sites is an FMI in the absence of flux but becomes a band insulator in the presence of a half-quantum of flux, while a molecule with 4 n +2 sites is a band insulator in the absence of flux but becomes an FMI in the presence of a half-quantum of flux. Including next-nearest-neighbor hoppings gives rise to new FMI states that belong to multidimensional irreducible representations of the molecular point group, giving rise to a rich phase diagram.

  15. Möbius molecules and fragile Mott insulators

    NASA Astrophysics Data System (ADS)

    Muechler, Lukas; Maciejko, Joseph; Neupert, Titus; Car, Roberto

    2015-03-01

    Motivated by the concept of Möbius aromatics in organic chemistry, we extend the recently introduced concept of fragile Mott insulators (FMI) to ring-shaped molecules with repulsive Hubbard interactions threaded by a half-quantum of magnetic flux (hc / 2 e). In this context, a FMI is the insulating ground state of a finite-size molecule that cannot be adiabatically connected to a single Slater determinant, i.e., to a band insulator, provided that time-reversal and lattice translation symmetries are preserved. Based on exact numerical diagonalization for finite Hubbard interaction strength U and existing Bethe-ansatz studies of the one-dimensional Hubbard model in the large- U limit, we establish a duality between Hubbard molecules with 4 n and 4 n + 2 sites, with n integer. A molecule with 4 n sites is an FMI in the absence of flux but becomes a band insulator in the presence of a half-quantum of flux, while a molecule with 4 n + 2 sites is a band insulator in the absence of flux but becomes an FMI in the presence of a half-quantum of flux. Including next-nearest-neighbor-hoppings gives rise to new FMI states that belong to multidimensional irreducible representations of the molecular point group, giving rise to a rich phase diagram. Reference: arXiv:1409.6732

  16. Chiral Bosonic Mott Insulator on the Frustrated Triangular Lattice

    NASA Astrophysics Data System (ADS)

    Parameswaran, Siddharth; Zaletel, Michael; Rüegg, Andreas; Altman, Ehud

    2014-03-01

    We study the superfluid and insulating phases of interacting bosons on the triangular lattice with an inverted dispersion, corresponding to frustrated hopping between sites. The resulting single-particle dispersion has multiple minima at nonzero wavevectors in momentum space, in contrast to the unique zero-wavevector minimum of the unfrustrated problem. As a consequence, the superfluid phase is unstable against developing additional chiral order that breaks time reversal (T) and parity (P) symmetries by forming a condensate at nonzero wavevector. We demonstrate that the loss of superfluidity can lead to an even more exotic phase, the chiral Mott insulator, with nontrivial current order that breaks T, P. These results are obtained via variational estimates, as well as a combination of bosonization and DMRG of triangular ladders, which taken together permit a fairly complete characterization of the phase diagram. We discuss the relevance of these phases to optical lattice experiments, as well as signatures of chiral symmetry breaking in time-of-flight images. We acknowledge support from NSF Grants 1066293 (SP, EA) and DGE-1106400 (MPZ), the Simons Foundation (SP), the Swiss National Science Foundation (AR), the ISF, BSF, ERC Synergy UQUAM program and the Miller Institute at UC Berkeley (EA).

  17. Chiral bosonic Mott insulator on the frustrated triangular lattice

    NASA Astrophysics Data System (ADS)

    Zaletel, Michael P.; Parameswaran, S. A.; Rüegg, Andreas; Altman, Ehud

    2014-04-01

    We study the superfluid and insulating phases of interacting bosons on the triangular lattice with an inverted dispersion, corresponding to frustrated hopping between sites. The resulting single-particle dispersion has multiple minima at nonzero wave vectors in momentum space, in contrast to the unique zero-wave-vector minimum of the unfrustrated problem. As a consequence, the superfluid phase is unstable against developing additional chiral order that breaks time-reversal (T) and parity (P) symmetries by forming a condensate at nonzero wave vector. We demonstrate that the loss of superfluidity can lead to an even more exotic phase, the chiral Mott insulator, with nontrivial current order that breaks T ,P. These results are obtained via variational estimates, as well as a combination of bosonization and density-matrix renormalization group of triangular ladders, which, taken together, permit a fairly complete characterization of the phase diagram. We discuss the relevance of these phases to optical lattice experiments, as well as signatures of chiral symmetry breaking in time-of-flight images.

  18. Designing Quantum Spin-Orbital Liquids in Artificial Mott Insulators

    NASA Astrophysics Data System (ADS)

    Dou, Xu; Kotov, Valeri N.; Uchoa, Bruno

    2016-08-01

    Quantum spin-orbital liquids are elusive strongly correlated states of matter that emerge from quantum frustration between spin and orbital degrees of freedom. A promising route towards the observation of those states is the creation of artificial Mott insulators where antiferromagnetic correlations between spins and orbitals can be designed. We show that Coulomb impurity lattices on the surface of gapped honeycomb substrates, such as graphene on SiC, can be used to simulate SU(4) symmetric spin-orbital lattice models. We exploit the property that massive Dirac fermions form mid-gap bound states with spin and valley degeneracies in the vicinity of a Coulomb impurity. Due to electronic repulsion, the antiferromagnetic correlations of the impurity lattice are driven by a super-exchange interaction with SU(4) symmetry, which emerges from the bound states degeneracy at quarter filling. We propose that quantum spin-orbital liquids can be engineered in artificially designed solid-state systems at vastly higher temperatures than achievable in optical lattices with cold atoms. We discuss the experimental setup and possible scenarios for candidate quantum spin-liquids in Coulomb impurity lattices of various geometries.

  19. The amplitude mode at the superfluid-mott insulator transition

    NASA Astrophysics Data System (ADS)

    Pekker, David

    2012-02-01

    We study a two dimensional gas of repulsively interacting bosons in the presence of both an optical lattice and a trap using optical lattice modulation spectroscopy. The strongly interacting superfluid supports two types of low energy modes associated with the symmetry breaking at the phase transition: gapless phase (Goldstone) modes and gapped amplitude (Anderson-Higgs) modes. Both experimentally and in theoretical simulations lattice modulation spectroscopy shows an onset of absorption at a frequency associated with the amplitude mode gap, followed by a broad absorption peak at higher frequencies. From the simulations, we learn that energy is being absorbed by various amplitude modes, which inside a trap resemble the modes of a (gapped) drum. Our main results are: (1) despite coupling to the phase modes, modulation spectroscopy shows a sharp absorption onset at the frequency associated with the amplitude mode gap; (2) as we approach the Mott transition the gap softens and finally disappears at the transition point; (3) in the weak coupling regime, deep in the superfluid phase, the amplitude mode disappears.

  20. Designing Quantum Spin-Orbital Liquids in Artificial Mott Insulators

    PubMed Central

    Dou, Xu; Kotov, Valeri N.; Uchoa, Bruno

    2016-01-01

    Quantum spin-orbital liquids are elusive strongly correlated states of matter that emerge from quantum frustration between spin and orbital degrees of freedom. A promising route towards the observation of those states is the creation of artificial Mott insulators where antiferromagnetic correlations between spins and orbitals can be designed. We show that Coulomb impurity lattices on the surface of gapped honeycomb substrates, such as graphene on SiC, can be used to simulate SU(4) symmetric spin-orbital lattice models. We exploit the property that massive Dirac fermions form mid-gap bound states with spin and valley degeneracies in the vicinity of a Coulomb impurity. Due to electronic repulsion, the antiferromagnetic correlations of the impurity lattice are driven by a super-exchange interaction with SU(4) symmetry, which emerges from the bound states degeneracy at quarter filling. We propose that quantum spin-orbital liquids can be engineered in artificially designed solid-state systems at vastly higher temperatures than achievable in optical lattices with cold atoms. We discuss the experimental setup and possible scenarios for candidate quantum spin-liquids in Coulomb impurity lattices of various geometries. PMID:27553516

  1. Characteristics of a Mott field-effect transistor (MottFET) based on La1-xSrxMnO3

    NASA Astrophysics Data System (ADS)

    Lee, Suyoun; Lee, Keundong; Gwon, Hyojin; Baek, Seung-Hyub; Park, Baeho; Kim, Jin-Sang

    2013-03-01

    Recently, the metal-insulator transition (MIT) phenomenon shown in transition metal oxides has attracted much interest due to its superior characteristics such as fast switching speed (~ femtoseconds), high on/off ratio, and low power consumption. One example is the MottFET, which utilizes the MIT modulated by electric field through the band-filling in a Mott insulator. In this work, we examined MottFET devices based on La1-xSrxMnO3(LSMO), which is one of the mostly studied Mott insulators and attractive for the potential application in spintronic devices due to its intriguing properties such as colossal magnetoresistance (CMR) and half-metallicity. For the devices with the composition near the boundary of the metal-insulator transition, we confirmed that the conductivity of the channel could be modulated by a gate electric field of moderate strength. In addition, for the future application in spintronic devices, we investigated the dependence of device characteristics on the magnetic field. As the applied magnetic field increased, we found that the current-voltage characteristic showed anomalous behavior, which might be attributed to the electron-electron interaction, spin ordering, and the magnetic impurities in the channel. This work was supported by KIST Grant 2E22731 from Ministry of Educational Science and Technology.

  2. Characterizing Featureless Mott Insulating State by Quasiparticle Interferences - A DMFT Prospect

    NASA Astrophysics Data System (ADS)

    Mukherjee, Shantanu; Lee, Wei-Cheng

    In this talk we discuss the quasiparticle interferences (QPIs) of a Mott insulator using a T-matrix formalism implemented with the dynamical mean-field theory (T-DMFT). In the Mott insulating state, the DMFT predicts a singularity in the real part of electron self energy s (w) at low frequencies, which completely washes out the QPI at small bias voltage. However, the QPI patterns produced by the non-interacting Fermi surfaces can appear at a critical bias voltage in Mott insulating state. The existence of this non-zero critical bias voltage is a direct consequence of the singular behavior of Re[s (w)] /sim n/w with n behaving as the 'order parameter' of Mott insulating state. We propose that this reentry of non-interacting QPI patterns could serve as an experimental signature of Mott insulating state, and the 'order parameter' can be experimentally measured W.C.L acknowledges financial support from start up fund from Binghamton University.

  3. Effective field theory and integrability in two-dimensional Mott transition

    SciTech Connect

    Bottesi, Federico L.; Zemba, Guillermo R.

    2011-08-15

    Highlights: > Mott transition in 2d lattice fermion model. > 3D integrability out of 2D. > Effective field theory for Mott transition in 2d. > Double Chern-Simons. > d-Density waves. - Abstract: We study the Mott transition in a two-dimensional lattice spinless fermion model with nearest neighbors density-density interactions. By means of a two-dimensional Jordan-Wigner transformation, the model is mapped onto the lattice XXZ spin model, which is shown to possess a quantum group symmetry as a consequence of a recently found solution of the Zamolodchikov tetrahedron equation. A projection (from three to two space-time dimensions) property of the solution is used to identify the symmetry of the model at the Mott critical point as U{sub q}(sl(2)-circumflex)xU{sub q}(sl(2)-circumflex), with deformation parameter q = -1. Based on this result, the low-energy effective field theory for the model is obtained and shown to be a lattice double Chern-Simons theory with coupling constant k = 1 (with the standard normalization). By further employing the effective filed theory methods, we show that the Mott transition that arises is of topological nature, with vortices in an antiferromagnetic array and matter currents characterized by a d-density wave order parameter. We also analyze the behavior of the system upon weak coupling, and conclude that it undergoes a quantum gas-liquid transition which belongs to the Ising universality class.

  4. Electron-hole doping asymmetry of Fermi surface reconstructed in a simple Mott insulator.

    PubMed

    Kawasugi, Yoshitaka; Seki, Kazuhiro; Edagawa, Yusuke; Sato, Yoshiaki; Pu, Jiang; Takenobu, Taishi; Yunoki, Seiji; Yamamoto, Hiroshi M; Kato, Reizo

    2016-01-01

    It is widely recognized that the effect of doping into a Mott insulator is complicated and unpredictable, as can be seen by examining the Hall coefficient in high Tc cuprates. The doping effect, including the electron-hole doping asymmetry, may be more straightforward in doped organic Mott insulators owing to their simple electronic structures. Here we investigate the doping asymmetry of an organic Mott insulator by carrying out electric-double-layer transistor measurements and using cluster perturbation theory. The calculations predict that strongly anisotropic suppression of the spectral weight results in the Fermi arc state under hole doping, while a relatively uniform spectral weight results in the emergence of a non-interacting-like Fermi surface (FS) in the electron-doped state. In accordance with the calculations, the experimentally observed Hall coefficients and resistivity anisotropy correspond to the pocket formed by the Fermi arcs under hole doping and to the non-interacting FS under electron doping. PMID:27492864

  5. Quantum critical Mott transitions in a bilayer Kondo insulator-metal model system

    NASA Astrophysics Data System (ADS)

    Sen, Sudeshna; Vidhyadhiraja, N. S.

    2016-04-01

    A bilayer system comprising a Kondo insulator coupled to a simple metal (KI-M) is considered. Employing the framework of dynamical mean-field theory, the model system is shown to exhibit a surface of quantum critical points (QCPs) that separates a Kondo screened, Fermi liquid phase from a local moment, Mott insulating phase. The quantum critical nature of these Mott transitions is characterized by the vanishing of (a) the coherence scale on the Fermi liquid side, and (b) the Mott gap on the MI side. In contrast to the usual "large-to-small" Fermi surface (FS) QCPs in heavy-fermion systems, the bilayer KI-M system exhibits a complete FS destruction.

  6. Electron-hole doping asymmetry of Fermi surface reconstructed in a simple Mott insulator.

    PubMed

    Kawasugi, Yoshitaka; Seki, Kazuhiro; Edagawa, Yusuke; Sato, Yoshiaki; Pu, Jiang; Takenobu, Taishi; Yunoki, Seiji; Yamamoto, Hiroshi M; Kato, Reizo

    2016-01-01

    It is widely recognized that the effect of doping into a Mott insulator is complicated and unpredictable, as can be seen by examining the Hall coefficient in high Tc cuprates. The doping effect, including the electron-hole doping asymmetry, may be more straightforward in doped organic Mott insulators owing to their simple electronic structures. Here we investigate the doping asymmetry of an organic Mott insulator by carrying out electric-double-layer transistor measurements and using cluster perturbation theory. The calculations predict that strongly anisotropic suppression of the spectral weight results in the Fermi arc state under hole doping, while a relatively uniform spectral weight results in the emergence of a non-interacting-like Fermi surface (FS) in the electron-doped state. In accordance with the calculations, the experimentally observed Hall coefficients and resistivity anisotropy correspond to the pocket formed by the Fermi arcs under hole doping and to the non-interacting FS under electron doping.

  7. Electron-hole doping asymmetry of Fermi surface reconstructed in a simple Mott insulator

    NASA Astrophysics Data System (ADS)

    Kawasugi, Yoshitaka; Seki, Kazuhiro; Edagawa, Yusuke; Sato, Yoshiaki; Pu, Jiang; Takenobu, Taishi; Yunoki, Seiji; Yamamoto, Hiroshi M.; Kato, Reizo

    2016-08-01

    It is widely recognized that the effect of doping into a Mott insulator is complicated and unpredictable, as can be seen by examining the Hall coefficient in high Tc cuprates. The doping effect, including the electron-hole doping asymmetry, may be more straightforward in doped organic Mott insulators owing to their simple electronic structures. Here we investigate the doping asymmetry of an organic Mott insulator by carrying out electric-double-layer transistor measurements and using cluster perturbation theory. The calculations predict that strongly anisotropic suppression of the spectral weight results in the Fermi arc state under hole doping, while a relatively uniform spectral weight results in the emergence of a non-interacting-like Fermi surface (FS) in the electron-doped state. In accordance with the calculations, the experimentally observed Hall coefficients and resistivity anisotropy correspond to the pocket formed by the Fermi arcs under hole doping and to the non-interacting FS under electron doping.

  8. Tunnelling into the twisted Mott insulator Sr2IrO4 with atomic resolution

    NASA Astrophysics Data System (ADS)

    Ansary, Armin; Nichols, John; Bray-Ali, Noah; Cao, Gang; Ng, Kwok-Wai

    2014-03-01

    We studied the single-layered iridate Sr2IrO4 with a scanning tunneling microscope. The finite low temperature conductance enables the electronic structure of this antiferromagnetic Mott insulator to be measured by tunneling spectroscopy. We imaged the topography of freshly cleaved surfaces and measured differential tunneling conductance at cryogenic temperatures. We found the Mott gap in the tunneling density of states to be 2 Δ = 615 meV. Within the Mott gap, additional shoulders are observed which are interpreted as inelastic loss features due to magnons. This research was supported by NSF grants DMR- 0800367, DMR-0856234 and EPS-0814194. Noah Bray- Ali acknowledges support from the National Research Council Postdoctoral Research Associateship Program.

  9. Ultrafast energy- and momentum-resolved dynamics of magnetic correlations in the photo-doped Mott insulator Sr2IrO4.

    PubMed

    Dean, M P M; Cao, Y; Liu, X; Wall, S; Zhu, D; Mankowsky, R; Thampy, V; Chen, X M; Vale, J G; Casa, D; Kim, Jungho; Said, A H; Juhas, P; Alonso-Mori, R; Glownia, J M; Robert, A; Robinson, J; Sikorski, M; Song, S; Kozina, M; Lemke, H; Patthey, L; Owada, S; Katayama, T; Yabashi, M; Tanaka, Yoshikazu; Togashi, T; Liu, J; Rayan Serrao, C; Kim, B J; Huber, L; Chang, C-L; McMorrow, D F; Först, M; Hill, J P

    2016-06-01

    Measuring how the magnetic correlations evolve in doped Mott insulators has greatly improved our understanding of the pseudogap, non-Fermi liquids and high-temperature superconductivity. Recently, photo-excitation has been used to induce similarly exotic states transiently. However, the lack of available probes of magnetic correlations in the time domain hinders our understanding of these photo-induced states and how they could be controlled. Here, we implement magnetic resonant inelastic X-ray scattering at a free-electron laser to directly determine the magnetic dynamics after photo-doping the Mott insulator Sr2IrO4. We find that the non-equilibrium state, 2 ps after the excitation, exhibits strongly suppressed long-range magnetic order, but hosts photo-carriers that induce strong, non-thermal magnetic correlations. These two-dimensional (2D) in-plane Néel correlations recover within a few picoseconds, whereas the three-dimensional (3D) long-range magnetic order restores on a fluence-dependent timescale of a few hundred picoseconds. The marked difference in these two timescales implies that the dimensionality of magnetic correlations is vital for our understanding of ultrafast magnetic dynamics.

  10. Ultrafast energy- and momentum-resolved dynamics of magnetic correlations in the photo-doped Mott insulator Sr2IrO4.

    PubMed

    Dean, M P M; Cao, Y; Liu, X; Wall, S; Zhu, D; Mankowsky, R; Thampy, V; Chen, X M; Vale, J G; Casa, D; Kim, Jungho; Said, A H; Juhas, P; Alonso-Mori, R; Glownia, J M; Robert, A; Robinson, J; Sikorski, M; Song, S; Kozina, M; Lemke, H; Patthey, L; Owada, S; Katayama, T; Yabashi, M; Tanaka, Yoshikazu; Togashi, T; Liu, J; Rayan Serrao, C; Kim, B J; Huber, L; Chang, C-L; McMorrow, D F; Först, M; Hill, J P

    2016-06-01

    Measuring how the magnetic correlations evolve in doped Mott insulators has greatly improved our understanding of the pseudogap, non-Fermi liquids and high-temperature superconductivity. Recently, photo-excitation has been used to induce similarly exotic states transiently. However, the lack of available probes of magnetic correlations in the time domain hinders our understanding of these photo-induced states and how they could be controlled. Here, we implement magnetic resonant inelastic X-ray scattering at a free-electron laser to directly determine the magnetic dynamics after photo-doping the Mott insulator Sr2IrO4. We find that the non-equilibrium state, 2 ps after the excitation, exhibits strongly suppressed long-range magnetic order, but hosts photo-carriers that induce strong, non-thermal magnetic correlations. These two-dimensional (2D) in-plane Néel correlations recover within a few picoseconds, whereas the three-dimensional (3D) long-range magnetic order restores on a fluence-dependent timescale of a few hundred picoseconds. The marked difference in these two timescales implies that the dimensionality of magnetic correlations is vital for our understanding of ultrafast magnetic dynamics. PMID:27159018

  11. Ultrafast energy- and momentum-resolved dynamics of magnetic correlations in the photo-doped Mott insulator Sr2IrO4

    DOE PAGESBeta

    Dean, M. P. M.; Cao, Y.; Liu, X.; Wall, S.; Zhu, D.; Mankowsky, R.; Thampy, V.; Chen, X. M.; Vale, J. G.; Casa, D.; et al

    2016-05-09

    Measuring how the magnetic correlations evolve in doped Mott insulators has greatly improved our understanding of the pseudogap, non-Fermi liquids and high-temperature superconductivity1, 2, 3, 4. Recently, photo-excitation has been used to induce similarly exotic states transiently5, 6, 7. However, the lack of available probes of magnetic correlations in the time domain hinders our understanding of these photo-induced states and how they could be controlled. Here, we implement magnetic resonant inelastic X-ray scattering at a free-electron laser to directly determine the magnetic dynamics after photo-doping the Mott insulator Sr2IrO4. We find that the non-equilibrium state, 2 ps after the excitation,more » exhibits strongly suppressed long-range magnetic order, but hosts photo-carriers that induce strong, non-thermal magnetic correlations. These two-dimensional (2D) in-plane Néel correlations recover within a few picoseconds, whereas the three-dimensional (3D) long-range magnetic order restores on a fluence-dependent timescale of a few hundred picoseconds. In conclusion, the marked difference in these two timescales implies that the dimensionality of magnetic correlations is vital for our understanding of ultrafast magnetic dynamics.« less

  12. Ultrafast energy- and momentum-resolved dynamics of magnetic correlations in the photo-doped Mott insulator Sr2IrO4

    NASA Astrophysics Data System (ADS)

    Dean, M. P. M.; Cao, Y.; Liu, X.; Wall, S.; Zhu, D.; Mankowsky, R.; Thampy, V.; Chen, X. M.; Vale, J. G.; Casa, D.; Kim, Jungho; Said, A. H.; Juhas, P.; Alonso-Mori, R.; Glownia, J. M.; Robert, A.; Robinson, J.; Sikorski, M.; Song, S.; Kozina, M.; Lemke, H.; Patthey, L.; Owada, S.; Katayama, T.; Yabashi, M.; Tanaka, Yoshikazu; Togashi, T.; Liu, J.; Rayan Serrao, C.; Kim, B. J.; Huber, L.; Chang, C.-L.; McMorrow, D. F.; Först, M.; Hill, J. P.

    2016-06-01

    Measuring how the magnetic correlations evolve in doped Mott insulators has greatly improved our understanding of the pseudogap, non-Fermi liquids and high-temperature superconductivity. Recently, photo-excitation has been used to induce similarly exotic states transiently. However, the lack of available probes of magnetic correlations in the time domain hinders our understanding of these photo-induced states and how they could be controlled. Here, we implement magnetic resonant inelastic X-ray scattering at a free-electron laser to directly determine the magnetic dynamics after photo-doping the Mott insulator Sr2IrO4. We find that the non-equilibrium state, 2 ps after the excitation, exhibits strongly suppressed long-range magnetic order, but hosts photo-carriers that induce strong, non-thermal magnetic correlations. These two-dimensional (2D) in-plane Néel correlations recover within a few picoseconds, whereas the three-dimensional (3D) long-range magnetic order restores on a fluence-dependent timescale of a few hundred picoseconds. The marked difference in these two timescales implies that the dimensionality of magnetic correlations is vital for our understanding of ultrafast magnetic dynamics.

  13. New class of planar ferroelectric Mott insulators via first-principles design

    SciTech Connect

    Kim, Chanul; Park, Hyowon; Marianetti, Chris A.

    2015-12-11

    which is not common in known materials. Here we use first-principles calculations to design layered double perovskite oxides AABBO6 which achieve the aforementioned properties in the context of Mott insulators. In our design rules, the gap is dictated by B/B electronegativity difference in a Mott state, while the polarization is obtained via nominal d0 filling on the B-site, A-type cations bearing lone-pair electrons, and A = A size mismatch. Successful execution is demonstrated in BaBiCuVO6, BaBiNiVO6, BaLaCuVO6, and PbLaCuVO6.

  14. THz-Frequency Modulation of the Hubbard U in an Organic Mott Insulator.

    PubMed

    Singla, R; Cotugno, G; Kaiser, S; Först, M; Mitrano, M; Liu, H Y; Cartella, A; Manzoni, C; Okamoto, H; Hasegawa, T; Clark, S R; Jaksch, D; Cavalleri, A

    2015-10-30

    We use midinfrared pulses with stable carrier-envelope phase offset to drive molecular vibrations in the charge transfer salt ET-F_{2}TCNQ, a prototypical one-dimensional Mott insulator. We find that the Mott gap, which is probed resonantly with 10 fs laser pulses, oscillates with the pump field. This observation reveals that molecular excitations can coherently perturb the electronic on-site interactions (Hubbard U) by changing the local orbital wave function. The gap oscillates at twice the frequency of the vibrational mode, indicating that the molecular distortions couple quadratically to the local charge density.

  15. Mott Physics in lightly doped (Sr1-xLax)3Ir2O7

    NASA Astrophysics Data System (ADS)

    Affeldt, Gregory; Hogan, Tom; Smallwood, Christopher; Das, Tanmoy; Denlinger, Jonathan; Mo, Sung-Kwan; Wilson, Stephen; Lanzara, Alessandra

    The layered perovskite iridates Sr2IrO4 and Sr3Ir2O7 exhibit a spin-orbit Mott insulating state that becomes metallic upon sufficient carrier doping. While Sr2IrO4 presents striking similarities to cuprates upon electron doping, Sr3Ir2O7 appears to be a correlated metal. We show a detailed doping and temperature-dependent ARPES study which reveals important similarities between (Sr1-xLax)3Ir2O7 and doped Sr2IrO4, as well as other doped Mott insulators.

  16. Ultrahigh-resolution spin-resolved photoemission spectrometer with a mini Mott detector.

    PubMed

    Souma, S; Takayama, A; Sugawara, K; Sato, T; Takahashi, T

    2010-09-01

    We have developed an ultrahigh-resolution spin-resolved photoemission spectrometer with a highly efficient mini Mott detector and an intense xenon plasma discharge lamp. The spectrometer achieves the energy resolutions of 0.9 and 8 meV for non-spin-resolved and spin-resolved modes, respectively. Three-dimensional spin-polarization is determined by using a 90° electron deflector situated before the Mott detector. The performance of spectrometer is demonstrated by observation of a clear Rashba splitting of the Bi(111) surface states.

  17. Geometry-induced phase transition from a bosonic superfluid to a Mott insulator

    NASA Astrophysics Data System (ADS)

    Barter, Thomas; Thomas, Claire; Leung, Tsz Him; Okano, Masayuki; Stamper-Kurn, Dan

    2016-05-01

    We describe a preliminary characterization of the superfluid and Mott insulating phases of ultracold Rb 87 bosonic atoms in a two-dimensional optical superlattice with tunable lattice geometry. By smoothly changing the lattice structure from the triangular to kagome geometries while maintaining near-constant tunneling and interaction energies, we observe a geometry-induced phase transition from the superfluid to the Mott-insulating state. We characterize the superfluid by measurements of the coherent population fraction in time of flight, and find that the superfluid is less robust in the kagome geometry than in the triangular lattice, owing to the lower its lower coordination number.

  18. Thermodynamics versus Local Density Fluctuations in the Metal-Mott-Insulator Crossover

    NASA Astrophysics Data System (ADS)

    Drewes, J. H.; Cocchi, E.; Miller, L. A.; Chan, C. F.; Pertot, D.; Brennecke, F.; Köhl, M.

    2016-09-01

    The crossover between a metal and a Mott insulator leads to a localization of fermions from delocalized Bloch states to localized states. We experimentally study this crossover using fermionic atoms in an optical lattice by measuring thermodynamic and local (on-site) density correlations. In the metallic phase at incommensurable filling we observe the violation of the local fluctuation-dissipation theorem indicating that the thermodynamics of the system cannot be characterized by local observables alone. In contrast, in the Mott insulator we observe the convergence of local and thermodynamic fluctuations indicating the absence of long-range density-density correlations.

  19. Ultrahigh-resolution spin-resolved photoemission spectrometer with a mini Mott detector

    SciTech Connect

    Souma, S.; Sugawara, K.; Takayama, A.; Sato, T.; Takahashi, T.

    2010-09-15

    We have developed an ultrahigh-resolution spin-resolved photoemission spectrometer with a highly efficient mini Mott detector and an intense xenon plasma discharge lamp. The spectrometer achieves the energy resolutions of 0.9 and 8 meV for non-spin-resolved and spin-resolved modes, respectively. Three-dimensional spin-polarization is determined by using a 90 deg. electron deflector situated before the Mott detector. The performance of spectrometer is demonstrated by observation of a clear Rashba splitting of the Bi(111) surface states.

  20. Strongly correlated superconductivity and pseudogap phase near a multiband Mott insulator.

    PubMed

    Capone, Massimo; Fabrizio, Michele; Castellani, Claudio; Tosatti, Erio

    2004-07-23

    Near a Mott transition, strong electron correlations may enhance Cooper pairing. This is demonstrated in the dynamical mean field theory solution of a twofold-orbital degenerate Hubbard model with an inverted on-site Hund rule exchange, favoring local spin-singlet configurations. Close to the Mott insulator (which here is a local version of a valence bond insulator) a pseudogap non-Fermi-liquid metal, a superconductor, and a normal metal appear, in striking similarity with the physics of cuprates. The strongly correlated s-wave superconducting state has a larger Drude weight than the corresponding normal state. The role of the impurity Kondo problem is underscored.

  1. Magnetic properties in the Mott-insulating iron oxychalcogenides La2 O 2 Fe 2 OSe 2

    NASA Astrophysics Data System (ADS)

    Zhu, Jian-Xin; Yu, Rong; Si, Qimiao

    2011-03-01

    The role of electron correlation and magnetism in high-temperature superconductivity of the iron pnictides has been a topic of discussion. It has also motivated interest to compare related compounds with the iron pnictides and chalcogenides. Recently both electronic structure calculations and experimental measurements have indicated that the iron oxychalcogenides La 2 O2 Fe 2 OSe 2 , which contains an Fe square lattice with an enlarged unit cell, has a larger U/t and is a Mott insulator. We focus here on the understanding of the magnetism of this system. Within the density functional theory, we consider the magnetic phase diagram. Using an effective frustrating spin-exchange model in a doubled checker-board lattice, we study the magnetic excitation spectrum. Our theoretical results are compared with the emerging elastic and inelastic neutron scattering data in this compound. This work was supported by the NNSA of the U.S. DOE at LANL under Contract No. DE-AC52-06NA25396 (J.X.Z), the NSF Grant No. DMR-0706625, the Robert A. Welch Foundation Grant No. C-1411, and the W. M. Keck Foundation (R.Y. and Q.S.).

  2. Weak magnetism and the Mott state of vanadium in superconducting Sr2VO3FeAs

    NASA Astrophysics Data System (ADS)

    Hummel, Franziska; Su, Yixi; Senyshyn, Anatoliy; Johrendt, Dirk

    2013-10-01

    We report neutron-scattering data and DFT calculations of the stoichiometric iron-arsenide superconductor Sr2VO3FeAs. Rietveld refinements of neutron powder patterns confirm the ideal composition without oxygen deficiencies. Experiments with polarized neutrons prove weak magnetic ordering in the V sublattice of Sr2VO3FeAs at ≈ 45 K with a probable propagation vector q = ((1)/(8),(1)/(8),0). The ordered moment of ≈ 0.1 μB is too small to remove the V 3d bands from the Fermi level by magnetic exchange splitting and much smaller than predicted from a recent LDA+U study. By using DFT calculations with a GGA+EECE functional we find the typical quasinested Fermi surface even without magnetic moment. From this we conclude that the V atoms are in a Mott state, where the electronic correlations are dominated by on-site Coulomb repulsion which shifts the V 3d states away from the Fermi energy. Our results are consistent with photoemission data and explain comprehensively why Sr2VO3FeAs is a typical iron-arsenide superconductor in spite of the partially filled V 3d shell.

  3. Volume-wise destruction of the antiferromagnetic Mott insulating state through quantum tuning.

    PubMed

    Frandsen, Benjamin A; Liu, Lian; Cheung, Sky C; Guguchia, Zurab; Khasanov, Rustem; Morenzoni, Elvezio; Munsie, Timothy J S; Hallas, Alannah M; Wilson, Murray N; Cai, Yipeng; Luke, Graeme M; Chen, Bijuan; Li, Wenmin; Jin, Changqing; Ding, Cui; Guo, Shengli; Ning, Fanlong; Ito, Takashi U; Higemoto, Wataru; Billinge, Simon J L; Sakamoto, Shoya; Fujimori, Atsushi; Murakami, Taito; Kageyama, Hiroshi; Alonso, Jose Antonio; Kotliar, Gabriel; Imada, Masatoshi; Uemura, Yasutomo J

    2016-01-01

    RENiO3 (RE=rare-earth element) and V2O3 are archetypal Mott insulator systems. When tuned by chemical substitution (RENiO3) or pressure (V2O3), they exhibit a quantum phase transition (QPT) between an antiferromagnetic Mott insulating state and a paramagnetic metallic state. Because novel physics often appears near a Mott QPT, the details of this transition, such as whether it is first or second order, are important. Here, we demonstrate through muon spin relaxation/rotation (μSR) experiments that the QPT in RENiO3 and V2O3 is first order: the magnetically ordered volume fraction decreases to zero at the QPT, resulting in a broad region of intrinsic phase separation, while the ordered magnetic moment retains its full value until it is suddenly destroyed at the QPT. These findings bring to light a surprising universality of the pressure-driven Mott transition, revealing the importance of phase separation and calling for further investigation into the nature of quantum fluctuations underlying the transition. PMID:27531192

  4. Coulomb Liquid Phases of Bosonic Cluster Mott Insulators on a Pyrochlore Lattice.

    PubMed

    Lv, Jian-Ping; Chen, Gang; Deng, Youjin; Meng, Zi Yang

    2015-07-17

    Employing large-scale quantum Monte Carlo simulations, we reveal the full phase diagram of the extended Hubbard model of hard-core bosons on the pyrochlore lattice with partial fillings. When the intersite repulsion is dominant, the system is in a cluster Mott insulator phase with an integer number of bosons localized inside the tetrahedral units of the pyrochlore lattice. We show that the full phase diagram contains three cluster Mott insulator phases with 1/4, 1/2, and 3/4 boson fillings, respectively. We further demonstrate that all three cluster Mott insulators are Coulomb liquid phases and its low-energy property is described by the emergent compact U(1) quantum electrodynamics. In addition to measuring the specific heat and entropy of the cluster Mott insulators, we investigate the correlation function of the emergent electric field and verify it is consistent with the compact U(1) quantum electrodynamics description. Our result sheds light on the magnetic properties of various pyrochlore systems, as well as the charge physics of the cluster magnets.

  5. Promising Breakthroughs: Initial Results of the Charles Stewart Mott Foundation's Breaking Through Initiative. In Brief

    ERIC Educational Resources Information Center

    Bragg, Debra D.; Barnett, Elisabeth A.

    2008-01-01

    The Breaking Through (BT) initiative of the Charles Stewart Mott Foundation seeks to prepare low-skilled adults, adult learners who are below college-level in reading, writing and/or mathematics, often lacking a high school diploma, and frequently low-income, to be successful in college and the labor market by strengthening and expanding policies…

  6. Flat-Band Potential of a Semiconductor: Using the Mott-Schottky Equation

    ERIC Educational Resources Information Center

    Gelderman, K.; L. Lee; Donne, S. W.

    2007-01-01

    An experiment is suitable for fourth-year undergraduate and graduate students in which the nature of the semiconductor materials through determination of flat-band potential using the Mott-Schottky equation is explored. The experiment confirms the soundness of the technique.

  7. Volume-wise destruction of the antiferromagnetic Mott insulating state through quantum tuning

    PubMed Central

    Frandsen, Benjamin A.; Liu, Lian; Cheung, Sky C.; Guguchia, Zurab; Khasanov, Rustem; Morenzoni, Elvezio; Munsie, Timothy J. S.; Hallas, Alannah M.; Wilson, Murray N.; Cai, Yipeng; Luke, Graeme M.; Chen, Bijuan; Li, Wenmin; Jin, Changqing; Ding, Cui; Guo, Shengli; Ning, Fanlong; Ito, Takashi U.; Higemoto, Wataru; Billinge, Simon J. L.; Sakamoto, Shoya; Fujimori, Atsushi; Murakami, Taito; Kageyama, Hiroshi; Alonso, Jose Antonio; Kotliar, Gabriel; Imada, Masatoshi; Uemura, Yasutomo J.

    2016-01-01

    RENiO3 (RE=rare-earth element) and V2O3 are archetypal Mott insulator systems. When tuned by chemical substitution (RENiO3) or pressure (V2O3), they exhibit a quantum phase transition (QPT) between an antiferromagnetic Mott insulating state and a paramagnetic metallic state. Because novel physics often appears near a Mott QPT, the details of this transition, such as whether it is first or second order, are important. Here, we demonstrate through muon spin relaxation/rotation (μSR) experiments that the QPT in RENiO3 and V2O3 is first order: the magnetically ordered volume fraction decreases to zero at the QPT, resulting in a broad region of intrinsic phase separation, while the ordered magnetic moment retains its full value until it is suddenly destroyed at the QPT. These findings bring to light a surprising universality of the pressure-driven Mott transition, revealing the importance of phase separation and calling for further investigation into the nature of quantum fluctuations underlying the transition. PMID:27531192

  8. Volume-wise destruction of the antiferromagnetic Mott insulating state through quantum tuning

    NASA Astrophysics Data System (ADS)

    Frandsen, Benjamin A.; Liu, Lian; Cheung, Sky C.; Guguchia, Zurab; Khasanov, Rustem; Morenzoni, Elvezio; Munsie, Timothy J. S.; Hallas, Alannah M.; Wilson, Murray N.; Cai, Yipeng; Luke, Graeme M.; Chen, Bijuan; Li, Wenmin; Jin, Changqing; Ding, Cui; Guo, Shengli; Ning, Fanlong; Ito, Takashi U.; Higemoto, Wataru; Billinge, Simon J. L.; Sakamoto, Shoya; Fujimori, Atsushi; Murakami, Taito; Kageyama, Hiroshi; Alonso, Jose Antonio; Kotliar, Gabriel; Imada, Masatoshi; Uemura, Yasutomo J.

    2016-08-01

    RENiO3 (RE=rare-earth element) and V2O3 are archetypal Mott insulator systems. When tuned by chemical substitution (RENiO3) or pressure (V2O3), they exhibit a quantum phase transition (QPT) between an antiferromagnetic Mott insulating state and a paramagnetic metallic state. Because novel physics often appears near a Mott QPT, the details of this transition, such as whether it is first or second order, are important. Here, we demonstrate through muon spin relaxation/rotation (μSR) experiments that the QPT in RENiO3 and V2O3 is first order: the magnetically ordered volume fraction decreases to zero at the QPT, resulting in a broad region of intrinsic phase separation, while the ordered magnetic moment retains its full value until it is suddenly destroyed at the QPT. These findings bring to light a surprising universality of the pressure-driven Mott transition, revealing the importance of phase separation and calling for further investigation into the nature of quantum fluctuations underlying the transition.

  9. Coulomb Liquid Phases of Bosonic Cluster Mott Insulators on a Pyrochlore Lattice.

    PubMed

    Lv, Jian-Ping; Chen, Gang; Deng, Youjin; Meng, Zi Yang

    2015-07-17

    Employing large-scale quantum Monte Carlo simulations, we reveal the full phase diagram of the extended Hubbard model of hard-core bosons on the pyrochlore lattice with partial fillings. When the intersite repulsion is dominant, the system is in a cluster Mott insulator phase with an integer number of bosons localized inside the tetrahedral units of the pyrochlore lattice. We show that the full phase diagram contains three cluster Mott insulator phases with 1/4, 1/2, and 3/4 boson fillings, respectively. We further demonstrate that all three cluster Mott insulators are Coulomb liquid phases and its low-energy property is described by the emergent compact U(1) quantum electrodynamics. In addition to measuring the specific heat and entropy of the cluster Mott insulators, we investigate the correlation function of the emergent electric field and verify it is consistent with the compact U(1) quantum electrodynamics description. Our result sheds light on the magnetic properties of various pyrochlore systems, as well as the charge physics of the cluster magnets. PMID:26230823

  10. Volume-wise destruction of the antiferromagnetic Mott insulating state through quantum tuning

    DOE PAGESBeta

    B. A. Frandsen; Liu, L.; Cheung, S. C.; Guguchia, Z.; Khasanov, R.; Morenzoni, E.; Munsie, T. J.S.; Hallas, A. M.; Wilson, M. N.; Cai, Y.; et al

    2016-08-17

    RENiO3 (RE=rare-earth element) and V2O3 are archetypal Mott insulator systems. When tuned by chemical substitution (RENiO3) or pressure (V2O3), they exhibit a quantum phase transition (QPT) between an antiferromagnetic Mott insulating state and a paramagnetic metallic state. Because novel physics often appears near a Mott QPT, the details of this transition, such as whether it is first or second order, are important. Here, we demonstrate through muon spin relaxation/rotation (μSR) experiments that the QPT in RENiO3 and V2O3 is first order: the magnetically ordered volume fraction decreases to zero at the QPT, resulting in a broad region of intrinsic phasemore » separation, while the ordered magnetic moment retains its full value until it is suddenly destroyed at the QPT. These findings bring to light a surprising universality of the pressure-driven Mott transition, revealing the importance of phase separation and calling for further investigation into the nature of quantum fluctuations underlying the transition.« less

  11. Position Paper on International Studies Program at C. S. Mott Community College.

    ERIC Educational Resources Information Center

    Joseph, Wise B.

    This descriptive report outlines the history and operation of the International Studies Program at Charles Stewart Mott Community College (MCC). First, introductory material discusses the growing importance of international studies in the nation's community colleges. Next, the need for an international studies and international trade program at…

  12. Device Performance of the Mott Insulator LaVO3 as a Photovoltaic Material

    NASA Astrophysics Data System (ADS)

    Wang, Lingfei; Li, Yongfeng; Bera, Ashok; Ma, Chun; Jin, Feng; Yuan, Kaidi; Yin, Wanjian; David, Adrian; Chen, Wei; Wu, Wenbin; Prellier, Wilfrid; Wei, Suhuai; Wu, Tom

    2015-06-01

    Searching for solar-absorbing materials containing earth-abundant elements with chemical stability is of critical importance for advancing photovoltaic technologies. Mott insulators have been theoretically proposed as potential photovoltaic materials. In this paper, we evaluate their performance in solar cells by exploring the photovoltaic properties of Mott insulator LaVO3 (LVO). LVO films show an indirect band gap of 1.08 eV as well as strong light absorption over a wide wavelength range in the solar spectrum. First-principles calculations on the band structure of LVO further reveal that the d -d transitions within the upper and lower Mott-Hubbard bands and p -d transitions between the O 2 p and V 3 d band contribute to the absorption in visible and ultraviolet ranges, respectively. Transport measurements indicate strong carrier trapping and the formation of polarons in LVO. To utilize the strong light absorption of LVO and to overcome its poor carrier transport, we incorporate it as a light absorber in solar cells in conjunction with carrier transporters and evaluate its device performance. Our complementary experimental and theoretical results on such prototypical solar cells made of Mott-Hubbard transition-metal oxides pave the road for developing light-absorbing materials and photovoltaic devices based on strongly correlated electrons.

  13. Time-dependent Mott transition in the periodic Anderson model with nonlocal hybridization

    NASA Astrophysics Data System (ADS)

    Hofmann, Felix; Potthoff, Michael

    2016-08-01

    The time-dependent Mott transition in a periodic Anderson model with off-site, nearest-neighbor hybridization is studied within the framework of nonequilibrium self-energy functional theory. Using the two-site dynamical-impurity approximation, we compute the real-time dynamics of the optimal variational parameter and of different observables initiated by sudden quenches of the Hubbard-U and identify the critical interaction. The time-dependent transition is orbital selective, i.e., in the final state, reached in the long-time limit after the quench to the critical interaction, the Mott gap opens in the spectral function of the localized orbitals only. We discuss the dependence of the critical interaction and of the final-state effective temperature on the hybridization strength and point out the various similarities between the nonequilibrium and the equilibrium Mott transition. It is shown that these can also be smoothly connected to each other by increasing the duration of a U-ramp from a sudden quench to a quasi-static process. The physics found for the model with off-site hybridization is compared with the dynamical Mott transition in the single-orbital Hubbard model and with the dynamical crossover found for the real-time dynamics of the conventional Anderson lattice with on-site hybridization.

  14. Volume-wise destruction of the antiferromagnetic Mott insulating state through quantum tuning.

    PubMed

    Frandsen, Benjamin A; Liu, Lian; Cheung, Sky C; Guguchia, Zurab; Khasanov, Rustem; Morenzoni, Elvezio; Munsie, Timothy J S; Hallas, Alannah M; Wilson, Murray N; Cai, Yipeng; Luke, Graeme M; Chen, Bijuan; Li, Wenmin; Jin, Changqing; Ding, Cui; Guo, Shengli; Ning, Fanlong; Ito, Takashi U; Higemoto, Wataru; Billinge, Simon J L; Sakamoto, Shoya; Fujimori, Atsushi; Murakami, Taito; Kageyama, Hiroshi; Alonso, Jose Antonio; Kotliar, Gabriel; Imada, Masatoshi; Uemura, Yasutomo J

    2016-08-17

    RENiO3 (RE=rare-earth element) and V2O3 are archetypal Mott insulator systems. When tuned by chemical substitution (RENiO3) or pressure (V2O3), they exhibit a quantum phase transition (QPT) between an antiferromagnetic Mott insulating state and a paramagnetic metallic state. Because novel physics often appears near a Mott QPT, the details of this transition, such as whether it is first or second order, are important. Here, we demonstrate through muon spin relaxation/rotation (μSR) experiments that the QPT in RENiO3 and V2O3 is first order: the magnetically ordered volume fraction decreases to zero at the QPT, resulting in a broad region of intrinsic phase separation, while the ordered magnetic moment retains its full value until it is suddenly destroyed at the QPT. These findings bring to light a surprising universality of the pressure-driven Mott transition, revealing the importance of phase separation and calling for further investigation into the nature of quantum fluctuations underlying the transition.

  15. THE MOTT FOUNDATION CHILDREN'S HEALTH CENTER--THE WORLD OF STEPHEN SHAKER.

    ERIC Educational Resources Information Center

    Flint Board of Education, MI.

    THE C.S. MOTT FOUNDATION CHILDREN'S HEALTH CENTER WAS BUILT TO SERVE CHILDREN OF THOSE BORDERLINE FAMILIES WHOSE INCOMES PROHIBIT PRIVATE MEDICAL CARE YET MAKE THEM INELIGIBLE FOR DIRECT RELIEF OF ANY KIND. THE NEED FOR SUCH A CENTER WAS PROVED BY THE CHILDREN'S 18,000 VISITS ANNUALLY FOR HEALTH CARE. WHILE PROVIDING CARE FOR CHILDREN WAS THE MAIN…

  16. From Romantic Idealism to Enlightenment Rationalism: Lucretia Coffin Mott Responds to Richard Henry Dana, Sr.

    ERIC Educational Resources Information Center

    Sillars, Malcolm O.

    1995-01-01

    Suggests that the contrast between speeches by Richard Henry Dana Sr. and Lucretia Coffin Mott lies not only in their two views of the woman's place and role in society but also in the respective orientation toward Romantic idealism and Enlightenment rationalism. (TB)

  17. Experimental consequences of Mottness in high-temperature copper-oxide superconductors

    NASA Astrophysics Data System (ADS)

    Chakraborty, Shiladitya

    It has been more than two decades since the copper-oxide high temperature superconductors were discovered. However, building a satisfactory theoretical framework to study these compounds still remains one of the major challenges in condensed matter physics. In addition to the mechanism of superconductivity, understanding the properties of the normal state is a major puzzle in itself. As these materials are doped Mott insulators, the interaction between electrons is particularly strong. The strong electron correlations are responsible for the breakdown of Fermi-liquid behavior in the normal state. A variety of experimental probes reveal anomalous features in these materials. Such anomalies are reflected in the photoemission spectra as well as transport coefficients such as resistivity, optical conductivity, Hall coefficient, thermoelectric power etc. The objective of this dissertation is to understand the anomalous features as universal features of doped Mott insulators arising entirely as a consequence of strong electron correlations, using the two-dimensional square lattice Hubbard model as the model Hamiltonian. This dissertation is organized into eight chapters. Chapter 1 is an introductory chapter that discusses some key issues. A brief introduction to the superconducting cuprates and their anomalous physical properties is given. Also included is an outline on Mott insulators and the concept of Mottness. Chapter 2 contains a discussion on Cluster Dynamical Mean Field Theory (CDMFT), the principal numerical technique to be implemented in this dissertation. Chapter 3 describes the exact low-energy theory of doped Mott insulators, which largely provides a theoretical framework to this dissertation. In Chapter 4, we compute the spectral function of the two-dimensional Hubbard model using CDMFT and study the origin of the kink feature observed in the electron dispersion measured by ARPES (Angle Resolved Photoemission Spectroscopy). In Chapter 5, the origin of the

  18. Light scattering by ultracold atoms in an optical lattice

    SciTech Connect

    Rist, Stefan; Menotti, Chiara; Morigi, Giovanna

    2010-01-15

    We investigate theoretically light scattering of photons by ultracold atoms in an optical lattice in the linear regime. A full quantum theory for the atom-photon interactions is developed as a function of the atomic state in the lattice along the Mott-insulator-superfluid phase transition, and the photonic-scattering cross section is evaluated as a function of the energy and of the direction of emission. The predictions of this theory are compared with the theoretical results of a recent work on Bragg scattering in time-of-flight measurements [A.M. Rey et al., Phys. Rev. A 72, 023407 (2005)]. We show that, when performing Bragg spectroscopy with light scattering, the photon recoil gives rise to an additional atomic site-to-site hopping, which can interfere with ordinary tunneling of matter waves and can significantly affect the photonic-scattering cross section.

  19. Superconductivity and bandwidth-controlled Mott metal-insulator transition in 1T-TaS2-xSex

    NASA Astrophysics Data System (ADS)

    Ang, R.; Miyata, Y.; Ieki, E.; Nakayama, K.; Sato, T.; Liu, Y.; Lu, W. J.; Sun, Y. P.; Takahashi, T.

    2013-09-01

    We have performed high-resolution angle-resolved photoemission spectroscopy (ARPES) of layered chalcogenide 1T-TaS2-xSex to elucidate the electronic states especially relevant to the occurrence of superconductivity. We found a direct evidence for a Ta-5d-derived electron pocket associated with the superconductivity, which is fragile against a Mott-gap opening observed in the insulating ground state for S-rich samples. In particular, a strong electron-electron interaction-induced Mott gap driven by a Ta 5d orbital also exists in the metallic ground state for Se-rich samples, while finite ARPES intensity near the Fermi level likely originating from a Se 4p orbital survives, indicative of the orbital-selective nature of the Mott transition. Present results suggest that effective electron correlation and p-d hybridization play a crucial role to tune the superconductivity and Mott metal-insulator transition.

  20. Avalanche breakdown in GaTa4Se(8-x)Te(x) narrow-gap Mott insulators.

    PubMed

    Guiot, V; Cario, L; Janod, E; Corraze, B; Phuoc, V Ta; Rozenberg, M; Stoliar, P; Cren, T; Roditchev, D

    2013-01-01

    Mott transitions induced by strong electric fields are receiving growing interest. Recent theoretical proposals have focused on the Zener dielectric breakdown in Mott insulators. However, experimental studies are still too scarce to conclude about the mechanism. Here we report a study of the dielectric breakdown in the narrow-gap Mott insulators GaTa4Se(8-x)Te(x). We find that the I-V characteristics and the magnitude of the threshold electric field (Eth) do not correspond to a Zener breakdown, but rather to an avalanche breakdown. Eth increases as a power law of the Mott-Hubbard gap (Eg), in surprising agreement with the universal law Eth is proportional to Eg(2.5) reported for avalanche breakdown in semiconductors. However, the delay time for the avalanche that we observe in Mott insulators is over three orders of magnitude greater than in conventional semiconductors. Our results suggest that the electric field induces local insulator-to-metal Mott transitions that create conductive domains that grow to form filamentary paths across the sample.

  1. Strongly enhanced thermal transport in a lightly doped Mott insulator at low temperature.

    PubMed

    Zlatić, V; Freericks, J K

    2012-12-28

    We show how a lightly doped Mott insulator has hugely enhanced electronic thermal transport at low temperature. It displays universal behavior independent of the interaction strength when the carriers can be treated as nondegenerate fermions and a nonuniversal "crossover" region where the Lorenz number grows to large values, while still maintaining a large thermoelectric figure of merit. The electron dynamics are described by the Falicov-Kimball model which is solved for arbitrary large on-site correlation with a dynamical mean-field theory algorithm on a Bethe lattice. We show how these results are generic for lightly doped Mott insulators as long as the renormalized Fermi liquid scale is pushed to very low temperature and the system is not magnetically ordered.

  2. Novel P-T Phase Diagram of the Multiorbital Mott Insulator Sr2VO4.

    PubMed

    Karmakar, S; Malavi, Pallavi S

    2015-04-24

    The electrical and optical properties of the Mott insulator Sr2VO4 are investigated under high pressure on a phase pure polycrystalline sample. The system undergoes a pressure-driven insulator to metal transition (IMT) with a crossover between 20 and 24 GPa. The effect of pressure on the thermally driven electronic changes resulting from spin-orbital ordering transitions is studied. A multiorbital analysis of the low frequency optical conductivity spectra suggests a bandwidth-controlled and orbital selective nature of the Mott IMT transition. Dramatic enhancement of the low energy spectral weight in the high pressure correlated metallic phase is explained in terms of the formation of a quasiparticle peak in the spectral function of the narrow and degenerate d(yz,zx) orbitals. Our results overall establish a novel electronic phase diagram of tetragonal Sr2VO4.

  3. Finite mass enhancement across bandwidth controlled Mott transition in NiS2-xSex

    NASA Astrophysics Data System (ADS)

    Han, Garam; Kyung, W. S.; Kim, Y. K.; Cheng, C. M.; Tsuei, K. D.; Lee, K. D.; Hur, N.; Kim, H.-D.; Kim, C.

    One of the most important and still debated issues in the strongly correlated electron systems is on the metal insulator transition (MIT) mechanism. In the bandwidth controlled Mott transition (BCMT) scenario, which Mott originally proposed, MIT occurs through a mass divergence in which the effective mass of the quasi-particle (QP) diverges approaching the MIT. The interpretation is supported by dynamic mean field theory (DMFT) model calculations. However, few direct observations have been made yet due to various experimental restrictions. In this talk, I present systematic angle resolved photoemission studies on the MIT in NiS2-xSex, which is a well-known BCMT material. We observed not only the bandwidth shrinkage but also the coherent quasi-particle peak (QP) which is not of the surface origin. In addition, we experimentally showed the mass of the QP remains finite approaching the MIT. This work was supported by IBS-R009-D1.

  4. First-order melting of a weak spin-orbit mott insulator into a correlated metal

    DOE PAGESBeta

    Hogan, Tom; Yamani, Z.; Walkup, D.; Chen, Xiang; Dally, Rebecca; Ward, Thomas Zac; Dean, M. P. M.; Hill, John P.; Islam, Z.; Madhavan, Vidya; et al

    2015-06-25

    Herein, the electronic phase diagram of the weak spin-orbit Mott insulator (Sr1-xLax)3Ir2O7 is determined via an exhaustive experimental study. Upon doping electrons via La substitution, an immediate collapse in resistivity occurs along with a narrow regime of nanoscale phase separation comprised of antiferromagnetic, insulating regions and paramagnetic, metallic puddles persisting until x≈0.04. Continued electron doping results in an abrupt, first-order phase boundary where the Néel state is suppressed and a homogenous, correlated, metallic state appears with an enhanced spin susceptibility and local moments. In conclusion, as the metallic state is stabilized, a weak structural distortion develops and suggests a competingmore » instability with the parent spin-orbit Mott state.« less

  5. First-order melting of a weak spin-orbit mott insulator into a correlated metal

    SciTech Connect

    Hogan, Tom; Yamani, Z.; Walkup, D.; Chen, Xiang; Dally, Rebecca; Ward, Thomas Zac; Dean, M. P. M.; Hill, John P.; Islam, Z.; Madhavan, Vidya; Wilson, Stephen D.

    2015-06-25

    Herein, the electronic phase diagram of the weak spin-orbit Mott insulator (Sr1-xLax)3Ir2O7 is determined via an exhaustive experimental study. Upon doping electrons via La substitution, an immediate collapse in resistivity occurs along with a narrow regime of nanoscale phase separation comprised of antiferromagnetic, insulating regions and paramagnetic, metallic puddles persisting until x≈0.04. Continued electron doping results in an abrupt, first-order phase boundary where the Néel state is suppressed and a homogenous, correlated, metallic state appears with an enhanced spin susceptibility and local moments. In conclusion, as the metallic state is stabilized, a weak structural distortion develops and suggests a competing instability with the parent spin-orbit Mott state.

  6. Preparation and spectroscopy of a metastable Mott-insulator state with attractive interactions.

    PubMed

    Mark, M J; Haller, E; Lauber, K; Danzl, J G; Janisch, A; Büchler, H P; Daley, A J; Nägerl, H-C

    2012-05-25

    We prepare and study a metastable attractive Mott-insulator state formed with bosonic atoms in a three-dimensional optical lattice. Starting from a Mott insulator with Cs atoms at weak repulsive interactions, we use a magnetic Feshbach resonance to tune the interactions to large attractive values and produce a metastable state pinned by attractive interactions with a lifetime on the order of 10 s. We probe the (de)excitation spectrum via lattice modulation spectroscopy, measuring the interaction dependence of two- and three-body bound-state energies. As a result of increased on-site three-body loss we observe resonance broadening and suppression of tunneling processes that produce three-body occupation. PMID:23003276

  7. Extended dynamic Mott transition in the two-band Hubbard model out of equilibrium

    NASA Astrophysics Data System (ADS)

    Behrmann, Malte; Fabrizio, Michele; Lechermann, Frank

    2013-07-01

    We reformulate the time-dependent Gutzwiller approximation by M. Schiró and M. Fabrizio, [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.105.076401 105, 076401 (2010)] in the framework of slave-boson mean-field theory, which is used to investigate the dynamical Mott transition of the generic two-band Hubbard model at half filling upon an interaction quench. Interorbital fluctuations lead to notable changes with respect to the single-band case. The singular dynamical transition is replaced by a broad regime of long-lived fluctuations between metallic and insulating states, accompanied by intriguing precursor behavior. A mapping to a spin model proves helpful to analyze the different regions in terms of the evolution of an Ising-like order parameter. Contrary to the static case, singlet occupations remain vital in the Mott-insulating regime with finite Hund's exchange.

  8. First-Order Melting of a Weak Spin-Orbit Mott Insulator into a Correlated Metal.

    PubMed

    Hogan, Tom; Yamani, Z; Walkup, D; Chen, Xiang; Dally, Rebecca; Ward, Thomas Z; Dean, M P M; Hill, John; Islam, Z; Madhavan, Vidya; Wilson, Stephen D

    2015-06-26

    The electronic phase diagram of the weak spin-orbit Mott insulator (Sr(1-x)La(x))(3)Ir(2)O(7) is determined via an exhaustive experimental study. Upon doping electrons via La substitution, an immediate collapse in resistivity occurs along with a narrow regime of nanoscale phase separation comprised of antiferromagnetic, insulating regions and paramagnetic, metallic puddles persisting until x≈0.04. Continued electron doping results in an abrupt, first-order phase boundary where the Néel state is suppressed and a homogenous, correlated, metallic state appears with an enhanced spin susceptibility and local moments. As the metallic state is stabilized, a weak structural distortion develops and suggests a competing instability with the parent spin-orbit Mott state.

  9. Mott lobes evolution of the spin-1 Bose-Hubbard model

    NASA Astrophysics Data System (ADS)

    Hincapie-F, A. F.; Franco, R.; Silva-Valencia, J.

    2016-02-01

    We study spin-1 bosons confined in a one-dimensional optical lattice, taking into consideration both ferromagnetic and antiferromagnetic interaction. Using the density matrix renormalization group, we determine the phase diagram for the two firsts lobes and report the evolution of the first and second Mott lobes with respect to the spin-exchange interaction parameter (U 2). We determine that for the antiferromagnetic case, the first lobe is suppressed while the second grows as |U 2| increases. For the ferromagnetic case, the first and second Mott lobes are suppressed by the spin-exchange interaction parameter. We propose an expresion to describe the evolution of the critical point with the increase in |U 2| for both cases.

  10. Migration of Bosonic Particles across a Mott Insulator to a Superfluid Phase Interface

    NASA Astrophysics Data System (ADS)

    Hartmann, Michael J.; Plenio, Martin B.

    2008-02-01

    We consider a boundary between a Mott insulator and a superfluid region of a Bose-Hubbard model at unit filling. Initially both regions are decoupled and cooled to their respective ground states. We show that, after switching on a small tunneling rate between both regions, all particles of the Mott region migrate to the superfluid area. This migration takes place whenever the difference between the chemical potentials of both regions is less than the maximal energy of any eigenmode of the superfluid. We verify our results numerically with density matrix renormalization group simulations and explain them analytically with a master equation approximation, finding good agreement between both approaches. Finally we carry out a feasibility study for the observation of the effect in coupled arrays of microcavities and optical lattices.

  11. Absence of Asymptotic Freedom in Doped Mott Insulators: Breakdown of Strong Coupling Expansions

    NASA Astrophysics Data System (ADS)

    Phillips, Philip; Galanakis, Dimitrios; Stanescu, Tudor D.

    2004-12-01

    We show that doped Mott insulators such as the copper-oxide superconductors are asymptotically slaved in that the quasiparticle weight Z near half-filling depends critically on the existence of the high-energy scale set by the upper Hubbard band. In particular, near half-filling, the following dichotomy arises: Z≠0 when the high-energy scale is integrated out but Z=0 in the thermodynamic limit when it is retained. Slavery to the high-energy scale arises from quantum interference between electronic excitations across the Mott gap. Broad spectral features seen in photoemission in the normal state of the cuprates are argued to arise from high-energy slavery.

  12. Coexistence of Midgap Antiferromagnetic and Mott States in Undoped, Hole- and Electron-Doped Ambipolar Cuprates.

    PubMed

    Yin, Xinmao; Zeng, Shengwei; Das, Tanmoy; Baskaran, G; Asmara, Teguh Citra; Santoso, Iman; Yu, Xiaojiang; Diao, Caozheng; Yang, Ping; Breese, Mark B H; Venkatesan, T; Lin, Hsin; Ariando; Rusydi, Andrivo

    2016-05-13

    We report the first observation of the coexistence of a distinct midgap state and a Mott state in undoped and their evolution in electron and hole-doped ambipolar Y_{0.38}La_{0.62}(Ba_{0.82}La_{0.18})_{2}Cu_{3}O_{y} films using spectroscopic ellipsometry and x-ray absorption spectroscopies at the O K and Cu L_{3,2} edges. Supported by theoretical calculations, the midgap state is shown to originate from antiferromagnetic correlation. Surprisingly, while the magnetic state collapses and its correlation strength weakens with dopings, the Mott state in contrast moves toward a higher energy and its correlation strength increases. Our result provides important clues to the mechanism of electronic correlation strengths and superconductivity in cuprates. PMID:27232036

  13. Correlation-driven charge order at the interface between a Mott and a band insulator.

    PubMed

    Pentcheva, Rossitza; Pickett, Warren E

    2007-07-01

    To study digital Mott insulator LaTiO3 and band insulator SrTiO3 interfaces, we apply correlated band theory within the local density approximation including a Hubbard U to (n, m) multilayers, 1Mott insulating behavior of undistorted LaTiO3, the charge imbalance at the interface is found in all cases to be accommodated by disproportionation (Ti4++Ti3+), charge ordering, and Ti3+ dxy-orbital ordering, with antiferromagnetic exchange coupling between the spins in the interface layer. Lattice relaxations lead to conducting behavior by shifting (slightly but importantly) the lower Hubbard band, but the charge and orbital order is robust against relaxation. PMID:17678179

  14. Ultrafast and reversible control of the exchange interaction in Mott insulators

    PubMed Central

    Mentink, J. H.; Balzer, K.; Eckstein, M.

    2015-01-01

    The strongest interaction between microscopic spins in magnetic materials is the exchange interaction Jex. Therefore, ultrafast control of Jex holds the promise to control spins on ultimately fast timescales. We demonstrate that time-periodic modulation of the electronic structure by electric fields can be used to reversibly control Jex on ultrafast timescales in extended antiferromagnetic Mott insulators. In the regime of weak driving strength, we find that Jex can be enhanced and reduced for frequencies below and above the Mott gap, respectively. Moreover, for strong driving strength, even the sign of Jex can be reversed and we show that this causes time reversal of the associated quantum spin dynamics. These results suggest wide applications, not only to control magnetism in condensed matter systems, for example, via the excitation of spin resonances, but also to assess fundamental questions concerning the reversibility of the quantum many-body dynamics in cold atom systems. PMID:25819547

  15. Extension of the radiative lifetime of Wannier-Mott excitons in semiconductor nanoclusters

    SciTech Connect

    Kukushkin, V. A.

    2015-01-15

    The purpose of the study is to calculate the radiative lifetime of Wannier-Mott excitons in three-dimensional potential wells formed of direct-gap narrow-gap semiconductor nanoclusters in wide-gap semiconductors and assumed to be large compared to the exciton radius. Calculations are carried out for the InAs/GaAs heterosystem. It is shown that, as the nanocluster dimensions are reduced to values on the order of the exciton radius, the exciton radiative lifetime becomes several times longer compared to that in a homogeneous semiconductor. The increase in the radiative lifetime is more pronounced at low temperatures. Thus, it is established that the placement of Wannier-Mott excitons into direct-gap semiconductor nanoclusters, whose dimensions are of the order of the exciton radius, can be used for considerable extension of the exciton radiative lifetime.

  16. Bosons with Artificial Gauge Fields and Mott Physics on the Honeycomb Lattice

    NASA Astrophysics Data System (ADS)

    Vidanovic, Ivana; Petrescu, Alexandru; Le Hur, Karyn; Hofstetter, Walter

    2014-03-01

    We study bosons in the tight-binding model on the honeycomb lattice introduced by Haldane. We analyze the ground state topology and quasiparticle properties in the Mott phase by applying bosonic dynamical mean field theory, strong-coupling perturbation theory, exact diagonalization and numerical evaluations of sample Hall conductivity. The phase diagram also contains two different superfluid phases. The quasiparticle dynamics, number fluctuations, and local currents are measurable in cold atom experiments.

  17. Competing ground states of strongly correlated bosons in the Harper-Hofstadter-Mott model

    NASA Astrophysics Data System (ADS)

    Natu, Stefan S.; Mueller, Erich J.; Das Sarma, S.

    2016-06-01

    Using an efficient cluster approach, we study the physics of two-dimensional lattice bosons in a strong magnetic field in the regime where the tunneling is much weaker than the on-site interaction strength. We study both the dilute, hard-core bosons at filling factors much smaller than unity occupation per site and the physics in the vicinity of the superfluid-Mott lobes as the density is tuned away from unity. For hard-core bosons, we carry out extensive numerics for a fixed flux per plaquette ϕ =1 /5 and ϕ =1 /3 . At large flux, the lowest-energy state is a strongly correlated superfluid, analogous to He-4, in which the order parameter is dramatically suppressed, but nonzero. At filling factors ν =1 /2 ,1 , we find competing incompressible states which are metastable. These appear to be commensurate density wave states. For small flux, the situation is reversed and the ground state at ν =1 /2 is an incompressible density wave solid. Here, we find a metastable lattice supersolid phase, where superfluidity and density wave order coexist. We then perform careful numerical studies of the physics near the vicinity of the Mott lobes for ϕ =1 /2 and ϕ =1 /4 . At ϕ =1 /2 , the superfluid ground state has commensurate density wave order. At ϕ =1 /4 , incompressible phases appear outside the Mott lobes at densities n =1.125 and n =1.25 , corresponding to filling fractions ν =1 /2 and 1, respectively. These phases, which are absent in single-site mean-field theory, are metastable and have slightly higher energy than the superfluid, but the energy difference between them shrinks rapidly with increasing cluster size, suggestive of an incompressible ground state. We thus explore the interplay between Mott physics, magnetic Landau levels, and superfluidity, finding a rich phase diagram of competing compressible and incompressible states.

  18. NMR Study of the Superconducting Gap Variation near the Mott Transition in Cs3C60

    NASA Astrophysics Data System (ADS)

    Wzietek, P.; Mito, T.; Alloul, H.; Pontiroli, D.; Aramini, M.; Riccò, M.

    2014-02-01

    Former extensive studies of superconductivity in the A3C60 compounds, where A is an alkali metal, have led one to consider that Bardeen-Cooper-Schrieffer electron-phonon pairing prevails in those compounds, though the incidence of electronic Coulomb repulsion has been highly debated. The discovery of two isomeric fulleride compounds Cs3C60 which exhibit a transition with pressure from a Mott insulator (MI) to a superconducting (SC) state clearly reopens that question. Using pressure (p) as a single control parameter of the C60 balls lattice spacing, one can now study the progressive evolution of the SC properties when the electronic correlations are increased towards the critical pressure pc of the Mott transition. We have used C13 and Cs133 NMR measurements on the cubic phase A15-Cs3C60 just above pc=5.0(3) kbar, where the SC transition temperature Tc displays a dome shape with decreasing cell volume. From the T dependence below Tc of the nuclear spin lattice relaxation rate (T1)-1 we determine the electronic excitations in the SC state, that is 2Δ, the gap value. The latter is found to be largely enhanced with respect to the Bardeen-Cooper-Schrieffer value established in the case of dense A3C60 compounds. It even increases slightly with decreasing p towards pc, where Tc decreases on the SC dome, so that 2Δ /kBTc increases regularly upon approaching the Mott transition. These results bring clear evidence that the increasing correlations near the Mott transition are not significantly detrimental to superconductivity. They rather suggest that repulsive electron interactions might even reinforce elecron-phonon superconductivity, being then partly responsible for the large Tc values, as proposed by theoretical models taking the electronic correlations as a key ingredient.

  19. Transition from a Two-Dimensional Superfluid to a One-Dimensional Mott Insulator

    SciTech Connect

    Bergkvist, Sara; Rosengren, Anders; Saers, Robert; Lundh, Emil; Rehn, Magnus; Kastberg, Anders

    2007-09-14

    A two-dimensional system of atoms in an anisotropic optical lattice is studied theoretically. If the system is finite in one direction, it is shown to exhibit a transition between a two-dimensional superfluid and a one-dimensional Mott insulating chain of superfluid tubes. Monte Carlo simulations are consistent with the expectation that the phase transition is of Kosterlitz-Thouless type. The effect of the transition on experimental time-of-flight images is discussed.

  20. Random Field Driven Spatial Complexity at the Mott Transition in VO2

    NASA Astrophysics Data System (ADS)

    Carlson, Erica; Liu, Shuo; Phillabaum, Benjamin; Dahmen, Karin; Vidhyadhiraja, Narsimhamurthy; Qazilbash, Mumtaz; Basov, Dimitri

    We report the first application of critical cluster techniques to the Mott metal-insulator transition in vanadium dioxide. We show that the geometric properties of the metallic and insulating puddles observed by scanning near-field infrared microscopy are consistent with the system passing near criticality of the random field Ising model as temperature is varied. The resulting large barriers to equilibrium may be the source of the unusually robust hysteresis phenomena associated with the metal-insulator transition in this system.

  1. Microsphere plate detectors used with a compact Mott polarimeter for time-of-flight studies

    SciTech Connect

    Snell, G.; Viefhaus, J.; Dunning, F. B.; Berrah, N.

    2000-06-01

    A compact retarding-potential Mott polarimeter combined with microsphere plates (MSP) as electron detectors was built to perform spin-resolved time-of-flight electron spectroscopy. The comparison of the performance of MSP and channeltron detectors shows that the MSP detector has a better time resolution but a lower efficiency. The overall time resolution of the system was determined to be 350 ps using synchrotron radiation pulses. (c) 2000 American Institute of Physics.

  2. 5f-electron localization in the actinide metals: thorides, actinides and the Mott transition

    NASA Astrophysics Data System (ADS)

    Lawson, A. C.

    2016-03-01

    For the light actinides Ac-Cm, the numbers of localized and itinerant 5f-electrons are determined by comparing various estimates of the f-electron counts. At least one itinerant f-electron is found for each element, Pa-Cm. These results resolve certain disagreements among electron counts determined by different methods and are consistent with the Mott transition model and with the picture of the 5f-electrons' dual nature.

  3. Non-local order in Mott insulators, duality and Wilson loops

    SciTech Connect

    Rath, Steffen Patrick; Simeth, Wolfgang; Endres, Manuel; Zwerger, Wilhelm

    2013-07-15

    It is shown that the Mott insulating and superfluid phases of bosons in an optical lattice may be distinguished by a non-local ‘parity order parameter’ which is directly accessible via single site resolution imaging. In one dimension, the lattice Bose model is dual to a classical interface roughening problem. We use known exact results from the latter to prove that the parity order parameter exhibits long range order in the Mott insulating phase, consistent with recent experiments by Endres et al. [M. Endres, M. Cheneau, T. Fukuhara, C. Weitenberg, P. Schauß, C. Gross, L. Mazza, M.C. Bañuls, L. Pollet, I. Bloch, et al., Science 334 (2011) 200]. In two spatial dimensions, the parity order parameter can be expressed in terms of an equal time Wilson loop of a non-trivial U(1) gauge theory in 2+1 dimensions which exhibits a transition between a Coulomb and a confining phase. The negative logarithm of the parity order parameter obeys a perimeter law in the Mott insulator and is enhanced by a logarithmic factor in the superfluid. -- Highlights: •Number statistics of cold atoms in optical lattices show non-local correlations. •These correlations are measurable via single site resolution imaging. •Incompressible phases exhibit an area law in particle number fluctuations. •This leads to long-range parity order of Mott-insulators in one dimension. •Parity order in 2d is connected with a Wilson-loop in a lattice gauge theory.

  4. Mott Transitions and Staggered Orders in the Three-Component Fermionic System: Variational Cluster Approach

    NASA Astrophysics Data System (ADS)

    Hasunuma, Takumi; Kaneko, Tatsuya; Miyakoshi, Shohei; Ohta, Yukinori

    2016-07-01

    The variational cluster approximation is used to study the ground-state properties and single-particle spectra of the three-component fermionic Hubbard model defined on the two-dimensional square lattice at half filling. First, we show that either a paired Mott state or color-selective Mott state is realized in the paramagnetic system, depending on the anisotropy in the interaction strengths, except around the SU(3) symmetric point, where a paramagnetic metallic state is maintained. Then, by introducing Weiss fields to observe spontaneous symmetry breakings, we show that either a color-density-wave state or color-selective antiferromagnetic state is realized depending on the interaction anisotropy and that the first-order phase transition between these two states occurs at the SU(3) point. We moreover show that these staggered orders originate from the gain in potential energy (or Slater mechanism) near the SU(3) point but originate from the gain in kinetic energy (or Mott mechanism) when the interaction anisotropy is strong. The staggered orders near the SU(3) point disappear when the next-nearest-neighbor hopping parameters are introduced, indicating that these orders are fragile, protected only by the Fermi surface nesting.

  5. Identification of Mott insulators and Anderson insulators in self-assembled gold nanoparticles thin films.

    PubMed

    Jiang, Cheng-Wei; Ni, I-Chih; Tzeng, Shien-Der; Wu, Cen-Shawn; Kuo, Watson

    2014-06-01

    How the interparticle tunnelling affects the charge conduction of self-assembled gold nanoparticles is studied by three means: tuning the tunnel barrier width by different molecule modification and by substrate bending, and tuning the barrier height by high-dose electron beam exposure. All approaches indicate that the metal-Mott insulator transition is governed predominantly by the interparticle coupling strength, which can be quantified by the room temperature sheet resistance. The Hubbard gap, following the prediction of quantum fluctuation theory, reduces to zero rapidly as the sheet resistance decreases to the quantum resistance. At very low temperature, the fate of devices near the Mott transition depends on the strength of disorder. The charge conduction is from nearest-neighbour hopping to co-tunnelling between nanoparticles in Mott insulators whereas it is from variable-range hopping through charge puddles in Anderson insulators. When the two-dimensional nanoparticle network is under a unidirectional strain, the interparticle coupling becomes anisotropic so the average sheet resistance is required to describe the charge conduction.

  6. Strongly Correlated Superconductivity close to a Mott transition in orbitally degenerate models

    NASA Astrophysics Data System (ADS)

    Capone, Massimo; Fabrizio, Michele; Castellani, Claudio; Tosatti, Erio

    2004-03-01

    Recently a novel strongly correlated superconductivity (SCS) scenario has been proposed [1] which deals with the question whether and under which conditions Cooper-pairing may get enhanced by strong electron repulsion close to a Mott transition. The core of the SCS proposal is that the effective repulsion between quasiparticles vanishes close to the Mott transition, whereas any pairing attraction will remain unrenormalized if it acts inside the spin channel. This scenario was originally demonstrated through a Dynamical Mean Field Theory (DMFT) solution of a model for doped fullerenes, but it is believed to be far more general. Very recently, a twofold orbitally degenerate model with inverted Hund rule exchange has been proposed as a new candidate for SCS [2]. We report fresh DMFT work that fully confirms this expectation, and provides an extremely appealing phase diagram, where superconductivity arises by doping the Mott insulator, out of an unstable a pseudogapped metal, very much as it happens in cuprates. [1] M. Capone, M. Fabrizio, C. Castellani, and E. Tosatti, Science 296, 2364 (2002). [2] M. Fabrizio, A.F. Ho, L. De Leo, and G. Santoro, Phys. Rev. Lett., to appear; L. De Leo and M. Fabrizio, unpublished.

  7. Superconductivity close to the Mott state: From condensed-matter systems to superfluidity in optical lattices

    SciTech Connect

    Le Hur, Karyn Maurice Rice, T.

    2009-07-15

    Since the discovery of high-temperature superconductivity in 1986 by Bednorz and Mueller, great efforts have been devoted to finding out how and why it works. From the d-wave symmetry of the order parameter, the importance of antiferromagnetic fluctuations, and the presence of a mysterious pseudogap phase close to the Mott state, one can conclude that high-T{sub c} superconductors are clearly distinguishable from the well-understood BCS superconductors. The d-wave superconducting state can be understood through a Gutzwiller-type projected BCS wavefunction. In this review article, we revisit the Hubbard model at half-filling and focus on the emergence of exotic superconductivity with d-wave symmetry in the vicinity of the Mott state, starting from ladder systems and then studying the dimensional crossovers to higher dimensions. This allows to confirm that short-range antiferromagnetic fluctuations can mediate superconductivity with d-wave symmetry. Ladders are also nice prototype systems allowing to demonstrate the truncation of the Fermi surface and the emergence of a Resonating Valence Bond (RVB) state with preformed pairs in the vicinity of the Mott state. In two dimensions, a similar scenario emerges from renormalization group arguments. We also discuss theoretical predictions for the d-wave superconducting phase as well as the pseudogap phase, and address the crossover to the overdoped regime. Finally, cold atomic systems with tunable parameters also provide a complementary insight into this outstanding problem.

  8. Orbital-selective Mott phase of Cu-substituted iron-based superconductors

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Zhao, Yang-Yang; Song, Yun

    2016-07-01

    We study the phase transition in Cu-substituted iron-based superconductors with a new developed real-space Green’s function method. We find that Cu substitution has strong effect on the orbital-selective Mott transition introduced by the Hund’s rule coupling. The redistribution of the orbital occupancy which is caused by the increase of the Hund’s rule coupling, gives rise to the Mott-Hubbard metal-insulator transition in the half-filled d xy orbital. We also find that more and more electronic states appear inside that Mott gap of the d xy orbital with the increase of Cu substitution, and the in-gap states around the Fermi level are strongly localized at some specific lattice sites. Further, a distinctive phase diagram, obtained for the Cu-substituted Fe-based superconductors, displays an orbital-selective insulating phase, as a result of the cooperative effect of the Hund’s rule coupling and the impurity-induced disorder.

  9. Unquenched eg1 orbital moment in the Mott-insulating antiferromagnet KOsO4

    NASA Astrophysics Data System (ADS)

    Song, Young-Joon; Ahn, Kyo-Hoon; Lee, Kwan-Woo; Pickett, Warren E.

    2014-12-01

    Applying the correlated electronic structure method based on density functional theory plus the Hubbard U interaction, we have investigated the tetragonal scheelite structure Mott insulator KOsO4, whose eg1 configuration should be affected only slightly by spin-orbit coupling (SOC). The method reproduces the observed antiferromagnetic Mott-insulating state, populating the Os dz2 majority orbital. The quarter-filled eg manifold is characterized by a symmetry breaking due to the tetragonal structure, and the Os ion shows a crystal field splitting Δcf=1.7 eV from the t2 g complex, which is relatively small considering the high formal oxidation state Os 7 +. The small magnetocrystalline anisotropy before including correlation (i.e., in the metallic state) is increased by more than an order of magnitude in the Mott-insulating state, a result of a strong interplay between large SOC and a strong correlation. In contrast to conventional wisdom that the eg complex will not support orbital magnetism, we find that for the easy axis [100] direction the substantial Os orbital moment ML≈-0.2 μB compensates half of the Os spin moment MS=0.4 μB . The origin of the orbital moment is analyzed and understood in terms of additional spin-orbital lowering of symmetry, and beyond that due to structural distortion, for magnetization along [100]. Further interpretation is assisted by analysis of the spin density and the Wannier function with SOC included.

  10. Ellen N. La Motte: the making of a nurse, writer, and activist.

    PubMed

    Williams, Lea M

    2015-01-01

    This article examines the early career of Ellen N. La Motte (1873-1961) to trace how her training at the Johns Hopkins Training School for Nurses and years spent as a tuberculosis nurse in Baltimore shaped her perception of tuberculosis prevention and women's suffrage. Although studies of tuberculosis have frequently alluded to her work, no sustained biocritical discussion of her development as a nurse and scholar exists. Between 1902, when she graduated from nursing school, and 1914, the start of the Great War, La Motte published a textbook and dozens of articles in journals devoted to nursing and social reform and delivered many speeches at local, regional, and national meetings. In addition, as her reputation as an expert in the field of tuberculosis nursing grew, her advocacy for the vote for women increased, and she used her writing and speaking skills on behalf of the suffrage cause. This article assesses how the skills La Motte acquired during these years helped mold her into a successful and respected nurse, writer, and activist. PMID:25272476

  11. Nature of the magnetic correlations in photo-doped and chemically-doped spin-orbit Mott insulator Sr2IrO4

    NASA Astrophysics Data System (ADS)

    Dean, Mark P. M.

    In the iridates, competition between spin-orbit coupling, crystal field, and electronic correlation has lead to the observation of several novel states. Particularly notable is the spin-orbit Mott insulating state in Sr2IrO4 which has close analogies to the high temperature superconducting cuprates. This talk will describe the nature of the magnetic correlations in Sr2IrO4 and how the magnetic correlations can be modified by two different doping schemes. I will first describe doping via photo-excitation in which we use femtosecond infrared pulses to excite carriers across the Mott gap. After excitation, we probe the resulting magnetic state as a function of time delay using the first implementation of magnetic resonant inelastic X-ray scattering at a free electron laser. We find that the non-equilibrium state 2 ps after the excitation has strongly suppressed long-range magnetic order, but hosts photo-carriers that induce strong, non-thermal magnetic correlations. The magnetism recovers its two-dimensional in-plane Néel correlations on a timescale of a few ps, while the three-dimensional long range magnetic order is restored over a far longer, fluence-dependent timescale of a few 100 ps. In the second part of the talk I will describe chemical doping via Ir-Ru substitution. In this situation, we find that with increased Ru concentration, the dispersive magnetic excitations in the parent compound become almost momentum-independent, opening a magnetic gap > 150 meV. We attribute this gap to the combined effects of disorder and Ir-Ru interactions. Work performed at Brookhaven National Laboratory was supported by the US Department of Energy, Division of Materials Science, under Contract No. DE-AC02-98CH10886.

  12. Mean-field theory for the Mott-insulator-paired-superfluid phase transition in the two-species Bose-Hubbard model

    SciTech Connect

    Iskin, M.

    2010-11-15

    The standard mean-field theory for the Mott-insulator-superfluid phase transition is not sufficient to describe the Mott-insulator-paired-superfluid phase transition. Therefore, by restricting the two-species Bose-Hubbard Hamiltonian to the subspace of paired particles, and using perturbation theory, here we derive an analytic mean-field expression for the Mott-insulator-paired-superfluid transition boundary.

  13. Relativistic electron scattering from a freely movable proton in a strong laser field

    NASA Astrophysics Data System (ADS)

    Liu, Ai-Hua; Li, Shu-Min

    2014-11-01

    We study the electron scattering from the freely movable spin-1/2 proton in the presence of a linearly polarized laser field in the first Born approximation. The dressed state of the electron is described by a time-dependent wave function derived from a perturbation treatment (in a laser field). With the aid of numerical results we explore the dependencies of the differential cross section (DCS) on the electron-impact energy. Due to the mobility of the target, the DCS of this process is modified compared to the Mott scattering, especially in large scattering angles.

  14. Large Fermi Surface of Heavy Electrons at the Border of Mott Insulating State in NiS2

    DOE PAGESBeta

    Friedemann, S.; Chang, H.; Gamża, M. B.; Reiss, P.; Chen, X.; Alireza, P.; Coniglio, W. A.; Graf, D.; Tozer, S.; Grosche, F. M.

    2016-05-12

    One early triumph of quantum physics is the explanation why some materials are metallic whereas others are insulating. While a treatment based on single electron states is correct for most materials this approach can fail spectacularly, when the electrostatic repulsion between electrons causes strong correlations. Not only can these favor new and subtle forms of matter, such as magnetism or superconductivity, they can even cause the electrons in a half-filled energy band to lock into position, producing a correlated, or Mott insulator. The transition into the Mott insulating state raises important fundamental questions. Foremost among these is the fate ofmore » the electronic Fermi surface and the associated charge carrier mass, as the Mott transition is approached. We report the first direct observation of the Fermi surface on the metallic side of a Mott insulating transition by high pressure quantum oscillatory measurements in NiS2. We find our results point at a large Fermi surface consistent with Luttinger's theorem and a strongly enhanced quasiparticle effective mass. These two findings are in line with central tenets of the Brinkman-Rice picture of the correlated metal near the Mott insulating state and rule out alternative scenarios in which the carrier concentration vanishes continuously at the metal-insulator transition.« less

  15. Three-dimensional dynamics of a fermionic Mott wedding-cake in clean and disordered optical lattices

    PubMed Central

    Kartsev, A.; Karlsson, D.; Privitera, A.; Verdozzi, C.

    2013-01-01

    Non-equilibrium quantum phenomena are ubiquitous in nature. Yet, theoretical predictions on the real-time dynamics of many-body quantum systems remain formidably challenging, especially for high dimensions, strong interactions or disordered samples. Here we consider a notable paradigm of strongly correlated Fermi systems, the Mott phase of the Hubbard model, in a setup resembling ultracold-gases experiments. We study the three-dimensional expansion of a cloud into an optical lattice after removing the confining potential. We use time-dependent density-functional theory combined with dynamical mean-field theory, considering interactions below and above the Mott threshold, as well as disorder effects. At strong coupling, we observe multiple timescales in the melting of the Mott wedding-cake structure, as the Mott plateau persist orders of magnitude longer than the band insulating core. We also show that disorder destabilises the Mott plateau and that, compared to a clean setup, localisation can decrease, creating an interesting dynamic crossover during the expansion. PMID:23999144

  16. Large Fermi Surface of Heavy Electrons at the Border of Mott Insulating State in NiS2

    PubMed Central

    Friedemann, S.; Chang, H.; Gamża, M. B.; Reiss, P.; Chen, X.; Alireza, P.; Coniglio, W. A.; Graf, D.; Tozer, S.; Grosche, F. M.

    2016-01-01

    One early triumph of quantum physics is the explanation why some materials are metallic whereas others are insulating. While a treatment based on single electron states is correct for most materials this approach can fail spectacularly, when the electrostatic repulsion between electrons causes strong correlations. Not only can these favor new and subtle forms of matter, such as magnetism or superconductivity, they can even cause the electrons in a half-filled energy band to lock into position, producing a correlated, or Mott insulator. The transition into the Mott insulating state raises important fundamental questions. Foremost among these is the fate of the electronic Fermi surface and the associated charge carrier mass, as the Mott transition is approached. We report the first direct observation of the Fermi surface on the metallic side of a Mott insulating transition by high pressure quantum oscillatory measurements in NiS2. Our results point at a large Fermi surface consistent with Luttinger’s theorem and a strongly enhanced quasiparticle effective mass. These two findings are in line with central tenets of the Brinkman-Rice picture of the correlated metal near the Mott insulating state and rule out alternative scenarios in which the carrier concentration vanishes continuously at the metal-insulator transition. PMID:27174799

  17. Large Fermi Surface of Heavy Electrons at the Border of Mott Insulating State in NiS2

    NASA Astrophysics Data System (ADS)

    Friedemann, S.; Chang, H.; Gamża, M. B.; Reiss, P.; Chen, X.; Alireza, P.; Coniglio, W. A.; Graf, D.; Tozer, S.; Grosche, F. M.

    2016-05-01

    One early triumph of quantum physics is the explanation why some materials are metallic whereas others are insulating. While a treatment based on single electron states is correct for most materials this approach can fail spectacularly, when the electrostatic repulsion between electrons causes strong correlations. Not only can these favor new and subtle forms of matter, such as magnetism or superconductivity, they can even cause the electrons in a half-filled energy band to lock into position, producing a correlated, or Mott insulator. The transition into the Mott insulating state raises important fundamental questions. Foremost among these is the fate of the electronic Fermi surface and the associated charge carrier mass, as the Mott transition is approached. We report the first direct observation of the Fermi surface on the metallic side of a Mott insulating transition by high pressure quantum oscillatory measurements in NiS2. Our results point at a large Fermi surface consistent with Luttinger’s theorem and a strongly enhanced quasiparticle effective mass. These two findings are in line with central tenets of the Brinkman-Rice picture of the correlated metal near the Mott insulating state and rule out alternative scenarios in which the carrier concentration vanishes continuously at the metal-insulator transition.

  18. Haldane-Hubbard Mott Insulator: From Tetrahedral Spin Crystal to Chiral Spin Liquid

    NASA Astrophysics Data System (ADS)

    Hickey, Ciaran; Cincio, Lukasz; Papic, Zlatko; Paramekanti, Arun

    Motivated by recent experimental realizations of artificial gauge fields in ultracold atoms, we study the honeycomb lattice Haldane-Hubbard Mott insulator of spin- 1 / 2 fermions using exact diagonalization and density matrix renormalization group methods. We show that this model exhibits various chiral magnetic orders including a wide regime of triple-Q tetrahedral order. Incorporating third-neighbor hopping frustrates and ultimately melts this tetrahedral spin crystal. From analyzing low energy spectra, many-body Chern numbers, entanglement spectra, and modular matrices, we identify the molten state as a chiral spin liquid with gapped semion excitations.

  19. Appearance of "fragile" Fermi liquids in finite-width Mott insulators sandwiched between metallic leads.

    PubMed

    Zenia, H; Freericks, J K; Krishnamurthy, H R; Pruschke, Th

    2009-09-11

    Using inhomogeneous dynamical mean-field theory, we show that the normal-metal proximity effect could force any finite number of Mott-insulating "barrier" planes sandwiched between semi-infinite metallic leads to become "fragile" Fermi liquids. They are fully Fermi-liquid-like at T=0, leading to a restoration of lattice periodicity at zero frequency, with a well-defined Fermi surface, and perfect (ballistic) conductivity. However, the Fermi-liquid character can rapidly disappear at finite omega, V, T, disorder, or magnetism, all of which restore the expected quantum tunneling regime, leading to fascinating possibilities for nonlinear response in devices.

  20. Mott insulators of ultracold fermionic alkaline Earth atoms: underconstrained magnetism and chiral spin liquid.

    PubMed

    Hermele, Michael; Gurarie, Victor; Rey, Ana Maria

    2009-09-25

    We study Mott insulators of fermionic alkaline earth atoms, described by Heisenberg spin models with enhanced SU(N) symmetry. In dramatic contrast to SU(2) magnetism, more than two spins are required to form a singlet. On the square lattice, the classical ground state is highly degenerate and magnetic order is thus unlikely. In a large-N limit, we find a chiral spin liquid ground state with topological order and Abelian fractional statistics. We discuss its experimental detection. Chiral spin liquids with non-Abelian anyons may also be realizable with alkaline earth atoms.

  1. Theory of the optical conductivity of spin liquid states in one-dimensional Mott insulators.

    PubMed

    Katsura, Hosho; Sato, Masahiro; Furuta, Takashi; Nagaosa, Naoto

    2009-10-23

    The low-energy dynamical optical response of dimerized and undimerized spin liquid states in a one-dimensional charge transfer Mott insulator is theoretically studied. An exact analysis is given for the low-energy asymptotic behavior using conformal field theory for the undimerized state. In the dimerized state, the infrared absorption due to the bound state of two solitons, i.e., the breather mode, is predicted with an accurate estimate for its oscillator strength, offering a way to detect experimentally the excited singlet state. The effects of external magnetic fields are also discussed.

  2. A simple metal-insulator criterion for the doped Mott-Hubbard materials

    NASA Astrophysics Data System (ADS)

    Gavrichkov, Vladimir A.

    2015-04-01

    A simple metal-insulator criterion for doped Mott-Hubbard materials has been derived. Its readings are closely related to the orbital and spin nature of the ground states of the unit cell. The available criterion readings (metal or insulator) in the paramagnetic phase reveal the possibility of the insulator state of doped materials with the forbidden first removal electron states. According to its physical meaning, the result is similar to the Wilson's criterion in itinerant electron systems. The application of the criterion to high-Tc cuprates is discussed.

  3. Sauter-Schwinger-like tunneling in tilted Bose-Hubbard lattices in the Mott phase

    NASA Astrophysics Data System (ADS)

    Queisser, Friedemann; Navez, Patrick; Schützhold, Ralf

    2012-03-01

    We study the Mott phase of the Bose-Hubbard model on a tilted lattice. On the (Gutzwiller) mean-field level, the tilt has no effect, but quantum fluctuations entail particle-hole pair creation via tunneling. For small potential gradients (long-wavelength limit), we derive a quantitative analogy to the Sauter-Schwinger effect, i.e., electron-positron pair creation out of the vacuum by an electric field. For large tilts, we obtain resonant tunneling reminiscent of Bloch oscillations.

  4. Antiferromagnetic resonance in the Mott insulator fcc-Cs3C60.

    PubMed

    Suzuki, Yuta; Shibasaki, Seiji; Kubozono, Yoshihiro; Kambe, Takashi

    2013-09-11

    The magnetic ground state of the fcc phase of the Mott insulator Cs3C60 was studied using a low-temperature electron spin resonance technique, and antiferromagnetic resonance (AFMR) below 1.57 K was directly observed at ambient pressure. The AFMR modes for the fcc phase of Cs3C60 were investigated using a conventional two-sublattice model with uniaxial anisotropy, and the spin-flop field was determined to be 4.7 kOe at 1.57 K. The static magnetic exchange interactions and anisotropy field for fcc-Cs3C60 were also estimated.

  5. Random Field Driven Spatial Complexity at the Mott Transition in VO2

    NASA Astrophysics Data System (ADS)

    Liu, Shuo; Phillabaum, B.; Carlson, E. W.; Dahmen, K. A.; Vidhyadhiraja, N. S.; Qazilbash, M. M.; Basov, D. N.

    2016-01-01

    We report the first application of critical cluster techniques to the Mott metal-insulator transition in vanadium dioxide. We show that the geometric universal properties of the metallic and insulating puddles observed by scanning near-field infrared microscopy are consistent with the system passing near criticality of the random field Ising model as temperature is varied. The resulting large barriers to equilibrium may be the source of the unusually robust hysteresis phenomena associated with the metal-insulator transition in this system.

  6. Phase boundary of the boson Mott insulator in a rotating optical lattice

    SciTech Connect

    Umucalilar, R. O.; Oktel, M. Oe.

    2007-11-15

    We consider the Bose-Hubbard model in a two-dimensional rotating optical lattice and investigate the consequences of the effective magnetic field created by rotation. Using a Gutzwiller-type variational wave function, we find an analytical expression for the Mott insulator (MI)-superfluid (SF) transition boundary in terms of the maximum eigenvalue of the Hofstadter butterfly. The dependence of phase boundary on the effective magnetic field is complex, reflecting the self-similar properties of the single particle energy spectrum. Finally, we argue that fractional quantum Hall phases exist close to the MI-SF transition boundaries, including MI states with particle densities greater than one.

  7. Observation of 2D Fermionic Mott Insulators of 40K with Single-Site Resolution

    NASA Astrophysics Data System (ADS)

    Cheuk, Lawrence W.; Nichols, Matthew A.; Lawrence, Katherine R.; Okan, Melih; Zhang, Hao; Zwierlein, Martin W.

    2016-06-01

    We report on the site-resolved observation of characteristic states of the two-dimensional repulsive Fermi-Hubbard model, using ultracold 40K atoms in an optical lattice. By varying the tunneling, interaction strength, and external confinement, we realize metallic, Mott-insulating, and band-insulating states. We directly measure the local moment, which quantifies the degree of on-site magnetization, as a function of temperature and chemical potential. Entropies per particle as low as 0.99 (6 )kB indicate that nearest-neighbor antiferromagnetic correlations should be detectable using spin-sensitive imaging.

  8. Thermometry and refrigeration in a two-component Mott insulator of ultracold atoms

    SciTech Connect

    Weld, David M.; Miyake, Hirokazu; Medley, Patrick; Pritchard, David E.; Ketterle, Wolfgang

    2010-11-15

    Interesting spin Hamiltonians can be realized with ultracold atoms in a two-component Mott insulator (2CMI) [Adv. Phys. 56, 243 (2007); Rev. Mod. Phys. 80, 885 (2008)]. It was recently demonstrated that the application of a magnetic field gradient to the 2CMI enables new techniques of thermometry [Phys. Rev. Lett. 103, 245301 (2009)] and adiabatic cooling [e-print arXiv:1006.4674]. Here we present a theoretical description which provides quantitative analysis of these two techniques. We show that adiabatic reduction of the field gradient is capable of cooling below the Curie or Neel temperature of certain spin-ordered phases.

  9. Ferromagnetism in the Mott insulator Ba2NaOsO6

    SciTech Connect

    Erickson, A.S.; Misra, S.; Miller, G.J.; Harrison, W.A.; Kim, J.M.; Fisher, I.R.; /Stanford U., Appl. Phys. Dept. /Stanford U., Geballe Lab.

    2010-01-15

    Results are presented of single crystal structural, thermodynamic, and reflectivity measurements of the double-perovskite Ba{sub 2}NaOsO{sub 6}. These characterize the material as a 5d1 ferromagnetic Mott insulator with an ordered moment of {approx} 0.2 {micro}B per formula unit and T{sub C} = 6.8(3) K. The magnetic entropy associated with this phase transition is close to Rln2, indicating that the quartet groundstate anticipated from consideration of the crystal structure is split, consistent with a scenario in which the ferromagnetism is associated with orbital ordering.

  10. Equations for the Cabrera-Mott kinetics of oxidation for spherical nanoparticles

    NASA Astrophysics Data System (ADS)

    Ermoline, Alexandre; Dreizin, Edward L.

    2011-03-01

    Equations describing formation of a spherical oxide shell according to the Cabrera-Mott mechanism are presented. Two different configurations of metal and oxidizer are considered: oxidation of a spherical metal particle in surrounding oxidizer, and reduction of a spherical oxide inclusion in a metal matrix. Equations for the former configuration were reported earlier but did not explicitly account for volume changes in the growing oxide shell and shrinking central core. For aluminum oxidation, the correction for these volume changes is significant for spherical particles with diameters less than 10 nm.

  11. Calculation of relativistic effects in sub Coulomb heavy ion scattering

    NASA Astrophysics Data System (ADS)

    Hencken, Kai; Trautmann, Dirk

    1991-06-01

    Relativistic corrections for the elastic scattering of heavy ions in the sub Coulomb regime are given. The case of two identical particles is treated especially. The deviation from the Rutherford (Mott) cross section is calculated by using the Todorov equation and the Darwin Hamiltonian, resp. It is shown, that both approches lead to the same results for small kinetic energies. Furthermore we discuss the applicability of the WKB method for calculating the phase shifts and the possibility of using a classical perturbative approach in the case of nonidentical particles.

  12. Doped Mott insulators in (111) bilayers of perovskite transition-metal oxides with a strong spin-orbit coupling.

    PubMed

    Okamoto, Satoshi

    2013-02-01

    The electronic properties of Mott insulators realized in (111) bilayers of perovskite transition-metal oxides are studied. The low-energy effective Hamiltonians for such Mott insulators are derived in the presence of a strong spin-orbit coupling. These models are characterized by the antiferromagnetic Heisenberg interaction and the anisotropic interaction whose form depends on the d orbital occupancy. From exact diagonalization analyses on finite clusters, the ground state phase diagrams are derived, including a Kitaev spin liquid phase in a narrow parameter regime for t(2g) systems. Slave-boson mean-field analyses indicate the possibility of novel superconducting states induced by carrier doping into the Mott-insulating parent systems, suggesting the present model systems as unique playgrounds for studying correlation-induced novel phenomena. Possible experimental realizations are also discussed.

  13. Interference of atomic levels and superfluid-Mott insulator phase transitions in a two-component Bose-Einstein condensate.

    PubMed

    Krutitsky, K V; Graham, R

    2003-12-12

    The superfluid-Mott insulator phase transition in a Bose-Einstein condensate of neutral atoms with doubly degenerate internal ground states in an optical lattice is theoretically investigated. The optical lattice is created by two counterpropagating linearly polarized laser beams with the angle theta between the polarization vectors (lin-angle-lin configuration). The phase diagram of the system and the critical values of the parameters are worked out. It is shown that the sign of the detuning plays an important role and that there is a strong suppression of the Mott transition in the case of blue detuning. Varying the laser intensity and/or the angle theta one can manipulate the Mott insulator to superfluid quantum phase transition as well as prepare the condensate in physically distinguishable "ferromagnetic" and "antiferromagnetic" superfluid states.

  14. Pressure-Induced Mott Transition Followed by a 24-K Superconducting Phase in BaFe2S3

    NASA Astrophysics Data System (ADS)

    Yamauchi, Touru; Hirata, Yasuyuki; Ueda, Yutaka; Ohgushi, Kenya

    2015-12-01

    We performed high-pressure study for a Mott insulator BaFe2S3 , by measuring dc resistivity and ac susceptibility up to 15 GPa. We found that the antiferromagnetic insulating state at the ambient pressure is transformed into a metallic state at the critical pressure, Pc=10 GPa , and the superconductivity with the optimum Tc=24 K emerges above Pc. Furthermore, we found that the metal-insulator transition (Mott transition) boundary terminates at a critical point around 10 GPa and 75 K. The obtained pressure-temperature (P -T ) phase diagram is similar to those of the organic and fullerene compounds; namely, BaFe2S3 is the first inorganic superconductor in the vicinity of bandwidth control type Mott transition.

  15. Doped Mott Insulators in (111) Bilayers of Perovskite Transition-Metal Oxides with a Strong Spin-Orbit Coupling

    SciTech Connect

    Okamoto, Satoshi

    2013-01-01

    The electronic properties of Mott insulators realized in (111) bilayers of perovskite transition-metal oxides are studied. The low-energy effective Hamiltonians for such Mott insulators are derived in the presence of a strong spin-orbit coupling. These models are characterized by the antiferromagnetic Heisenberg interaction and the anisotropic interaction whose form depends on the $d$ orbital occupancy. From exact diagonalization analyses on finite clusters, the ground state phase diagrams are derived, including a Kitaev spin liquid phase in a narrow parameter regime for $t_{2g}$ systems. Slave-boson mean-field analyses indicate the possibility of novel superconducting states induced by carrier doping into the Mott-insulating parent systems, suggesting the present model systems as unique playgrounds for studying correlation-induced novel phenomena. Possible experimental realizations are also discussed.

  16. Fabrication and Measurement of Electroluminescence and Electrical Properties of Organic Light-Emitting Diodes Containing Mott Insulator Nanocrystals.

    PubMed

    Nozoe, Soichiro; Kinoshita, Nobuaki; Matsuda, Masaki

    2016-04-01

    By using the short-time electrocrystallization technique, phthalocyanine (Pc)-based Mott insulator Co(Pc)(CN)2 . 2CHCl3 nanocrystals were fabricated and applied to organic light-emiting diodes (OLEDs). The fabricated device having the configuration ITO/Co(Pc)(CN)2 . 2CHCl3/Alq3/Al, in which ITO is indium-tin oxide and Alq3 is tris(8-hydroxyquinolinato)aluminum, showed clear emission from Alq3, suggesting the Mott insulator Co(Pc)(CN)2 . 2CHCl3 can work as useful hole-injection and transport material in OLEDs.

  17. Fabrication and Measurement of Electroluminescence and Electrical Properties of Organic Light-Emitting Diodes Containing Mott Insulator Nanocrystals.

    PubMed

    Nozoe, Soichiro; Kinoshita, Nobuaki; Matsuda, Masaki

    2016-04-01

    By using the short-time electrocrystallization technique, phthalocyanine (Pc)-based Mott insulator Co(Pc)(CN)2 . 2CHCl3 nanocrystals were fabricated and applied to organic light-emiting diodes (OLEDs). The fabricated device having the configuration ITO/Co(Pc)(CN)2 . 2CHCl3/Alq3/Al, in which ITO is indium-tin oxide and Alq3 is tris(8-hydroxyquinolinato)aluminum, showed clear emission from Alq3, suggesting the Mott insulator Co(Pc)(CN)2 . 2CHCl3 can work as useful hole-injection and transport material in OLEDs. PMID:27451640

  18. Strong-coupling approach to Mott transition of massless and massive Dirac fermions on honeycomb lattice

    NASA Astrophysics Data System (ADS)

    Adibi, Elaheh; Jafari, S. Akbar

    2016-02-01

    Phase transitions in the Hubbard model and ionic Hubbard model at half-filling on the honeycomb lattice are investigated in the strong-coupling perturbation theory which corresponds to an expansion in powers of the hopping t around the atomic limit. Within this formulation we find analytic expressions for the single-particle spectrum, whereby the calculation of the insulating gap is reduced to a simple root finding problem. This enables high-precision determination of the insulating gap that does not require any extrapolation procedure. The critical value of Mott transition on the honeycomb lattice is obtained to be Uc≈2.38 t . Studying the ionic Hubbard model at the lowest order, we find two insulating states, one with Mott character at large U and another with single-particle gap character at large ionic potential Δ . The present approach gives a critical gapless state at U =2 Δ at lowest order. By systematically improving on the perturbation expansion, the density of states around this critical gapless phase reduces.

  19. Unified understanding of superconductivity and Mott transition in alkali-doped fullerides from first principles.

    PubMed

    Nomura, Yusuke; Sakai, Shiro; Capone, Massimo; Arita, Ryotaro

    2015-08-01

    Alkali-doped fullerides A 3C60 (A = K, Rb, Cs) are surprising materials where conventional phonon-mediated superconductivity and unconventional Mott physics meet, leading to a remarkable phase diagram as a function of volume per C60 molecule. We address these materials with a state-of-the-art calculation, where we construct a realistic low-energy model from first principles without using a priori information other than the crystal structure and solve it with an accurate many-body theory. Remarkably, our scheme comprehensively reproduces the experimental phase diagram including the low-spin Mott-insulating phase next to the superconducting phase. More remarkably, the critical temperatures T c's calculated from first principles quantitatively reproduce the experimental values. The driving force behind the surprising phase diagram of A 3C60 is a subtle competition between Hund's coupling and Jahn-Teller phonons, which leads to an effectively inverted Hund's coupling. Our results establish that the fullerides are the first members of a novel class of molecular superconductors in which the multiorbital electronic correlations and phonons cooperate to reach high T c s-wave superconductivity.

  20. Dimensional crossover and cold-atom realization of topological Mott insulators.

    PubMed

    Scheurer, Mathias S; Rachel, Stephan; Orth, Peter P

    2015-02-11

    Interacting cold-atomic gases in optical lattices offer an experimental approach to outstanding problems of many body physics. One important example is the interplay of interaction and topology which promises to generate a variety of exotic phases such as the fractionalized Chern insulator or the topological Mott insulator. Both theoretically understanding these states of matter and finding suitable systems that host them have proven to be challenging problems. Here we propose a cold-atom setup where Hubbard on-site interactions give rise to spin liquid-like phases: weak and strong topological Mott insulators. They represent the celebrated paradigm of an interacting and topological quantum state with fractionalized spinon excitations that inherit the topology of the non-interacting system. Our proposal shall help to pave the way for a controlled experimental investigation of this exotic state of matter in optical lattices. Furthermore, it allows for the investigation of a dimensional crossover from a two-dimensional quantum spin Hall insulating phase to a three-dimensional strong topological insulator by tuning the hopping between the layers.

  1. Bias activated dielectric response of excitons and excitonic Mott transition in quantum confined lasers structures.

    NASA Astrophysics Data System (ADS)

    Bhunia, Amit; Bansal, Kanika; Datta, Shouvik; Alshammari, Marzook S.; Henini, Mohamed

    In contrast to the widely reported optical techniques, there are hardly any investigations on corresponding electrical signatures of condensed matter physics of excitonic phenomena. We studied small signal steady state capacitance response in III-V materials based multi quantum well (AlGaInP) and MBE grown quantum dot (InGaAs) laser diodes to identify signatures of excitonic presence. Conductance activation by forward bias was probed using frequency dependent differential capacitance response (fdC/df), which changes characteristically with the onset of light emission indicating the occurrence of negative activation energy. Our analysis shows that it is connected with a steady state population of exciton like bound states. Calculated average energy of this bound state matches well with the binding energy of weakly confined excitons in this type of structures. Further increase in charge injection decreases the differential capacitive response in AlGaInP based diodes, indicating a gradual Mott transition of excitonic states into electron hole plasma. This electrical description of excitonic Mott transition is fully supplemented by standard optical spectroscopic signatures of band gap renormalization and phase space filling effects.

  2. Charge-ordering cascade with spin-orbit Mott dimer states in metallic iridium ditelluride.

    PubMed

    Ko, K-T; Lee, H-H; Kim, D-H; Yang, J-J; Cheong, S-W; Eom, M J; Kim, J S; Gammag, R; Kim, K-S; Kim, H-S; Kim, T-H; Yeom, H-W; Koo, T-Y; Kim, H-D; Park, J-H

    2015-01-01

    Spin-orbit coupling results in technologically-crucial phenomena underlying magnetic devices like magnetic memories and energy-efficient motors. In heavy element materials, the strength of spin-orbit coupling becomes large to affect the overall electronic nature and induces novel states such as topological insulators and spin-orbit-integrated Mott states. Here we report an unprecedented charge-ordering cascade in IrTe2 without the loss of metallicity, which involves localized spin-orbit Mott states with diamagnetic Ir(4+)-Ir(4+) dimers. The cascade in cooling, uncompensated in heating, consists of first order-type consecutive transitions from a pure Ir(3+) phase to Ir(3+)-Ir(4+) charge-ordered phases, which originate from Ir 5d to Te 5p charge transfer involving anionic polymeric bond breaking. Considering that the system exhibits superconductivity with suppression of the charge order by doping, analogously to cuprates, these results provide a new electronic paradigm of localized charge-ordered states interacting with itinerant electrons through large spin-orbit coupling. PMID:26059464

  3. Ultra-fast photo-carrier relaxation in Mott insulators with short-range spin correlations

    PubMed Central

    Eckstein, Martin; Werner, Philipp

    2016-01-01

    Ultra-fast spectroscopy can reveal the interplay of charges with low energy degrees of freedom, which underlies the rich physics of correlated materials. As a potential glue for superconductivity, spin fluctuations in Mott insulators are of particular interest. A theoretical description of the coupled spin and charge degrees of freedom is challenging, because magnetic order is often only short-lived and short-ranged. In this work we theoretically investigate how the spin-charge interactions influence the relaxation of a two-dimensional Mott-Hubbard insulator after photo-excitation. We use a nonequilibrium variant of the dynamical cluster approximation, which, in contrast to single-site dynamical mean-field theory, captures the effect of short-range correlations. The relaxation time is found to scale with the strength of the nearest-neighbor spin correlations, and can be 10–20 fs in the cuprates. Increasing the temperature or excitation density decreases the spin correlations and thus implies longer relaxation times. This may help to distinguish the effect of spin-fluctuations on the charge relaxation from the influence of other bosonic modes in the solid. PMID:26883536

  4. Unified understanding of superconductivity and Mott transition in alkali-doped fullerides from first principles

    PubMed Central

    Nomura, Yusuke; Sakai, Shiro; Capone, Massimo; Arita, Ryotaro

    2015-01-01

    Alkali-doped fullerides A3C60 (A = K, Rb, Cs) are surprising materials where conventional phonon-mediated superconductivity and unconventional Mott physics meet, leading to a remarkable phase diagram as a function of volume per C60 molecule. We address these materials with a state-of-the-art calculation, where we construct a realistic low-energy model from first principles without using a priori information other than the crystal structure and solve it with an accurate many-body theory. Remarkably, our scheme comprehensively reproduces the experimental phase diagram including the low-spin Mott-insulating phase next to the superconducting phase. More remarkably, the critical temperatures Tc’s calculated from first principles quantitatively reproduce the experimental values. The driving force behind the surprising phase diagram of A3C60 is a subtle competition between Hund’s coupling and Jahn-Teller phonons, which leads to an effectively inverted Hund’s coupling. Our results establish that the fullerides are the first members of a novel class of molecular superconductors in which the multiorbital electronic correlations and phonons cooperate to reach high Tc s-wave superconductivity. PMID:26601242

  5. Quantum simulation of a topological Mott insulator with Rydberg atoms in a Lieb lattice

    NASA Astrophysics Data System (ADS)

    Dauphin, A.; Müller, M.; Martin-Delgado, M. A.

    2016-04-01

    We propose a realistic scheme to quantum simulate the so-far experimentally unobserved topological Mott insulator phase—an interaction-driven topological insulator—using cold atoms in an optical Lieb lattice. To this end, we study a system of spinless fermions in a Lieb lattice, exhibiting repulsive nearest- and next-to-nearest-neighbor interactions and derive the associated zero-temperature phase diagram within mean-field approximation. In particular, we analyze how the interactions can dynamically generate a charge density wave ordered, a nematic, and a topologically nontrivial quantum anomalous Hall phase. We characterize the topology of the different phases by the Chern number and discuss the possibility of phase coexistence. Based on the identified phases, we propose a realistic implementation of this model using cold Rydberg-dressed atoms in an optical lattice. The scheme, which allows one to access, in particular, the topological Mott insulator phase, robustly and independently of its exact position in parameter space, merely requires global, always-on off-resonant laser coupling to Rydberg states and is feasible with state-of-the-art experimental techniques that have already been demonstrated in the laboratory.

  6. Electrical permittivity driven metal-insulator transition in heterostructures of nonpolar Mott and band insulators

    NASA Astrophysics Data System (ADS)

    Omori, Yukiko; Rüegg, Andreas; Sigrist, Manfred

    2014-10-01

    Metallic interfaces between insulating perovskites are often observed in heterostructures combining polar and nonpolar materials. In these systems, the polar discontinuity across the interface may drive an electronic reconstruction inducing free carriers at the interface. Here, we theoretically show that a metallic interface between a Mott and a band insulator can also form in the absence of a polar discontinuity. The condition for the appearance of such a metallic state is consistent with the classical Mott criterion: the metallic state is stable if the screening length falls below the effective Bohr radius of a particle-hole pair. In this case, the metallic state bears a remarkable similarity to the one found in polar/nonpolar heterostructures. On the other hand, if the screening length approaches the size of the effective Bohr radius, particles and holes are bound to each other resulting in an overall insulating phase. We analyze this metal-insulator transition, which is tunable by the dielectric constant, in the framework of the slave-boson mean-field theory for a lattice model with both on-site and long-range Coulomb interactions. We discuss ground-state properties and transport coefficients, which we derive in the relaxation-time approximation. Interestingly, we find that the metal-insulator transition is accompanied by a strong enhancement of the Seebeck coefficient in the band-insulator region in the vicinity of the interface. The implications of our theoretical findings for various experimental systems such as nonpolar (110) interfaces are also discussed.

  7. Mott insulating states and quantum phase transitions of correlated SU(2 N ) Dirac fermions

    NASA Astrophysics Data System (ADS)

    Zhou, Zhichao; Wang, Da; Meng, Zi Yang; Wang, Yu; Wu, Congjun

    2016-06-01

    The interplay between charge and spin degrees of freedom in strongly correlated fermionic systems, in particular of Dirac fermions, is a long-standing problem in condensed matter physics. We investigate the competing orders in the half-filled SU (2 N ) Hubbard model on a honeycomb lattice, which can be accurately realized in optical lattices with ultracold large-spin alkaline-earth fermions. Employing large-scale projector determinant quantum Monte Carlo simulations, we have explored quantum phase transitions from the gapless Dirac semimetals to the gapped Mott insulating phases in the SU(4) and SU(6) cases. Both of these Mott insulating states are found to be columnar valence bond solid (cVBS) and to be absent of the antiferromagnetic Néel ordering and the loop current ordering. Inside the cVBS phases, the dimer ordering is enhanced by increasing fermion components and behaves nonmonotonically as the interaction strength increases. Although the transitions generally should be of first order due to a cubic invariance possessed by the cVBS order, the coupling to gapless Dirac fermions can soften the transitions to second order through a nonanalytic term in the free energy. Our simulations provide important guidance for the experimental explorations of novel states of matter with ultracold alkaline-earth fermions.

  8. Nonequilibrium self-energy functional approach to the dynamical Mott transition

    NASA Astrophysics Data System (ADS)

    Hofmann, Felix; Eckstein, Martin; Potthoff, Michael

    2016-06-01

    The real-time dynamics of the Fermi-Hubbard model, driven out of equilibrium by quenching or ramping the interaction parameter, is studied within the framework of the nonequilibrium self-energy functional theory. A dynamical impurity approximation with a single auxiliary bath site is considered as a reference system, and the time-dependent hybridization is optimized as prescribed by the variational principle. The dynamical two-site approximation turns out to be useful to study the real-time dynamics on short and intermediate time scales. Depending on the strength of the interaction in the final state, two qualitatively different response regimes are observed. For both weak and strong couplings, qualitative agreement with previous results of nonequilibrium dynamical mean-field theory is found. The two regimes are sharply separated by a critical point at which the low-energy bath degree of freedom decouples in the course of time. We trace the dependence of the critical interaction of the dynamical Mott transition on the duration of the interaction ramp from sudden quenches to adiabatic dynamics and therewith link the dynamical to the equilibrium Mott transition.

  9. Dimensional crossover and cold-atom realization of topological Mott insulators

    PubMed Central

    Scheurer, Mathias S.; Rachel, Stephan; Orth, Peter P.

    2015-01-01

    Interacting cold-atomic gases in optical lattices offer an experimental approach to outstanding problems of many body physics. One important example is the interplay of interaction and topology which promises to generate a variety of exotic phases such as the fractionalized Chern insulator or the topological Mott insulator. Both theoretically understanding these states of matter and finding suitable systems that host them have proven to be challenging problems. Here we propose a cold-atom setup where Hubbard on-site interactions give rise to spin liquid-like phases: weak and strong topological Mott insulators. They represent the celebrated paradigm of an interacting and topological quantum state with fractionalized spinon excitations that inherit the topology of the non-interacting system. Our proposal shall help to pave the way for a controlled experimental investigation of this exotic state of matter in optical lattices. Furthermore, it allows for the investigation of a dimensional crossover from a two-dimensional quantum spin Hall insulating phase to a three-dimensional strong topological insulator by tuning the hopping between the layers. PMID:25669431

  10. Low dimensional Mott material: Transport in ultra thin epitaxial LaNiO3

    NASA Astrophysics Data System (ADS)

    Son, Junwoo; Moetakef, Pouya; Lebeau, James M.; Ouellette, Daniel; Balents, Leon; Allen, S. James; Stemmer, Susanne

    2010-03-01

    Ultrathin Mott materials, close to a metal-insulator transition, are expected to be sensitive to local bonding, coordination, strain and dimensionality. LaNiO3 films have recently attracted interest because of theoretical predictions of antiferromagnetism and high-temperature superconductivity in superlattices. We have grown ultrathin, epitaxial LaNiO3 on different substrates, (LaAlO3)0.3(Sr2AlTaO6)0.7 (LSAT) and LaAlO3 (LAO). High oxygen pressures were required for stoichiometric films. Atomic resolution Z-contrast imaging confirmed that all LaNiO3 films were epitaxial and continuous down to 2.5 nm. Resistivity, magnetoresistance, Hall coefficient and mobility were measured between 2 and 300 K. The resistivity (< 200 μφ cm) was comparable to bulk for films down to 5 nm on LSAT and 3 nm on LAO, indicating good oxygen stoichiometry. All films showed temperature dependent Hall coefficients indicative of both electron and hole contributions. For 4 nm films on LSAT and 2.5 nm films on LAO, weak localization was observed. Films below 4 nm on LSAT (tensile stress) were strongly localized while those on LAO (compressive stress) remained metallic at thicknesses down to 2.5 nm. We will discuss these results in the context of confinement in ultrathin Mott materials.

  11. Tuning a strain-induced orbital selective Mott transition in epitaxial VO2

    NASA Astrophysics Data System (ADS)

    Mukherjee, Shantanu; Quackenbush, N. F.; Paik, H.; Schlueter, C.; Lee, T.-L.; Schlom, D. G.; Piper, L. F. J.; Lee, Wei-Cheng

    2016-06-01

    We present evidence of strain-induced modulation of electron correlation effects and increased orbital anisotropy in the rutile phase of epitaxial VO2/TiO2 films from hard x-ray photoelectron spectroscopy and soft V L-edge x-ray absorption spectroscopy, respectively. By using the U(1) slave spin formalism, we further argue that the observed anisotropic correlation effects can be understood by a model of orbital selective Mott transition at a filling that is noninteger but close to the half filling. Because the overlaps of wave functions between d orbitals are modified by the strain, orbital-dependent renormalizations of the bandwidths and the onsite energy occur. These renormalizations generally result in different occupation numbers in different orbitals. We find that if the system has a noninteger filling number near the half filling such as for VO2, certain orbitals could reach an occupation number closer to half filling under the strain, resulting in a strong reduction in the quasiparticle weight Zα of that orbital. Our work demonstrates that such an orbital selective Mott transition, defined as the case with Zα=0 in some but not all orbitals, could be accessed by epitaxial-strain engineering of correlated electron systems.

  12. Topological edge Mott insulating state in two dimensions at finite temperatures: Bulk and edge analysis

    NASA Astrophysics Data System (ADS)

    Yoshida, Tsuneya; Kawakami, Norio

    2016-08-01

    We study a bilayer Kane-Mele-Hubbard model with lattice distortion and interlayer spin exchange interaction under cylinder geometry. Our analysis based on real-space dynamical mean field theory with continuous-time quantum Monte Carlo demonstrates the emergence of a topological edge Mott insulating (TEMI) state which hosts gapless edge modes only in collective spin excitations. This is confirmed by the numerical calculations at finite temperatures for the spin-Hall conductivity and the single-particle excitation spectrum; the spin-Hall conductivity is almost quantized, σspinx y˜2 (e /2 π ) , predicting gapless edge modes carrying the spin current, while the helical edge modes in the single-particle spectrum are gapped out with respecting symmetry. It is clarified how the TEMI state evolves from the ordinary spin-Hall insulating state with increasing the Hubbard interaction at a given temperature and then undergoes a phase transition to a trivial Mott insulating state. With a bosonization approach at zero temperature, we further address which collective modes host gapless edge modes in the TEMI state.

  13. Topological mott insulator in three-dimensional systems with quadratic band touching.

    PubMed

    Herbut, Igor F; Janssen, Lukas

    2014-09-01

    We argue that a three-dimensional electronic system with the Fermi level at the quadratic band touching point such as HgTe could be unstable with respect to the spontaneous formation of the (topological) Mott insulator at arbitrary weak long-range Coulomb interaction. The mechanism of the instability can be understood as the collision of Abrikosov's non-Fermi liquid fixed point with another, quantum critical, fixed point, which approaches it in the coupling space as the system's dimensionality d→dlow+, with the "lower critical dimension" 2Mott transition finally takes place at the critical temperature Tc∼T*exp[-zC/(dlow-d)1/2]. We estimate C=π/1.1, dynamical critical exponent z≈1.8, and the temperature scale kBT*≈(4m/melϵ^2)13.6  eV, with m as the band mass and ϵ as the dielectric constant.

  14. Anderson-Mott transition in arrays of a few dopant atoms in a silicon transistor.

    PubMed

    Prati, Enrico; Hori, Masahiro; Guagliardo, Filippo; Ferrari, Giorgio; Shinada, Takahiro

    2012-07-01

    Dopant atoms are used to control the properties of semiconductors in most electronic devices. Recent advances such as single-ion implantation have allowed the precise positioning of single dopants in semiconductors as well as the fabrication of single-atom transistors, representing steps forward in the realization of quantum circuits. However, the interactions between dopant atoms have only been studied in systems containing large numbers of dopants, so it has not been possible to explore fundamental phenomena such as the Anderson-Mott transition between conduction by sequential tunnelling through isolated dopant atoms, and conduction through thermally activated impurity Hubbard bands. Here, we observe the Anderson-Mott transition at low temperatures in silicon transistors containing arrays of two, four or six arsenic dopant atoms that have been deterministically implanted along the channel of the device. The transition is induced by controlling the spacing between dopant atoms. Furthermore, at the critical density between tunnelling and band transport regimes, we are able to change the phase of the electron system from a frozen Wigner-like phase to a Fermi glass by increasing the temperature. Our results open up new approaches for the investigation of coherent transport, band engineering and strongly correlated systems in condensed-matter physics.

  15. Doping-driven orbital-selective Mott transition in multi-band Hubbard models with crystal field splitting

    NASA Astrophysics Data System (ADS)

    Yilin, Wang; Li, Huang; Liang, Du; Xi, Dai

    2016-03-01

    We have studied the doping-driven orbital-selective Mott transition in multi-band Hubbard models with equal band width in the presence of crystal field splitting. Crystal field splitting lifts one of the bands while leaving the others degenerate. We use single-site dynamical mean-field theory combined with continuous time quantum Monte Carlo impurity solver to calculate a phase diagram as a function of total electron filling N and crystal field splitting Δ. We find a large region of orbital-selective Mott phase in the phase diagram when the doping is large enough. Further analysis indicates that the large region of orbital-selective Mott phase is driven and stabilized by doping. Such models may account for the orbital-selective Mott transition in some doped realistic strongly correlated materials. Project supported by the National Natural Science Foundation of China (Grant No. 2011CBA00108) and the National Basic Research Program of China (Grant No. 2013CB921700).

  16. Angle Resolved Photoemission Study of a Mott Insulator and Its Evolution to a High Temperature Superconductor

    NASA Astrophysics Data System (ADS)

    Ronning, F.

    2002-03-01

    One of the most remarkable facts about the high temperature superconductors is their close proximity to an antiferromagnetically ordered Mott insulating phase. This fact suggests that to understand superconductivity in the cuprates we must first understand the insulating regime. Due to material properties the technique of angle resolved photoemission is ideally suited to study the electronic structure in the cuprates. Thus, a natural starting place to unlocking the secrets of high Tc would appears to be with a photoemission investigation of insulating cuprates. This dissertation presents the results of precisely such a study. In particular, we have focused on the compound Ca2-xNaxCuO2Cl2. With increasing Na content this system goes from an antiferromagnetic Mott insulator with a Neel transition of 256K to a superconductor with an optimal transition temperature of 28K. At half filling we have found an asymmetry in the integrated spectral weight, which can be related to the occupation probability, n(k). This has led us to identify a d-wave-like dispersion in the insulator, which in turn implies that the high energy pseudogap as seen by photoemission is a remnant property of the insulator. These results are robust features of the insulator which we found in many different compounds and experimental conditions. By adding Na we were able to study the evolution of the electronic structure across the insulator to metal transition. We found that the chemical potential shifts as holes are doped into the system. This picture is in sharp contrast to the case of La2-xSrxCuO4 where the chemical potential remains fixed and states are created inside the gap. Furthermore, the low energy excitations (ie the Fermi surface) in metallic Ca1.9Na0.1CuO2Cl2 is most well described as a Fermi arc, although the high binding energy features reveal the presence of shadow bands. Thus, the results in this dissertation provide a new avenue for understanding the evolution of the Mott insulator to

  17. Quantum melting of magnetic order in an organic dimer Mott-insulating system

    NASA Astrophysics Data System (ADS)

    Naka, Makoto; Ishihara, Sumio

    2016-05-01

    Quantum entanglement effects between the electronic spin and charge degrees of freedom are examined in an organic molecular solid, termed a dimer Mott-insulating system, in which molecular dimers are arranged in a crystal as fundamental units. A low energy effective model includes an antisymmetric exchange interaction, as one of the dominant magnetic interactions. This interaction favors a 90 deg spin configuration, and competes with the Heisenberg-type exchange interaction. Stabilities of the magnetic ordered phases are examined by using the spin-wave theory, as well as the Schwinger-boson theory. It is found that the spin-charge interaction promotes an instability of the long-range magnetic ordered state around a parameter region where two spin-spiral phases are merged. Implication for the quantum spin liquid state observed in κ -(BEDT-TTF)2Cu2 (CN) 3 is discussed.

  18. Haldane-Hubbard Mott Insulator: From Tetrahedral Spin Crystal to Chiral Spin Liquid.

    PubMed

    Hickey, Ciarán; Cincio, Lukasz; Papić, Zlatko; Paramekanti, Arun

    2016-04-01

    Motivated by cold atom experiments on Chern insulators, we study the honeycomb lattice Haldane-Hubbard Mott insulator of spin-1/2 fermions using exact diagonalization and density matrix renormalization group methods. We show that this model exhibits various chiral magnetic orders including a wide regime of triple-Q tetrahedral order. Incorporating third-neighbor hopping frustrates and ultimately melts this tetrahedral spin crystal. From analyzing the low energy spectrum, many-body Chern numbers, entanglement spectra, and modular matrices, we identify the molten state as a chiral spin liquid (CSL) with gapped semion excitations. We formulate and study the Chern-Simons-Higgs field theory of the exotic CSL-to-tetrahedral spin crystallization transition.

  19. Excitonic magnetism in Van Vleck-type d4 Mott insulators.

    PubMed

    Khaliullin, Giniyat

    2013-11-01

    In Mott insulators with the t(2g)4 electronic configuration such as of Re3+, Ru4+, Os4+, and Ir5+ ions, spin-orbit coupling dictates a Van Vleck-type nonmagnetic ground state with an angular momentum J=0, and the magnetic response is governed by gapped singlet-triplet excitations. We derive the exchange interactions between these excitons and study their collective behavior on different lattices. In perovskites, a conventional Bose condensation of excitons into a magnetic state is found, while an unexpected one-dimensional behavior supporting spin-liquid states emerges in honeycomb lattices, due to the bond directional nature of exciton interactions in the case of 90° d-p-d bonding geometry.

  20. Haldane-Hubbard Mott Insulator: From Tetrahedral Spin Crystal to Chiral Spin Liquid

    NASA Astrophysics Data System (ADS)

    Hickey, Ciarán; Cincio, Lukasz; Papić, Zlatko; Paramekanti, Arun

    2016-04-01

    Motivated by cold atom experiments on Chern insulators, we study the honeycomb lattice Haldane-Hubbard Mott insulator of spin-1 /2 fermions using exact diagonalization and density matrix renormalization group methods. We show that this model exhibits various chiral magnetic orders including a wide regime of triple-Q tetrahedral order. Incorporating third-neighbor hopping frustrates and ultimately melts this tetrahedral spin crystal. From analyzing the low energy spectrum, many-body Chern numbers, entanglement spectra, and modular matrices, we identify the molten state as a chiral spin liquid (CSL) with gapped semion excitations. We formulate and study the Chern-Simons-Higgs field theory of the exotic CSL-to-tetrahedral spin crystallization transition.

  1. Mott Electrons in an Artificial Graphenelike Crystal of Rare-Earth Nickelate.

    PubMed

    Middey, S; Meyers, D; Doennig, D; Kareev, M; Liu, X; Cao, Y; Yang, Zhenzhong; Shi, Jinan; Gu, Lin; Ryan, P J; Pentcheva, R; Freeland, J W; Chakhalian, J

    2016-02-01

    Deterministic control over the periodic geometrical arrangement of the constituent atoms is the backbone of the material properties, which, along with the interactions, define the electronic and magnetic ground state. Following this notion, a bilayer of a prototypical rare-earth nickelate, NdNiO_{3}, combined with a dielectric spacer, LaAlO_{3}, has been layered along the pseudocubic [111] direction. The resulting artificial graphenelike Mott crystal with magnetic 3d electrons has antiferromagnetic correlations. In addition, a combination of resonant X-ray linear dichroism measurements and ab initio calculations reveal the presence of an ordered orbital pattern, which is unattainable in either bulk nickelates or nickelate based heterostructures grown along the [001] direction. These findings highlight another promising venue towards designing new quantum many-body states by virtue of geometrical engineering. PMID:26894726

  2. Using nonequilibrium dynamics to probe competing orders in a Mott-Peierls system

    DOE PAGESBeta

    Wang, Y.; Moritz, B.; Chen, C. -C.; Jia, C. J.; van Veenendaal, M.; Devereaux, T. P.

    2016-02-24

    Competition between ordered phases, and their associated phase transitions, are significant in the study of strongly correlated systems. Here, we examine one aspect, the nonequilibrium dynamics of a photoexcited Mott-Peierls system, using an effective Peierls-Hubbard model and exact diagonalization. Near a transition where spin and charge become strongly intertwined, we observe antiphase dynamics and a coupling-strength-dependent suppression or enhancement in the static structure factors. The renormalized bosonic excitations coupled to a particular photoexcited electron can be extracted, which provides an approach for characterizing the underlying bosonic modes. The results from this analysis for different electronic momenta show an uneven softeningmore » due to a stronger coupling near kF. As a result, this behavior reflects the strong link between the fermionic momenta, the coupling vertices, and ultimately, the bosonic susceptibilities when multiple phases compete for the ground state of the system.« less

  3. Hydrogen-like Wannier-Mott Excitons in Single Crystal of Methylammonium Lead Bromide Perovskite.

    PubMed

    Tilchin, Jenya; Dirin, Dmitry N; Maikov, Georgy I; Sashchiuk, Aldona; Kovalenko, Maksym V; Lifshitz, Efrat

    2016-06-28

    A thorough investigation of exciton properties in bulk CH3NH3PbBr3 perovskite single crystals was carried out by recording the reflectance, steady-state and transient photoluminescence spectra of submicron volumes across the crystal. The study included an examination of the spectra profiles at various temperatures and laser excitation fluencies. The results resolved the first and second hydrogen-like Wannier-Mott exciton transitions at low temperatures, from which the ground-state exciton's binding energy of 15.33 meV and Bohr radius of ∼4.38 nm were derived. Furthermore, the photoluminescence temperature dependence suggested dominance of delayed exciton emission at elevated temperatures, originating from detrapping of carriers from shallow traps or/and from retrapping of electron-hole pairs into exciton states. The study revealed knowledge about several currently controversial issues that have an impact on functionality of perovskite materials in optoelectronic devices. PMID:27249335

  4. External pumping of hybrid nanostructures in microcavity with Frenkel and Wannier-Mott excitons

    NASA Astrophysics Data System (ADS)

    Dubovskiy, O. A.; Agranovich, V. M.

    2016-09-01

    The exciton-exciton interaction in hybrid nanostructures with resonating Frenkel and Wannier-Mott excitons was investigated in many publications. In microcavity the hybrid nanostructures can be exposed to different types of optical pumping, the most common one being pumping through one of the microcavity side. However, not investigated and thus never been discussed the hybrid excitons generation by pumping of confined quantum wells from the side of empty microcavity without nanostructures in a wave guided configuration. Here, we consider the hybrid excitations in cavity with organic and inorganic quantum wells and with different types of pumping from external source. The frequency dependence for intensity of excitations in hybrid structure is also investigated. The results may be used for search of most effective fluorescence and relaxation processes. The same approach may be used when both quantum wells are organic or inorganic.

  5. Observing quantum trajectories: From Mott's problem to quantum Zeno effect and back

    NASA Astrophysics Data System (ADS)

    de Gosson, Maurice; Hiley, Basil; Cohen, Eliahu

    2016-11-01

    The experimental results of Kocsis et al., Mahler et al. and the proposed experiments of Morley et al. show that it is possible to construct "trajectories" in interference regions in a two-slit interferometer. These results call for a theoretical re-appraisal of the notion of a "quantum trajectory" first introduced by Dirac and in the present paper we re-examine this notion from the Bohm perspective based on Hamiltonian flows. In particular, we examine the short-time propagator and the role that the quantum potential plays in determining the form of these trajectories. These trajectories differ from those produced in a typical particle tracker and the key to this difference lies in the active suppression of the quantum potential necessary to produce Mott-type trajectories. We show, using a rigorous mathematical argument, how the active suppression of this potential arises. Finally we discuss in detail how this suppression also accounts for the quantum Zeno effect.

  6. Mott glass to superfluid transition for random bosons in two dimensions

    NASA Astrophysics Data System (ADS)

    Iyer, S.; Pekker, D.; Refael, G.

    2012-03-01

    We study the zero-temperature superfluid-insulator transition for a two-dimensional model of interacting, lattice bosons in the presence of quenched disorder and particle-hole symmetry. We follow the approach of a recent series of papers by Altman, Kafri, Polkovnikov, and Refael, in which the strong disorder renormalization group is used to study disordered bosons in one dimension. Adapting this method to two dimensions, we study several different species of disorder and uncover universal features of the superfluid-insulator transition. In particular, we locate an unstable finite disorder fixed point that governs the transition between the superfluid and a gapless, glassy insulator. We present numerical evidence that this glassy phase is the incompressible Mott glass and that the transition from this phase to the superfluid is driven by a percolation-type process. Finally, we provide estimates of the critical exponents governing this transition.

  7. A Mott Glass to Superfluid Transition for Random Bosons in Two Dimensions

    NASA Astrophysics Data System (ADS)

    Pekker, David; Iyer, Shankar; Refael, Gil

    2012-02-01

    We study the zero temperature superfluid-insulator transition for a two-dimensional model of interacting, lattice bosons in the presence of quenched disorder and particle-hole symmetry. We follow the approach of a recent series of papers by Altman, Kafri, Polkovnikov, and Refael, in which the strong disorder renormalization group is used to study disordered bosons in one dimension. Adapting this method to two dimensions, we study several different species of disorder and uncover universal features of the superfluid-insulator transition. In particular, we locate an unstable finite disorder fixed point that governs the transition between the superfluid and a gapless, glassy insulator. We present numerical evidence that this glassy phase is the incompressible Mott glass and that the transition from this phase to the superfluid is driven by percolation-type process. Finally, we provide estimates of the critical exponents governing this transition.

  8. Frenkel-like Wannier-Mott excitons in few-layer Pb I2

    NASA Astrophysics Data System (ADS)

    Toulouse, Alexis S.; Isaacoff, Benjamin P.; Shi, Guangsha; Matuchová, Marie; Kioupakis, Emmanouil; Merlin, Roberto

    2015-04-01

    Optical measurements and first-principles calculations of the band structure and exciton states in direct-gap bulk and few-layer Pb I2 indicate that the n =1 exciton is Frenkel-like in nature in that its energy exhibits a weak dependence on thickness down to atomic-length scales. Results reveal large increases in the gap and exciton binding energy with a decreasing number of layers and a transition of the fundamental gap, which becomes indirect for one and two monolayers. Calculated values are in reasonable agreement with a particle-in-a-box model relying on the Wannier-Mott theory of exciton formation. General arguments and existing data suggest that the Frenkel-like character of the lowest exciton is a universal feature of wide-gap layered semiconductors whose effective masses and dielectric constants give bulk Bohr radii that are on the order of the layer spacing.

  9. Mott metal-insulator transition in a metallic liquid - Gutzwiller molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Barros, Kipton; Chern, Gia-Wei; Batista, Cristian D.; Kress, Joel D.; Kotliar, Gabriel

    2015-03-01

    Molecular dynamics (MD) simulations are crucial to modern computational physics, chemistry, and materials science, especially when combined with potentials derived from density-functional theory. However, even in state of the art MD codes, the on-site Coulomb repulsion is only treated at the self-consistent Hartree-Fock level. This standard approximation may miss important effects due to electron correlations. The Gutzwiller variational method captures essential correlated-electron physics yet is much faster than, e.g., the dynamical-mean field theory approach. We present our efficient Gutzwiller-MD implementation. With it, we investigate the Mott metal-insulator transition in a metallic fluid and uncover several surprising static and dynamic properties of this system.

  10. Phase coexistence and Mott metal-insulator transition in the doped Hubbard-Holstein model

    NASA Astrophysics Data System (ADS)

    Moradi Kurdestany, Jamshid; Satpathy, Sashi

    2015-03-01

    Motivated by recent progress in the understanding of the Mott insulators away from half filling [?], often observed in the oxide materials, we study the role of the electron-lattice interaction vis-à-vis the electron correlations by studying the one-band Hubbard-Holstein model using the Gutzwiller variational method. Our theory predicts phase separation for sufficiently strong electron-lattice interaction, which however is frustrated in the solid due to the long-range Coulomb interaction of the dopant atoms, resulting in puddles of metallic phases embedded in the insulating matrix. Metallic state occurs when the volume fraction of the metallic phase exceeds the percolation threshold, as the dopant concentration is increased. Connection is made with the experimentally observed metal-insulator transition in the complex oxides.

  11. Spin-orbit coupling and electronic charge effects in Mott insulators

    DOE PAGESBeta

    Zhu, Shan; Li, You -Quan; Batista, Cristian D.

    2014-11-04

    We derive the effective charge- and current-density operators for the strong-coupling limit of a single-band Mott insulator in the presence of spin-orbit coupling and show that the spin-orbit contribution to the effective charge density leads to novel mechanisms for multiferroic behavior. In some sense, these mechanisms are the electronic counterpart of the ionic-based mechanisms, which have been proposed for explaining the electric polarization induced by spiral spin orderings. In addition, the new electronic mechanisms are illustrated by considering cycloidal and proper-screw magnetic orderings on sawtooth and kagome lattices. As for the isotropic case, geometric frustration is crucial for achieving thismore » purely electronic coupling between spin and charge degrees of freedom.« less

  12. Surface Effects on the Mott-Hubbard Transition in Archetypal V{2}O{3}.

    PubMed

    Lantz, G; Hajlaoui, M; Papalazarou, E; Jacques, V L R; Mazzotti, A; Marsi, M; Lupi, S; Amati, M; Gregoratti, L; Si, L; Zhong, Z; Held, K

    2015-12-01

    We present an experimental and theoretical study exploring surface effects on the evolution of the metal-insulator transition in the model Mott-Hubbard compound Cr-doped V{2}O{3}. We find a microscopic domain formation that is clearly affected by the surface crystallographic orientation. Using scanning photoelectron microscopy and x-ray diffraction, we find that surface defects act as nucleation centers for the formation of domains at the temperature-induced isostructural transition and favor the formation of microscopic metallic regions. A density-functional theory plus dynamical mean-field theory study of different surface terminations shows that the surface reconstruction with excess vanadyl cations leads to doped, and hence more metallic, surface states, which explains our experimental observations. PMID:26684133

  13. Surface Effects on the Mott-Hubbard Transition in Archetypal V2O3

    NASA Astrophysics Data System (ADS)

    Lantz, G.; Hajlaoui, M.; Papalazarou, E.; Jacques, V. L. R.; Mazzotti, A.; Marsi, M.; Lupi, S.; Amati, M.; Gregoratti, L.; Si, L.; Zhong, Z.; Held, K.

    2015-12-01

    We present an experimental and theoretical study exploring surface effects on the evolution of the metal-insulator transition in the model Mott-Hubbard compound Cr-doped V2O3. We find a microscopic domain formation that is clearly affected by the surface crystallographic orientation. Using scanning photoelectron microscopy and x-ray diffraction, we find that surface defects act as nucleation centers for the formation of domains at the temperature-induced isostructural transition and favor the formation of microscopic metallic regions. A density-functional theory plus dynamical mean-field theory study of different surface terminations shows that the surface reconstruction with excess vanadyl cations leads to doped, and hence more metallic, surface states, which explains our experimental observations.

  14. Prospect of quantum anomalous Hall and quantum spin Hall effect in doped kagome lattice Mott insulators.

    PubMed

    Guterding, Daniel; Jeschke, Harald O; Valentí, Roser

    2016-01-01

    Electronic states with non-trivial topology host a number of novel phenomena with potential for revolutionizing information technology. The quantum anomalous Hall effect provides spin-polarized dissipation-free transport of electrons, while the quantum spin Hall effect in combination with superconductivity has been proposed as the basis for realizing decoherence-free quantum computing. We introduce a new strategy for realizing these effects, namely by hole and electron doping kagome lattice Mott insulators through, for instance, chemical substitution. As an example, we apply this new approach to the natural mineral herbertsmithite. We prove the feasibility of the proposed modifications by performing ab-initio density functional theory calculations and demonstrate the occurrence of the predicted effects using realistic models. Our results herald a new family of quantum anomalous Hall and quantum spin Hall insulators at affordable energy/temperature scales based on kagome lattices of transition metal ions. PMID:27185665

  15. Photoinduced phase transitions in narrow-gap Mott insulators: The case of VO2

    NASA Astrophysics Data System (ADS)

    He, Zhuoran; Millis, Andrew J.

    2016-03-01

    We study the nonequilibrium dynamics of photoexcited electrons in the narrow-gap Mott insulator VO2. The initial stages of relaxation are treated using a quantum Boltzmann equation methodology, which reveals a rapid (˜femtosecond time scale) relaxation to a pseudothermal state characterized by a few parameters that vary slowly in time. The long-time limit is then studied by a Hartree-Fock methodology, which reveals the possibility of nonequilibrium excitation to a new metastable M1 metal phase that is qualitatively consistent with a recent experiment. The general physical picture of photoexcitation driving a correlated electron system to a new state that is not accessible in equilibrium may be applicable in similar materials.

  16. Low energy Mott polarimetry of electrons from negative electron affinity photocathodes

    SciTech Connect

    Ciccacci, F.; De Rossi, S.; Campbell, D.M.

    1995-08-01

    We present data on the spin polarization {ital P} and quantum yield {ital Y} of electrons photoemitted from negative electron affinity semiconductors, including GaAs(100), GaAsP(100) alloy, and strained GaAs layer epitaxially grown on a GaAsP(100) buffer. Near photothreshold the following values for {ital P}({ital Y}) are, respectively, obtained: 26% (2.5{times}10{sup {minus}2}), 40% (1{times}10{sup {minus}3}), and 60% (1.5{times}10{sup {minus}4}). We describe in detail the apparatus used containing a low energy (10--25 keV) Mott polarimeter. The system, completely fitted in a small volume ({similar_to}10{sup 4} cm{sup 3}) ultrahigh vacuum chamber, is intended as a test facility for characterizing candidate photocathode materials for spin polarized electron sources. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  17. Spin-orbit coupling and electronic charge effects in Mott insulators

    SciTech Connect

    Zhu, Shan; Li, You -Quan; Batista, Cristian D.

    2014-11-04

    We derive the effective charge- and current-density operators for the strong-coupling limit of a single-band Mott insulator in the presence of spin-orbit coupling and show that the spin-orbit contribution to the effective charge density leads to novel mechanisms for multiferroic behavior. In some sense, these mechanisms are the electronic counterpart of the ionic-based mechanisms, which have been proposed for explaining the electric polarization induced by spiral spin orderings. In addition, the new electronic mechanisms are illustrated by considering cycloidal and proper-screw magnetic orderings on sawtooth and kagome lattices. As for the isotropic case, geometric frustration is crucial for achieving this purely electronic coupling between spin and charge degrees of freedom.

  18. Prospect of quantum anomalous Hall and quantum spin Hall effect in doped kagome lattice Mott insulators

    NASA Astrophysics Data System (ADS)

    Guterding, Daniel; Jeschke, Harald O.; Valentí, Roser

    2016-05-01

    Electronic states with non-trivial topology host a number of novel phenomena with potential for revolutionizing information technology. The quantum anomalous Hall effect provides spin-polarized dissipation-free transport of electrons, while the quantum spin Hall effect in combination with superconductivity has been proposed as the basis for realizing decoherence-free quantum computing. We introduce a new strategy for realizing these effects, namely by hole and electron doping kagome lattice Mott insulators through, for instance, chemical substitution. As an example, we apply this new approach to the natural mineral herbertsmithite. We prove the feasibility of the proposed modifications by performing ab-initio density functional theory calculations and demonstrate the occurrence of the predicted effects using realistic models. Our results herald a new family of quantum anomalous Hall and quantum spin Hall insulators at affordable energy/temperature scales based on kagome lattices of transition metal ions.

  19. Coexistence of Mott and superfluid domains of bosons confined in optical lattice

    NASA Astrophysics Data System (ADS)

    Khanore, Mukesh; Dey, Bishwajyoti

    2015-06-01

    We investigate ground state properties of the attractive Bose-gas confined on square optical lattice and superimposed wine-bottle-bottom or Mexican hat trap potential. The system is modeled by two-dimensional Bose-Hubbard model with attractive interactions and inhomogeneous lattice potential. We calculate the energy spectrum, the on-site number fluctuation, local density and local compressibility using numerical exact diagonalization method for incommensurate lattice filling. The trap potential has several degenerate minimum sites distributed along a ring at the wine-bottle-bottom. It is shown that beyond a certain value of the attractive interaction strength there is phase coherent condensate on these degenerate sites with finite value of the on-site number fluctuation and local compressibility giving rise to localized superfluidity or superfluidity on a ring. For the same value of the interaction strength the non-degenerate sites produces Mott region.

  20. Chiral Spin Liquids in Triangular-Lattice SU (N ) Fermionic Mott Insulators with Artificial Gauge Fields

    NASA Astrophysics Data System (ADS)

    Nataf, Pierre; Lajkó, Miklós; Wietek, Alexander; Penc, Karlo; Mila, Frédéric; Läuchli, Andreas M.

    2016-10-01

    We show that, in the presence of a π /2 artificial gauge field per plaquette, Mott insulating phases of ultracold fermions with SU (N ) symmetry and one particle per site generically possess an extended chiral phase with intrinsic topological order characterized by an approximate ground space of N low-lying singlets for periodic boundary conditions, and by chiral edge states described by the SU(N ) 1 Wess-Zumino-Novikov-Witten conformal field theory for open boundary conditions. This has been achieved by extensive exact diagonalizations for N between 3 and 9, and by a parton construction based on a set of N Gutzwiller projected fermionic wave functions with flux π /N per triangular plaquette. Experimental implications are briefly discussed.

  1. Low-temperature fabrication of VO2 thin film on ITO glass with a Mott transition

    NASA Astrophysics Data System (ADS)

    Lin, Tiegui; Wang, Langping; Wang, Xiaofeng; Zhang, Yufen

    2016-09-01

    Polycrystalline Vanadium dioxide (VO2) thin film can be fabricated on glass substrates by high power impulse magnetron sputtering at a relative high temperature. In order to apply an effective bias voltage on substrate and control the energy of the ions impinged to the substrate, conductive indium-tin oxide (ITO) glass was used as the substrate. UV-visible-near IR transmittance spectra and X-ray diffraction (XRD) patterns of the as-deposited films exhibited that M-VO2 thin film with a metal-insulator transition temperature of 37∘C was fabricated successfully at 300∘C with a bias voltage of ‑200V, and the calculated average crystalline size of this film was about 12nm. XRD patterns at varied temperatures showed that the structural change of MIT of the VO2 thin film was suppressed during the phase transition process, and a pure Mott transition was obtained.

  2. One-step approach to ARPES from strongly correlated solids: A Mott-Hubbard system

    NASA Astrophysics Data System (ADS)

    Kuzian, R. O.; Krasovskii, E. E.

    2016-09-01

    An expression is derived for angle-resolved photocurrent from a semi-infinite correlated system. Within the sudden approximation, the photocurrent is proportional to the spectral function of a one-particle two-time retarded Green's function G of an operator that creates an electron in a special quantum state χ localized at the surface. For a system described by a many-body single-band model, we present an analytical expression that relates the Green's function G with the Green's function of an infinite crystal Gb ,k(ω ) in Wannier representation. The role of final states and of the crystal surface is analyzed for a model Green's function of the infinite crystal with a three-peak spectral function typical of a Mott-Hubbard metal. The momentum dependences of both the quasiparticle pole position and the spectral weight of the incoherent band manifest themselves in the shape of the photocurrent energy distribution curve.

  3. JeffDescription of the Honeycomb Mott Insulatorα‑RuCl3

    NASA Astrophysics Data System (ADS)

    Koitzsch, A.; Habenicht, C.; Müller, E.; Knupfer, M.; Büchner, B.; Kandpal, H. C.; van den Brink, J.; Nowak, D.; Isaeva, A.; Doert, Th.

    2016-09-01

    Novel ground states might be realized in honeycomb lattices with strong spin-orbit coupling. Here we study the electronic structure of {\\alpha}-RuCl_3, in which the Ru ions are in a d5 configuration and form a honeycomb lattice, by angle-resolved photoemission, x-ray photoemission and electron energy loss spectroscopy supported by density functional theory and multiplet calculations. We find that {\\alpha}-RuCl_3 is a Mott insulator with significant spin-orbit coupling, whose low energy electronic structure is naturally mapped onto Jeff states. This makes {\\alpha}-RuCl_3 a promising candidate for the realization of Kitaev physics. Relevant electronic parameters such as the Hubbard energy U, the crystal field splitting 10Dq and the charge transfer energy are evaluated. Furthermore, we observe significant Cl photodesorption with time, which must be taken into account when interpreting photoemission and other surface sensitive experiments.

  4. 'A ticklish sort of affair': Charles Mott, Haydock Lodge and the economics of asylumdom.

    PubMed

    Hirst, David

    2005-09-01

    In June 1846 complaints about the treatment of a Welsh clergyman at the privately run Haydock Lodge Asylum in England heralded a series of allegations about maltreatment of pauper patients at the institution. These prompted a number of Parliamentary reports on the institution. Allegations were also made about connections between the asylum and officials at the Poor Law Commission. This article demonstrates that many of the problems at Haydock Lodge relate to the character and personal circumstances of its first Superintendent, Charles Mott, a former Assistant Poor Law Commissioner. Despite this specific causation, the Haydock Lodge affair had a more general influence in raising once again questions about the propriety of entrusting the care of publicly funded patients to private institutions.

  5. Sub-bandgap absorption in Ti implanted Si over the Mott limit

    NASA Astrophysics Data System (ADS)

    Olea, J.; del Prado, A.; Pastor, D.; Mártil, I.; González-Díaz, G.

    2011-06-01

    We have analyzed the structural and optical properties of Si implanted with very high Ti doses and subsequently pulsed-laser melted (PLM). After PLM, all samples exhibit an abrupt and roughly uniform, box-shaped Ti profile, with a concentration around 2 × 1020 cm-3, which is well above the Mott limit, within a 150 nm thick layer. Samples PLM-annealed at the highest energy density (1.8 J/cm2) exhibit good lattice reconstruction. Independent of the annealing energy density, in all of the samples we observe strong sub-bandgap absorption, with absorption coefficient values between 4 × 103 and 104 cm-1. These results are explained in terms of the formation of an intermediate band (IB) originated from the Ti deep levels.

  6. Hydrogen-like Wannier-Mott Excitons in Single Crystal of Methylammonium Lead Bromide Perovskite.

    PubMed

    Tilchin, Jenya; Dirin, Dmitry N; Maikov, Georgy I; Sashchiuk, Aldona; Kovalenko, Maksym V; Lifshitz, Efrat

    2016-06-28

    A thorough investigation of exciton properties in bulk CH3NH3PbBr3 perovskite single crystals was carried out by recording the reflectance, steady-state and transient photoluminescence spectra of submicron volumes across the crystal. The study included an examination of the spectra profiles at various temperatures and laser excitation fluencies. The results resolved the first and second hydrogen-like Wannier-Mott exciton transitions at low temperatures, from which the ground-state exciton's binding energy of 15.33 meV and Bohr radius of ∼4.38 nm were derived. Furthermore, the photoluminescence temperature dependence suggested dominance of delayed exciton emission at elevated temperatures, originating from detrapping of carriers from shallow traps or/and from retrapping of electron-hole pairs into exciton states. The study revealed knowledge about several currently controversial issues that have an impact on functionality of perovskite materials in optoelectronic devices.

  7. Haldane-Hubbard Mott Insulator: From Tetrahedral Spin Crystal to Chiral Spin Liquid.

    PubMed

    Hickey, Ciarán; Cincio, Lukasz; Papić, Zlatko; Paramekanti, Arun

    2016-04-01

    Motivated by cold atom experiments on Chern insulators, we study the honeycomb lattice Haldane-Hubbard Mott insulator of spin-1/2 fermions using exact diagonalization and density matrix renormalization group methods. We show that this model exhibits various chiral magnetic orders including a wide regime of triple-Q tetrahedral order. Incorporating third-neighbor hopping frustrates and ultimately melts this tetrahedral spin crystal. From analyzing the low energy spectrum, many-body Chern numbers, entanglement spectra, and modular matrices, we identify the molten state as a chiral spin liquid (CSL) with gapped semion excitations. We formulate and study the Chern-Simons-Higgs field theory of the exotic CSL-to-tetrahedral spin crystallization transition. PMID:27082001

  8. Prospect of quantum anomalous Hall and quantum spin Hall effect in doped kagome lattice Mott insulators

    PubMed Central

    Guterding, Daniel; Jeschke, Harald O.; Valentí, Roser

    2016-01-01

    Electronic states with non-trivial topology host a number of novel phenomena with potential for revolutionizing information technology. The quantum anomalous Hall effect provides spin-polarized dissipation-free transport of electrons, while the quantum spin Hall effect in combination with superconductivity has been proposed as the basis for realizing decoherence-free quantum computing. We introduce a new strategy for realizing these effects, namely by hole and electron doping kagome lattice Mott insulators through, for instance, chemical substitution. As an example, we apply this new approach to the natural mineral herbertsmithite. We prove the feasibility of the proposed modifications by performing ab-initio density functional theory calculations and demonstrate the occurrence of the predicted effects using realistic models. Our results herald a new family of quantum anomalous Hall and quantum spin Hall insulators at affordable energy/temperature scales based on kagome lattices of transition metal ions. PMID:27185665

  9. Prospect of quantum anomalous Hall and quantum spin Hall effect in doped kagome lattice Mott insulators.

    PubMed

    Guterding, Daniel; Jeschke, Harald O; Valentí, Roser

    2016-05-17

    Electronic states with non-trivial topology host a number of novel phenomena with potential for revolutionizing information technology. The quantum anomalous Hall effect provides spin-polarized dissipation-free transport of electrons, while the quantum spin Hall effect in combination with superconductivity has been proposed as the basis for realizing decoherence-free quantum computing. We introduce a new strategy for realizing these effects, namely by hole and electron doping kagome lattice Mott insulators through, for instance, chemical substitution. As an example, we apply this new approach to the natural mineral herbertsmithite. We prove the feasibility of the proposed modifications by performing ab-initio density functional theory calculations and demonstrate the occurrence of the predicted effects using realistic models. Our results herald a new family of quantum anomalous Hall and quantum spin Hall insulators at affordable energy/temperature scales based on kagome lattices of transition metal ions.

  10. Temperature and pressure dependent Mott potentials and their influence on self-limiting oxide film growth

    NASA Astrophysics Data System (ADS)

    Cai, Na; Zhou, Guangwen; Müller, Kathrin; Starr, David E.

    2012-10-01

    Classic Cabrera-Mott theory stipulates that the limited oxide-film growth results from electron tunneling from the metal through the oxide film to adsorbed oxygen. This leads to an electric field across the oxide film that assists ion migration for low-temperature oxide-film growth. Here, we show that the field-driven oxide-film growth can be manipulated via the temperature and pressure of oxidation. The magnitude of the self-generated electric field depends on the oxygen surface coverage that exhibits a Langmuir isotherm behavior with changes in temperature and oxygen pressure. These observations demonstrate the ability to tune an interfacial reaction via self-adaptation to its environment.

  11. The role of Mycobacteria Other Than Tuberculosis (MOTT) in patients with cystic fibrosis.

    PubMed

    Hjelt, K; Højlyng, N; Howitz, P; Illum, N; Munk, E; Valerius, N H; Fursted, K; Hansen, K N; Heltberg, I; Koch, C

    1994-01-01

    The purpose of this study was to estimate the frequency of and evaluate the clinical impact of pulmonary mycobacterial infections among cystic fibrosis (CF) patients. 185 CF patients aged 2.2-38.5 years were screened by sputum samples and by intracutaneous skin tests against tuberculin and sensitins produced from Mycobacterium chelonae subsp. abscessus, M. avium, M. intracellulare and M. scrofulaceum (the MAIS complex). The skin tests towards the sensitins in BCG-vaccinated patients (n = 60) were significantly influenced by the vaccination. 26 of the remaining 125 non-vaccinated patients had > or = 1 positive skin test (95% confidence limits 15-29%). The majority reacted against the MAIS complex. However, the reactions were similar to those of healthy siblings and an age-matched control group. Moreover, the lung function, growth and HbA1c were similar among skin test positive and negative patients. Three patients had repeated positive sputum cultures, the point prevalence being 1.6% (M. intracellulare, n = 2 and M. chelonae subsp. abscessus, n = 1). During the subsequent 4 years, 4 additional patients with M. chelonae subsp. abscessus were identified. Based on clinical observations, 5 of the infected patients were considered asymptomatic, while 2 might have been symptomatic. In 1 patient, M. chelonae subsp. abscessus disappeared spontaneously. Despite intensive treatment with new antibiotics against Mycobacteria Other Than Tuberculosis (MOTT) in 4 patients, the mycobacteria were not eradicated. In conclusion, MOTT infection was rare and the clinical impact difficult to prove. Treatment should focus on clinical improvement in the individual patient suspected of suffering from significant symptomatic infection. Eradication of the bacteria should not be expected. PMID:7855554

  12. Foundations of heavy-fermion superconductivity: lattice Kondo effect and Mott physics.

    PubMed

    Steglich, Frank; Wirth, Steffen

    2016-08-01

    This article overviews the development of heavy-fermion superconductivity, notably in such rare-earth-based intermetallic compounds which behave as Kondo-lattice systems. Heavy-fermion superconductivity is of unconventional nature in the sense that it is not mediated by electron-phonon coupling. Rather, in most cases the attractive interaction between charge carriers is apparently magnetic in origin. Fluctuations associated with an antiferromagnetic (AF) quantum critical point (QCP) play a major role. The first heavy-fermion superconductor CeCu2Si2 turned out to be the prototype of a larger group of materials for which the underlying, often pressure-induced, AF QCP is likely to be of a three-dimensional (3D) spin-density-wave (SDW) variety. For UBe13, the second heavy-fermion superconductor, a magnetic-field-induced 3D SDW QCP inside the superconducting phase can be conjectured. Such a 'conventional', itinerant QCP can be well understood within Landau's paradigm of order-parameter fluctuations. In contrast, the low-temperature normal-state properties of a few heavy-fermion superconductors are at odds with the Landau framework. They are characterized by an 'unconventional', local QCP which may be considered a zero-temperature 4 f-orbital selective Mott transition. Here, as concluded for YbRh2Si2, the breakdown of the Kondo effect concurring with the AF instability gives rise to an abrupt change of the Fermi surface. Very recently, superconductivity was discovered for this compound at ultra-low temperatures. Therefore, YbRh2Si2 along with CeRhIn5 under pressure provide a natural link between the large group of about fifty low-temperature heavy-fermion superconductors and other families of unconventional superconductors with substantially higher T c, e.g. the doped Mott insulators of the perovskite-type cuprates and the organic charge-transfer salts.

  13. Foundations of heavy-fermion superconductivity: lattice Kondo effect and Mott physics

    NASA Astrophysics Data System (ADS)

    Steglich, Frank; Wirth, Steffen

    2016-08-01

    This article overviews the development of heavy-fermion superconductivity, notably in such rare-earth-based intermetallic compounds which behave as Kondo-lattice systems. Heavy-fermion superconductivity is of unconventional nature in the sense that it is not mediated by electron-phonon coupling. Rather, in most cases the attractive interaction between charge carriers is apparently magnetic in origin. Fluctuations associated with an antiferromagnetic (AF) quantum critical point (QCP) play a major role. The first heavy-fermion superconductor CeCu2Si2 turned out to be the prototype of a larger group of materials for which the underlying, often pressure-induced, AF QCP is likely to be of a three-dimensional (3D) spin-density-wave (SDW) variety. For UBe13, the second heavy-fermion superconductor, a magnetic-field-induced 3D SDW QCP inside the superconducting phase can be conjectured. Such a ‘conventional’, itinerant QCP can be well understood within Landau’s paradigm of order-parameter fluctuations. In contrast, the low-temperature normal-state properties of a few heavy-fermion superconductors are at odds with the Landau framework. They are characterized by an ‘unconventional’, local QCP which may be considered a zero-temperature 4 f-orbital selective Mott transition. Here, as concluded for YbRh2Si2, the breakdown of the Kondo effect concurring with the AF instability gives rise to an abrupt change of the Fermi surface. Very recently, superconductivity was discovered for this compound at ultra-low temperatures. Therefore, YbRh2Si2 along with CeRhIn5 under pressure provide a natural link between the large group of about fifty low-temperature heavy-fermion superconductors and other families of unconventional superconductors with substantially higher T c, e.g. the doped Mott insulators of the perovskite-type cuprates and the organic charge-transfer salts.

  14. T-shaped GaAs quantum-wire lasers and the exciton Mott transition.

    PubMed

    Yoshita, M; Liu, S M; Okano, M; Hayamizu, Y; Akiyama, H; Pfeiffer, L N; West, K W

    2007-07-25

    T-shaped GaAs quantum-wire (T-wire) lasers fabricated by the cleaved-edge overgrowth method with molecular beam epitaxy on the interface improved by a growth-interrupt high-temperature anneal are measured to study the laser device physics and fundamental many-body physics in clean one-dimensional (1D) systems. A current-injection T-wire laser that has 20 periods of T-wires in the active region and a 0.5 mm long cavity with high-reflection coatings shows a low threshold current of 0.27 mA at 30 K. The origin of the laser gain above the lasing threshold is studied with the high-quality T-wire lasers by means of optical pumping. The lasing energy is about 5 meV below the photoluminescence (PL) peak of free excitons, and is on the electron-hole (e-h) plasma PL band at a high e-h carrier density. The observed energy shift excludes the laser gain due to free excitons, and it suggests a contribution from the e-h plasma instead. A systematic micro-PL study reveals that the PL evolves with the e-h density from a sharp exciton peak, via a biexciton peak, to an e-h-plasma PL band. The data demonstrate an important role of biexcitons in the exciton Mott transition. Comparison with microscopic theories points out some problems in the picture of the exciton Mott transition.

  15. Foundations of heavy-fermion superconductivity: lattice Kondo effect and Mott physics.

    PubMed

    Steglich, Frank; Wirth, Steffen

    2016-08-01

    This article overviews the development of heavy-fermion superconductivity, notably in such rare-earth-based intermetallic compounds which behave as Kondo-lattice systems. Heavy-fermion superconductivity is of unconventional nature in the sense that it is not mediated by electron-phonon coupling. Rather, in most cases the attractive interaction between charge carriers is apparently magnetic in origin. Fluctuations associated with an antiferromagnetic (AF) quantum critical point (QCP) play a major role. The first heavy-fermion superconductor CeCu2Si2 turned out to be the prototype of a larger group of materials for which the underlying, often pressure-induced, AF QCP is likely to be of a three-dimensional (3D) spin-density-wave (SDW) variety. For UBe13, the second heavy-fermion superconductor, a magnetic-field-induced 3D SDW QCP inside the superconducting phase can be conjectured. Such a 'conventional', itinerant QCP can be well understood within Landau's paradigm of order-parameter fluctuations. In contrast, the low-temperature normal-state properties of a few heavy-fermion superconductors are at odds with the Landau framework. They are characterized by an 'unconventional', local QCP which may be considered a zero-temperature 4 f-orbital selective Mott transition. Here, as concluded for YbRh2Si2, the breakdown of the Kondo effect concurring with the AF instability gives rise to an abrupt change of the Fermi surface. Very recently, superconductivity was discovered for this compound at ultra-low temperatures. Therefore, YbRh2Si2 along with CeRhIn5 under pressure provide a natural link between the large group of about fifty low-temperature heavy-fermion superconductors and other families of unconventional superconductors with substantially higher T c, e.g. the doped Mott insulators of the perovskite-type cuprates and the organic charge-transfer salts. PMID:27376190

  16. Anomalous scaling and breakdown of conventional density functional theory methods for the description of Mott phenomena and stretched bonds

    NASA Astrophysics Data System (ADS)

    Ying, Zu-Jian; Brosco, Valentina; Lopez, Giorgia Maria; Varsano, Daniele; Gori-Giorgi, Paola; Lorenzana, José

    2016-08-01

    Density functional theory provides the most widespread framework for the realistic description of the electronic structure of solids, but the description of strongly correlated systems has remained so far elusive. We consider a particular limit of electrons and ions in which a one-band description becomes exact all the way from the weakly correlated metallic regime to the strongly correlated Mott-Hubbard regime. We provide a necessary condition a density functional should fulfill to describe Mott-Hubbard behavior in this one-band limit and show that it is not satisfied by standard and widely used local, semilocal, and hybrid functionals. We illustrate the condition in the case of few-atom systems and provide an analytic approximation to the exact exchange-correlation potential based on a variational wave function which shows explicitly the correct behavior, combining in a neat way lattice and continuum methods.

  17. Ca2O3Fe2.6S2: an antiferromagnetic Mott insulator at proximity to bad metal

    NASA Astrophysics Data System (ADS)

    Zhang, Han; Wu, Xiaozhi; Li, Dandan; Jin, Shifeng; Chen, Xiao; Zhang, Tao; Lin, Zhiping; Shen, Shijie; Yuan, Duanduan; Chen, Xiaolong

    2016-04-01

    We report here the first layered iron oxychalcogenide Ca2O3Fe2.6S2 that contains both planar [Ca2FeO2]2+ and [Fe2OS2]2- layers with the shortest Fe-Fe bond length. This compound is a narrow band gap (~0.073 eV) Mott insulator. The observed antiferromagnetic (AFM) transition at 77 K is due to the ordered Fe vacancies, which can be suppressed by partial substitution of Se for S. We show that the vacancy-free phase Ca2O3Fe3S2 may become a metal with moderate electron correlation comparable to the parent compound LaOFeAs of corresponding superconductors. Our results imply that iron oxychalcogenide can be converted from an AFM Mott insulator into a bad metal like iron pnictides through Fe-Fe bond length shrinking.

  18. Transport coefficients of graphene: Interplay of impurity scattering, Coulomb interaction, and optical phonons

    NASA Astrophysics Data System (ADS)

    Xie, Hong-Yi; Foster, Matthew S.

    2016-05-01

    We study the electric and thermal transport of the Dirac carriers in monolayer graphene using the Boltzmann-equation approach. Motivated by recent thermopower measurements [F. Ghahari, H.-Y. Xie, T. Taniguchi, K. Watanabe, M. S. Foster, and P. Kim, Phys. Rev. Lett. 116, 136802 (2016), 10.1103/PhysRevLett.116.136802], we consider the effects of quenched disorder, Coulomb interactions, and electron-optical-phonon scattering. Via an unbiased numerical solution to the Boltzmann equation we calculate the electrical conductivity, thermopower, and electronic component of the thermal conductivity, and discuss the validity of Mott's formula and of the Wiedemann-Franz law. An analytical solution for the disorder-only case shows that screened Coulomb impurity scattering, although elastic, violates the Wiedemann-Franz law even at low temperature. For the combination of carrier-carrier Coulomb and short-ranged impurity scattering, we observe the crossover from the interaction-limited (hydrodynamic) regime to the disorder-limited (Fermi-liquid) regime. In the former, the thermopower and the thermal conductivity follow the results anticipated by the relativistic hydrodynamic theory. On the other hand, we find that optical phonons become non-negligible at relatively low temperatures and that the induced electron thermopower violates Mott's formula. Combining all of these scattering mechanisms, we obtain the thermopower that quantitatively coincides with the experimental data.

  19. Superfluid-Mott transitions and vortices in the Jaynes-Cummings-Hubbard lattices with time-reversal-symmetry breaking

    NASA Astrophysics Data System (ADS)

    Hayward, A. L. C.; Martin, A. M.

    2016-02-01

    We investigate the ground-state behavior of Jaynes-Cummings-Hubbard lattices in the presence of a synthetic magnetic field, via a Gutzwiller ansatz. Specifically, we study the superfluid-Mott transition and the formation of vortex lattices in the superfluid regime. We find a suppression of the superfluid fraction due to the frustration induced by the incommensurate magnetic and spacial lattice lengths. We also predict the formation of triangular vortex lattices inside the superfluid regime.

  20. A metallic mosaic phase and the origin of Mott-insulating state in 1T-TaS2

    PubMed Central

    Ma, Liguo; Ye, Cun; Yu, Yijun; Lu, Xiu Fang; Niu, Xiaohai; Kim, Sejoong; Feng, Donglai; Tománek, David; Son, Young-Woo; Chen, Xian Hui; Zhang, Yuanbo

    2016-01-01

    Electron–electron and electron–phonon interactions are two major driving forces that stabilize various charge-ordered phases of matter. In layered compound 1T-TaS2, the intricate interplay between the two generates a Mott-insulating ground state with a peculiar charge-density-wave (CDW) order. The delicate balance also makes it possible to use external perturbations to create and manipulate novel phases in this material. Here, we study a mosaic CDW phase induced by voltage pulses, and find that the new phase exhibits electronic structures entirely different from that of the original Mott ground state. The mosaic phase consists of nanometre-sized domains characterized by well-defined phase shifts of the CDW order parameter in the topmost layer, and by altered stacking relative to the layers underneath. We discover that the nature of the new phase is dictated by the stacking order, and our results shed fresh light on the origin of the Mott phase in 1T-TaS2. PMID:26961788

  1. Mott transition in CaFe2O4 at around 50 GPa

    NASA Astrophysics Data System (ADS)

    Greenberg, Eran; Rozenberg, Gregory Kh.; Xu, Weiming; Pasternak, Moshe P.; McCammon, Catherine; Glazyrin, Konstantin; Dubrovinsky, Leonid S.

    2013-12-01

    Electrical transport and magnetic properties of CaFe2O4 have been studied at pressures up to 70 GPa using Fe57 Mössbauer spectroscopy (MS), Raman spectroscopy, and electrical resistance measurements. These studies have shown the onset of the Mott transition (MT) at a pressure of around 50 GPa, leading to the collapse of Fe3+ magnetic moments and to the insulator-metal (IM) transition. The observed onset of the MT corroborates with the recently reported isostructural transition accompanied by a 12% decrease in the Fe polyhedral volume. An analysis of the alterations of the electrical transport, magnetic, and structural properties with pressure increase and at the transition range suggests that the coinciding IM transition, magnetic moment, and volume collapse at around 50 GPa are caused by the closure of the Hubbard gap driven by the high-spin to low-spin (HS-LS) transition. At that, since MS did not reveal any evidence of a preceding LS state, it could be inferred that the HS-LS transition immediately leads to an IM transition and complete collapse of magnetism.

  2. Defects, Disorder, and Strong Electron Correlations in Orbital Degenerate, Doped Mott Insulators

    NASA Astrophysics Data System (ADS)

    Avella, Adolfo; Oleś, Andrzej M.; Horsch, Peter

    2015-11-01

    We elucidate the effects of defect disorder and e -e interaction on the spectral density of the defect states emerging in the Mott-Hubbard gap of doped transition-metal oxides, such as Y1 -xCaxVO3. A soft gap of kinetic origin develops in the defect band and survives defect disorder for e -e interaction strengths comparable to the defect potential and hopping integral values above a doping dependent threshold; otherwise only a pseudogap persists. These two regimes naturally emerge in the statistical distribution of gaps among different defect realizations, which turns out to be of Weibull type. Its shape parameter k determines the exponent of the power-law dependence of the density of states at the chemical potential (k -1 ) and hence distinguishes between the soft gap (k ≥2 ) and the pseudogap (k <2 ) regimes. Both k and the effective gap scale with the hopping integral and the e -e interaction in a wide doping range. The motion of doped holes is confined by the closest defect potential and the overall spin-orbital structure. Such a generic behavior leads to complex nonhydrogenlike defect states that tend to preserve the underlying C -type spin and G -type orbital order and can be detected and analyzed via scanning tunneling microscopy.

  3. Design of Chern and Mott insulators in buckled 3 d oxide honeycomb lattices

    NASA Astrophysics Data System (ADS)

    Doennig, David; Baidya, Santu; Pickett, Warren E.; Pentcheva, Rossitza

    2016-04-01

    Perovskite (La X O3 )2/(LaAlO3)4(111) superlattices with X spanning the entire 3 d transition-metal series combine the strongly correlated, multiorbital nature of electrons in transition-metal oxides with a honeycomb lattice as a key feature. Based on density functional theory calculations including strong interaction effects, we establish trends in the evolution of electronic states as a function of several control parameters: band filling, interaction strength, spin-orbit coupling (SOC), and lattice instabilities. Competition between local pseudocubic and global trigonal symmetry as well as the additional flexibility provided by the magnetic and spin degrees of freedom of 3 d ions lead to a broad array of distinctive broken-symmetry ground states not accessible for the (001)-growth direction, offering a platform to design two-dimensional electronic functionalities. Constraining the symmetry between the two triangular sublattices causes X =Mn , Co, and Ti to emerge as Chern insulators driven by SOC. For X =Mn we illustrate how interaction strength and lattice distortions can tune these systems between a Dirac semimetal, a Chern and a trivial Mott insulator.

  4. Quantum criticality in the 122 iron pnictide superconductors emerging from orbital-selective Mottness

    NASA Astrophysics Data System (ADS)

    Das, S. D.; Laad, M. S.; Craco, L.; Gillett, J.; Tripathi, V.; Sebastian, S. E.

    2015-10-01

    The twin issues of the nature of the "normal" state and competing order(s) in the iron arsenides are central to understanding their unconventional, high-Tc superconductivity. We use a combination of transport anisotropy measurements on detwinned Sr (Fe1-xCox) 2As2 single crystals and local density approximation plus dynamical mean field theory (LDA + DMFT) calculations to revisit these issues. The peculiar resistivity anisotropy and its evolution with x are naturally interpreted in terms of an underlying orbital-selective Mott transition (OSMT) that gaps out the dx z or dy z states. Further, we use a Landau-Ginzburg approach using LDA + DMFT input to rationalize a wide range of anomalies seen up to optimal doping, providing strong evidence for secondary electronic nematic order. These findings suggest that strong dynamical fluctuations linked to a marginal quantum-critical point associated with this OSMT and a secondary electronic nematic order constitute an intrinsically electronic pairing mechanism for superconductivity in Fe arsenides.

  5. Direct Probing of the Mott Crossover in the SU (N ) Fermi-Hubbard Model

    NASA Astrophysics Data System (ADS)

    Hofrichter, Christian; Riegger, Luis; Scazza, Francesco; Höfer, Moritz; Fernandes, Diogo Rio; Bloch, Immanuel; Fölling, Simon

    2016-04-01

    We report on a detailed experimental investigation of the equation of state (EoS) of the three-dimensional Fermi-Hubbard model (FHM) in its generalized SU (N ) -symmetric form, using a degenerate ytterbium gas in an optical lattice. In its more common spin-1 /2 form, the FHM is a central model of condensed-matter physics. The generalization to N >2 was first used to describe multi-orbital materials and is expected to exhibit novel many-body phases in a complex phase diagram. By realizing and locally probing the SU (N ) FHM with ultracold atoms, we obtain model-free access to thermodynamic quantities. The measurement of the EoS and the local compressibility allows us to characterize the crossover from a compressible metal to an incompressible Mott insulator. We reach specific entropies above Néel order but below that of uncorrelated spins. Having access to the EoS of such a system represents an important step towards probing predicted novel SU (N ) phases.

  6. Ambient organic molecular passivation of Si yields near-ideal, Schottky-Mott limited, junctions

    NASA Astrophysics Data System (ADS)

    Har-Lavan, Rotem; Yaffe, Omer; Joshi, Pranav; Kazaz, Roy; Cohen, Hagai; Cahen, David

    2012-03-01

    We report near-perfect transfer of the electrical properties of oxide-free Si surface, modified by a molecular monolayer, to the interface of a junction made with that modified Si surface. Such behavior is highly unusual for a covalent, narrow bandgap semiconductor, such as Si. Short, ambient atmosphere, room temperature treatment of oxide-free Si(100) in hydroquinone (HQ)/alkyl alcohol solutions, fully passivates the Si surface, while allowing controlled change of the resulting surface potential. The junctions formed, upon contacting such surfaces with Hg, a metal that does not chemically interact with Si, follow the Schottky-Mott model for metal-semiconductor junctions closer than ever for Si-based junctions. Two examples of such ideal behavior are demonstrated: a) Tuning the molecular surface dipole over 400 mV, with only negligible band bending, by changing the alkyl chain length. Because of the excellent passivation this yields junctions with Hg with barrier heights that follow the change in the Si effective electron affinity nearly ideally. b) HQ/ methanol passivation of Si is accompanied by a large surface dipole, which suffices, as interface dipole, to drive the Si into strong inversion as shown experimentally via its photovoltaic effect. With only ˜0.3 nm molecular interlayer between the metal and the Si, our results proves that it is passivation and prevention of metal-semiconductor interactions that allow ideal metal-semiconductor junction behavior, rather than an insulating transport barrier.

  7. Mott physics and collective modes: An atomic approximation of the four-particle irreducible functional

    NASA Astrophysics Data System (ADS)

    Ayral, Thomas; Parcollet, Olivier

    2016-08-01

    We discuss a generalization of the dynamical mean field theory (DMFT) for strongly correlated systems close to a Mott transition based on a systematic approximation of the fully irreducible four-point vertex. It is an atomic-limit approximation of a functional of the one- and two-particle Green functions, built with the second Legendre transform of the free energy with respect to the two-particle Green function. This functional is represented diagrammatically by four-particle irreducible (4PI) diagrams. Like the dynamical vertex approximation (D Γ A ), the fully irreducible vertex is computed from a quantum impurity model whose bath is self-consistently determined by solving the parquet equations. However, in contrast with D Γ A and DMFT, the interaction term of the impurity model is also self-consistently determined. The method interpolates between the parquet approximation at weak coupling and the atomic limit, where it is exact. It is applicable to systems with short-range and long-range interactions.

  8. Featureless and nonfractionalized Mott insulators on the honeycomb lattice at 1/2 site filling

    PubMed Central

    Kimchi, Itamar; Parameswaran, S. A.; Turner, Ari M.; Wang, Fa; Vishwanath, Ashvin

    2013-01-01

    Within the Landau paradigm, phases of matter are distinguished by spontaneous symmetry breaking. Implicit here is the assumption that a completely symmetric state exists: a paramagnet. At zero temperature such quantum featureless insulators may be forbidden, triggering either conventional order or topological order with fractionalized excitations. Such is the case for interacting particles when the particle number per unit cell, f, is not an integer. However, can lattice symmetries forbid featureless insulators even at integer f? An especially relevant case is the honeycomb (graphene) lattice—where free spinless fermions at (the two sites per unit cell mean is half-filling per site) are always metallic. Here we present wave functions for bosons, and a related spin-singlet wave function for spinful electrons, on the honeycomb lattice and demonstrate via quantum to classical mappings that they do form featureless Mott insulators. The construction generalizes to symmorphic lattices at integer f in any dimension. Our results explicitly demonstrate that in this case, despite the absence of a noninteracting insulator at the same filling, lack of order at zero temperature does not imply fractionalization.

  9. Superfluid-Mott insulator transition in spin-orbit coupled Bose-Hubbard Model

    NASA Astrophysics Data System (ADS)

    Iskin, Menderes; Bolukbasi, Ahmet T. B.

    2014-05-01

    We consider a square optical lattice in two dimensions and study the effects of both the strength and symmetry of spin-orbit coupling (SOC) and Zeeman field on the ground-state, i.e., Mott insulator (MI) and superfluid (SF), phases and phase diagram, i.e., MI-SF phase transition boundary, of the two-component Bose-Hubbard model. In particular, based on a variational Gutzwiller ansatz, our numerical calculations show that the spin-orbit coupled SF phase is a nonuniform (twisted) one with its phase (but not the magnitude) of the order parameter modulating from site to site. Fully analytical insights into the numerical results are also given. A. T. B is supported by TÜBİTAK 2218 Domestic Postdoctoral Fellowship Program, and M. I. is supported by the Marie Curie IRG Grant No. FP7-PEOPLE-IRG-2010-268239, TÜBİTAK Career Grant No. 3501-110T839, and TÜBA-GEBİP.

  10. Bose glass and Mott glass of quasiparticles in a doped quantum magnet.

    PubMed

    Yu, Rong; Yin, Liang; Sullivan, Neil S; Xia, J S; Huan, Chao; Paduan-Filho, Armando; Oliveira, Nei F; Haas, Stephan; Steppke, Alexander; Miclea, Corneliu F; Weickert, Franziska; Movshovich, Roman; Mun, Eun-Deok; Scott, Brian L; Zapf, Vivien S; Roscilde, Tommaso

    2012-09-20

    The low-temperature states of bosonic fluids exhibit fundamental quantum effects at the macroscopic scale: the best-known examples are Bose-Einstein condensation and superfluidity, which have been tested experimentally in a variety of different systems. When bosons interact, disorder can destroy condensation, leading to a 'Bose glass'. This phase has been very elusive in experiments owing to the absence of any broken symmetry and to the simultaneous absence of a finite energy gap in the spectrum. Here we report the observation of a Bose glass of field-induced magnetic quasiparticles in a doped quantum magnet (bromine-doped dichloro-tetrakis-thiourea-nickel, DTN). The physics of DTN in a magnetic field is equivalent to that of a lattice gas of bosons in the grand canonical ensemble; bromine doping introduces disorder into the hopping and interaction strength of the bosons, leading to their localization into a Bose glass down to zero field, where it becomes an incompressible Mott glass. The transition from the Bose glass (corresponding to a gapless spin liquid) to the Bose-Einstein condensate (corresponding to a magnetically ordered phase) is marked by a universal exponent that governs the scaling of the critical temperature with the applied field, in excellent agreement with theoretical predictions. Our study represents a quantitative experimental account of the universal features of disordered bosons in the grand canonical ensemble.

  11. Li2RhO3: A spin-glassy relativistic Mott insulator

    NASA Astrophysics Data System (ADS)

    Luo, Yongkang; Cao, Chao; Si, Bingqi; Li, Yuke; Bao, Jinke; Guo, Hanjie; Yang, Xiaojun; Shen, Chenyi; Feng, Chunmu; Dai, Jianhui; Cao, Guanghan; Xu, Zhu-an

    2013-04-01

    Motivated by the rich interplay among electronic correlation, spin-orbit coupling (SOC), crystal-field splitting, and geometric frustrations in the honeycomblike lattice, we systematically investigated the electronic and magnetic properties of Li2RhO3. The material is semiconducting with a narrow band gap of Δ˜78 meV, and its temperature dependence of resistivity conforms to a three-dimensional variable range hopping mechanism. No long-range magnetic ordering was found down to 0.5 K, due to the geometric frustrations. Instead, single atomic spin-glass behavior below the spin-freezing temperature (˜6 K) was observed and its spin dynamics obeys the universal critical slowing down scaling law. A first-principles calculation suggested it to be a relativistic Mott insulator mediated by both electronic correlation and SOC. With moderate strength of electronic correlation and SOC, our results shed light on the research of the Heisenberg-Kitaev model in realistic materials.

  12. Sitewise manipulations and Mott insulator-superfluid transition of interacting photons using superconducting circuit simulators

    DOE PAGESBeta

    Deng, Xiuhao; Jia, Chunjing; Chien, Chih-Chun

    2015-02-23

    We report that the Bose Hubbard model (BHM) of interacting bosons in a lattice has been a paradigm in many-body physics, and it exhibits a Mott insulator (MI)-superfluid (SF) transition at integer filling. Here a quantum simulator of the BHM using a superconducting circuit is proposed. Specifically, a superconducting transmission line resonator supporting microwave photons is coupled to a charge qubit to form one site of the BHM, and adjacent sites are connected by a tunable coupler. To obtain a mapping from the superconducting circuit to the BHM, we focus on the dispersive regime where the excitations remain photonlike. Standardmore » perturbation theory is implemented to locate the parameter range where the MI-SF transition may be simulated. This simulator allows single-site manipulations and we illustrate this feature by considering two scenarios where a single-site manipulation can drive a MI-SF transition. The transition can be analyzed by mean-field analyses, and the exact diagonalization was implemented to provide accurate results. The variance of the photon density and the fidelity metric clearly show signatures of the transition. Lastly, experimental realizations and other possible applications of this simulator are also discussed.« less

  13. Sitewise manipulations and Mott insulator-superfluid transition of interacting photons using superconducting circuit simulators

    SciTech Connect

    Deng, Xiuhao; Jia, Chunjing; Chien, Chih-Chun

    2015-02-23

    We report that the Bose Hubbard model (BHM) of interacting bosons in a lattice has been a paradigm in many-body physics, and it exhibits a Mott insulator (MI)-superfluid (SF) transition at integer filling. Here a quantum simulator of the BHM using a superconducting circuit is proposed. Specifically, a superconducting transmission line resonator supporting microwave photons is coupled to a charge qubit to form one site of the BHM, and adjacent sites are connected by a tunable coupler. To obtain a mapping from the superconducting circuit to the BHM, we focus on the dispersive regime where the excitations remain photonlike. Standard perturbation theory is implemented to locate the parameter range where the MI-SF transition may be simulated. This simulator allows single-site manipulations and we illustrate this feature by considering two scenarios where a single-site manipulation can drive a MI-SF transition. The transition can be analyzed by mean-field analyses, and the exact diagonalization was implemented to provide accurate results. The variance of the photon density and the fidelity metric clearly show signatures of the transition. Lastly, experimental realizations and other possible applications of this simulator are also discussed.

  14. Reliability of the one-crossing approximation in describing the Mott transition.

    PubMed

    Vildosola, V; Pourovskii, L V; Manuel, L O; Roura-Bas, P

    2015-12-01

    We assess the reliability of the one-crossing approximation (OCA) approach in a quantitative description of the Mott transition in the framework of the dynamical mean field theory (DMFT). The OCA approach has been applied in conjunction with DMFT to a number of heavy-fermion, actinide, transition metal compounds and nanoscale systems. However, several recent studies in the framework of impurity models pointed out serious deficiencies of OCA and raised questions regarding its reliability. Here we consider a single band Hubbard model on the Bethe lattice at finite temperatures and compare the results of OCA to those of a numerically exact quantum Monte Carlo (QMC) method. The temperature-local repulsion U phase diagram for the particle-hole symmetric case obtained by OCA is in good agreement with that of QMC, with the metal-insulator transition captured very well. We find, however, that the insulator to metal transition is shifted to higher values of U and, simultaneously, correlations in the metallic phase are significantly overestimated. This counter-intuitive behaviour is due to simultaneous underestimations of the Kondo scale in the metallic phase and the size of the insulating gap. We trace the underestimation of the insulating gap to that of the second moment of the high-frequency expansion of the impurity spectral density. Calculations of the system away from the particle-hole symmetric case are also presented and discussed. PMID:26565588

  15. On the possibility of many-body localization in a doped Mott insulator

    PubMed Central

    He, Rong-Qiang; Weng, Zheng-Yu

    2016-01-01

    Many-body localization (MBL) is currently a hot issue of interacting systems, in which quantum mechanics overcomes thermalization of statistical mechanics. Like Anderson localization of non-interacting electrons, disorders are usually crucial in engineering the quantum interference in MBL. For translation invariant systems, however, the breakdown of eigenstate thermalization hypothesis due to a pure many-body quantum effect is still unclear. Here we demonstrate a possible MBL phenomenon without disorder, which emerges in a lightly doped Hubbard model with very strong interaction. By means of density matrix renormalization group numerical calculation on a two-leg ladder, we show that whereas a single hole can induce a very heavy Nagaoka polaron, two or more holes will form bound pair/droplets which are all localized excitations with flat bands at low energy densities. Consequently, MBL eigenstates of finite energy density can be constructed as composed of these localized droplets spatially separated. We further identify the underlying mechanism for this MBL as due to a novel ‘Berry phase’ of the doped Mott insulator, and show that by turning off this Berry phase either by increasing the anisotropy of the model or by hand, an eigenstate transition from the MBL to a conventional quasiparticle phase can be realized. PMID:27752064

  16. Rydberg-Atom Quantum Simulation and Chern Number Characterization of a Topological Mott Insulator

    NASA Astrophysics Data System (ADS)

    Dauphin, Alexandre; Mueller, Markus; Martin-Delgado, Miguel-Angel

    2013-03-01

    In this talk we consider a system of spinless fermions with nearest and next-to-nearest neighbor repulsive Hubbard interactions on a honeycomb lattice within the mean-field treatment, and propose and analyze a realistic scheme for analog quantum simulation of this model with cold atoms in a two-dimensional hexagonal optical lattice. Besides a semi-metallic and a charge-density-wave ordered phase, the system exhibits a quantum anomalous Hall phase, which is generated dynamically, i.e. purely as a result of the repulsive fermionic interactions and in the absence of any external gauge fields. We establish the topological nature of this dynamically created Mott insulating phase by the numerical calculation of a Chern number, and study the possibility of coexistence of this phase with the other phases characterized by local order parameters. Based on the knowledge of the mean-field phase diagram, we then discuss in detail how the interacting Hamiltonian can be engineered effective ly by state-of-the-art experimental techniques for laser-dressing of cold fermionic ground-state atoms with electronically excited Rydberg states that exhibit strong dipolar interactions.

  17. Reliability of the one-crossing approximation in describing the Mott transition

    NASA Astrophysics Data System (ADS)

    Vildosola, V.; Pourovskii, L. V.; Manuel, L. O.; Roura-Bas, P.

    2015-12-01

    We assess the reliability of the one-crossing approximation (OCA) approach in a quantitative description of the Mott transition in the framework of the dynamical mean field theory (DMFT). The OCA approach has been applied in conjunction with DMFT to a number of heavy-fermion, actinide, transition metal compounds and nanoscale systems. However, several recent studies in the framework of impurity models pointed out serious deficiencies of OCA and raised questions regarding its reliability. Here we consider a single band Hubbard model on the Bethe lattice at finite temperatures and compare the results of OCA to those of a numerically exact quantum Monte Carlo (QMC) method. The temperature-local repulsion U phase diagram for the particle-hole symmetric case obtained by OCA is in good agreement with that of QMC, with the metal-insulator transition captured very well. We find, however, that the insulator to metal transition is shifted to higher values of U and, simultaneously, correlations in the metallic phase are significantly overestimated. This counter-intuitive behaviour is due to simultaneous underestimations of the Kondo scale in the metallic phase and the size of the insulating gap. We trace the underestimation of the insulating gap to that of the second moment of the high-frequency expansion of the impurity spectral density. Calculations of the system away from the particle-hole symmetric case are also presented and discussed.

  18. Modeling of oxidation of aluminum nanoparticles by using Cabrera Mott Model

    NASA Astrophysics Data System (ADS)

    Ramazanova, Zamart; Zyskin, Maxim; Martirosyan, Karen

    2012-10-01

    Our research focuses on modeling new Nanoenergetic Gas-Generator (NGG) formulations that rapidly release a large amount of gaseous products and generates shock and pressure waves. Nanoenergetic thermite reagents include mixtures of Al and metal oxides such as bismuth trioxide and iodine pentoxide. The research problem is considered a spherically symmetric case and used the Cabrera Mott oxidation model to describe the kinetics of oxide growth on spherical Al nanoparticles for evaluating reaction time which a process of the reaction with oxidizer happens on the outer part of oxide layer of aluminum ions are getting in contact with an oxidizing agent and react. We assumed that a ball of Al of radius 20 to 50 nm is covered by a thin oxide layer 2-4 nm and is surrounded by abundant amount of oxygen stored by oxidizers. The ball is rapidly heated up to ignition temperature to initiate self-sustaining oxidation reaction. As a result highly exothermic reaction is generated. In the oxide layer of excess concentrations of electrons and ions are dependent on the electric field potential with the corresponding of the Gibbs factors and that it conducts to the solution of a nonlinear Poisson equation for the electric field potential in a moving boundary domain. Motion of the boundary is determined by the gradient of a solution on the boundary. We investigated oxidation model numerically, using the COMSOL software utilizing finite element analysis. The computing results demonstrate that oxidation rate increases with the decreasing particle radius.

  19. Monte Carlo simulation of 1-10-keV electron scattering in an aluminum target

    NASA Astrophysics Data System (ADS)

    Kotera, Masatoshi; Murata, Kenji; Nagami, Koichi

    1981-12-01

    New Monte Carlo simulations of electron scattering based on the single scattering model have been performed in the low-energy region for an aluminum target, where two basic equations are required, namely the elastic scattering cross section and the energy-loss rate. We investigated the screened Rutherford equation and the Mott equation for two different atomic potentials for the former, and the Rao Sahib-Wittry equation (the modified Bethe equation) for the latter. The validity of each model is discussed in a comparison between Monte Carlo results and experimental results such as the electron range, electron backscattering, and electron transmission which have been reported by various authors. Consequently, it was found that a combination of the Mott cross section and the Rao Sahib-Wittry equation showed the best accuracy. However, the accuracy of a previous model with the screened Rutherford equation is not as bad as aniticipated because of the higher accuracy of the Born approximation for light elements such as Al, compared to Au.

  20. The 'Higgs' amplitude mode at the two-dimensional superfluid/Mott insulator transition.

    PubMed

    Endres, Manuel; Fukuhara, Takeshi; Pekker, David; Cheneau, Marc; Schauss, Peter; Gross, Christian; Demler, Eugene; Kuhr, Stefan; Bloch, Immanuel

    2012-07-25

    Spontaneous symmetry breaking plays a key role in our understanding of nature. In relativistic quantum field theory, a broken continuous symmetry leads to the emergence of two types of fundamental excitation: massless Nambu-Goldstone modes and a massive 'Higgs' amplitude mode. An excitation of Higgs type is of crucial importance in the standard model of elementary particle physics, and also appears as a fundamental collective mode in quantum many-body systems. Whether such a mode exists in low-dimensional systems as a resonance-like feature, or whether it becomes overdamped through coupling to Nambu-Goldstone modes, has been a subject of debate. Here we experimentally find and study a Higgs mode in a two-dimensional neutral superfluid close to a quantum phase transition to a Mott insulating phase. We unambiguously identify the mode by observing the expected reduction in frequency of the onset of spectral response when approaching the transition point. In this regime, our system is described by an effective relativistic field theory with a two-component quantum field, which constitutes a minimal model for spontaneous breaking of a continuous symmetry. Additionally, all microscopic parameters of our system are known from first principles and the resolution of our measurement allows us to detect excited states of the many-body system at the level of individual quasiparticles. This allows for an in-depth study of Higgs excitations that also addresses the consequences of the reduced dimensionality and confinement of the system. Our work constitutes a step towards exploring emergent relativistic models with ultracold atomic gases.

  1. Fitting of m*/m with Divergence Curve for He3 Fluid Monolayer using Hole-driven Mott Transition

    NASA Astrophysics Data System (ADS)

    Kim, Hyun-Tak

    2012-02-01

    The electron-electron interaction for strongly correlated systems plays an important role in formation of an energy gap in solid. The breakdown of the energy gap is called the Mott metal-insulator transition (MIT) which is different from the Peierls MIT induced by breakdown of electron-phonon interaction generated by change of a periodic lattice. It has been known that the correlated systems are inhomogeneous. In particular, He3 fluid monolayer [1] and La1-xSrxTiO3 [2] are representative strongly correlated systems. Their doping dependence of the effective mass of carrier in metal, m*/m, indicating the magnitude of correlation (Coulomb interaction) between electrons has a divergence behavior. However, the fitting remains unfitted to be explained by a Mott-transition theory with divergence. In the case of He3 regarded as the Fermi system with one positive charge (2 electrons + 3 protons), the interaction between He3 atoms is regarded as the correlation in strongly correlated system. In this presentation, we introduce a Hole-driven MIT with a divergence near the Mott transition [3] and fit the m*/m curve in He3 [1] and La1-xSrxTiO3 systems with the Hole-driven MIT with m*/m=1/(1-ρ^4) where ρ is band filling. Moreover, it is shown that the physical meaning of the effective mass with the divergence is percolation in which m*/m increases with increasing doping concentration, and that the magnitude of m*/m is constant.[4pt] [1] Phys. Rev. Lett. 90, 115301 (2003).[0pt] [2] Phys. Rev. Lett. 70, 2126 (1993).[0pt] [3] Physica C 341-348, 259 (2000); Physica C 460-462, 1076 (2007).

  2. Study of Low Energy Electron Inelastic Scattering Mechanisms Using Spin Sensitive Techniques

    NASA Astrophysics Data System (ADS)

    Hsu, Hongbing

    1995-01-01

    Spin sensitive electron spectroscopies were used to study low energy electron inelastic scattering from metal surfaces and thin films. In these experiments, a beam of spin polarized electrons from a GaAs source is directed on the sample surface, and the spin polarization and intensity are measured as a function of energy loss and scattering angle by a Mott electron polarimeter coupled with a concentric hemispherical energy analyzer. Systematic studies of the angular dependence of inelastically scattered electrons were conducted on a Cu(100) surface, and Mo/Cu(100), non-magnetized Fe/Cu(100), and Co/Cu(100) films. The polarization and intensity of scattered electrons were measured as function of energy loss and scattering angle. Further studies were also conducted on Ag(100) surface and amorphous Cu/Ag(100) films. From the experimental results, the angular distributions of dipole and impact scattered electrons can be determined individually and both are found to peak in the specular scattering direction. Preliminary studies were conducted on magnetized Co/Cu(100) films. The spin dependent scattering intensity asymmetry was measured, with a clearly observable peak at energy loss of ~1 eV, which coincides with the band splitting. The polarizations of secondary electrons produced by an unpolarized primary beam were also measured. The polarizations can be related to the band polarization of magnetized cobalt films.

  3. Collapse of the Mott Gap and Emergence of a Nodal Liquid in Lightly Doped Sr(2)IrO(4).

    PubMed

    de la Torre, A; McKeown Walker, S; Bruno, F Y; Riccó, S; Wang, Z; Gutierrez Lezama, I; Scheerer, G; Giriat, G; Jaccard, D; Berthod, C; Kim, T K; Hoesch, M; Hunter, E C; Perry, R S; Tamai, A; Baumberger, F

    2015-10-23

    We report angle resolved photoemission experiments on the electron doped Heisenberg antiferromagnet (Sr(1-x)La(x))(2)IrO(4). For a doping level of x=0.05, we find an unusual metallic state with coherent nodal excitations and an antinodal pseudogap bearing strong similarities with underdoped cuprates. This state emerges from a rapid collapse of the Mott gap with doping resulting in a large underlying Fermi surface that is backfolded by a (π,π) reciprocal lattice vector which we attribute to the intrinsic structural distortion of Sr(2)IrO(4). PMID:26551128

  4. Collapse of the Mott Gap and Emergence of a Nodal Liquid in Lightly Doped Sr(2)IrO(4).

    PubMed

    de la Torre, A; McKeown Walker, S; Bruno, F Y; Riccó, S; Wang, Z; Gutierrez Lezama, I; Scheerer, G; Giriat, G; Jaccard, D; Berthod, C; Kim, T K; Hoesch, M; Hunter, E C; Perry, R S; Tamai, A; Baumberger, F

    2015-10-23

    We report angle resolved photoemission experiments on the electron doped Heisenberg antiferromagnet (Sr(1-x)La(x))(2)IrO(4). For a doping level of x=0.05, we find an unusual metallic state with coherent nodal excitations and an antinodal pseudogap bearing strong similarities with underdoped cuprates. This state emerges from a rapid collapse of the Mott gap with doping resulting in a large underlying Fermi surface that is backfolded by a (π,π) reciprocal lattice vector which we attribute to the intrinsic structural distortion of Sr(2)IrO(4).

  5. Orbital-selective Mott phases of a one-dimensional three-orbital Hubbard model studied using computational techniques

    DOE PAGESBeta

    Liu, Guangkun; Kaushal, Nitin; Liu, Shaozhi; Bishop, Christopher B.; Wang, Yan; Johnston, Steve; Alvarez, Gonzalo; Moreo, Adriana; Dagotto, Elbio R.

    2016-06-24

    A recently introduced one-dimensional three-orbital Hubbard model displays orbital-selective Mott phases with exotic spin arrangements such as spin block states [J. Rincón et al., Phys. Rev. Lett. 112, 106405 (2014)]. In this paper we show that the constrained-path quantum Monte Carlo (CPQMC) technique can accurately reproduce the phase diagram of this multiorbital one-dimensional model, paving the way to future CPQMC studies in systems with more challenging geometries, such as ladders and planes. The success of this approach relies on using the Hartree-Fock technique to prepare the trial states needed in CPQMC. In addition, we study a simplified version of themore » model where the pair-hopping term is neglected and the Hund coupling is restricted to its Ising component. The corresponding phase diagrams are shown to be only mildly affected by the absence of these technically difficult-to-implement terms. This is confirmed by additional density matrix renormalization group and determinant quantum Monte Carlo calculations carried out for the same simplified model, with the latter displaying only mild fermion sign problems. Lastly, we conclude that these methods are able to capture quantitatively the rich physics of the several orbital-selective Mott phases (OSMP) displayed by this model, thus enabling computational studies of the OSMP regime in higher dimensions, beyond static or dynamic mean-field approximations.« less

  6. Effects of higher-order energy bands and temperature on the bosonic Mott insulator in a periodically modulated lattice

    NASA Astrophysics Data System (ADS)

    Sajna, A. S.

    2016-10-01

    We show that a certain class of higher-order excitations in ultracold atoms experiments can be described by straightforward extension of the standard strong coupling approach in the coherent state path integral formalism. It is achieved by theoretical analysis of energy absorption spectroscopy in the three-dimensional system of strongly correlated bosons described by the Bose-Hubbard model. In particular, for unit filling, an explicit form of the single-particle Mott insulator Green function at finite temperatures is derived which goes beyond the standard Hubbard bands description. Moreover, for relevant densities, we calculated the energy absorption rate and performed thermometry on rubidium atomic cloud gas by using previously obtained experimental data. Within the local density approximation, we explain that in such systems the nature of absorption spectrum depends significantly on local chemical potential: (a) the crossover region between lobes is characterized by different types of particle-hole excitations from neighboring Mott lobes and (b) origin of higher-order energy excitations changes from hole type to particle type for higher bosonic densities.

  7. Emergent ``super-solitons'' following an interaction strength quantum quench across a Luttinger liquid-Mott insulating phase boundary

    NASA Astrophysics Data System (ADS)

    Foster, Matthew; Yuzbashyan, Emil

    2010-03-01

    Rapid progress in cold atom experiments has motivated the study of non-equilibrium many-body dynamics following a sudden deformation of the system Hamiltonian (a ``quantum quench''). Here, we consider the dynamics of localized excitations produced via a quench across a quantum phase boundary separating critical Luttinger liquid and gapped Mott insulating states. Our initial liquid ground state is labeled by a Luttinger interaction parameter K, and subject to a density-inhomogeneity forming external potential. For the Mott insulator, we employ the quantum Sine Gordon model at the Luther-Emery (LE) point. We find that over a wide range of initial K values, the quench induces the production of relativistic, non-dispersive traveling density waves, which we dub ``super-solitons.'' The super-solitons are generated from generic antecedent localized density lumps, and appear to be a robust feature of the post-quench dynamics. An isolated exception occurs for the case of K = KLE; here, the density dynamics are generically dispersive, and depend sensitively upon the shape of the initial inhomogeneity. We show that the super-solitons do not interact, and we demonstrate that an inhomogeneous Luttinger parameter K can be used to produce super-solitons with different characteristics in the same system.

  8. Orbital-selective Mott phases of a one-dimensional three-orbital Hubbard model studied using computational techniques

    NASA Astrophysics Data System (ADS)

    Liu, Guangkun; Kaushal, Nitin; Li, Shaozhi; Bishop, Christopher B.; Wang, Yan; Johnston, Steve; Alvarez, Gonzalo; Moreo, Adriana; Dagotto, Elbio

    2016-06-01

    A recently introduced one-dimensional three-orbital Hubbard model displays orbital-selective Mott phases with exotic spin arrangements such as spin block states [J. Rincón et al., Phys. Rev. Lett. 112, 106405 (2014), 10.1103/PhysRevLett.112.106405]. In this publication we show that the constrained-path quantum Monte Carlo (CPQMC) technique can accurately reproduce the phase diagram of this multiorbital one-dimensional model, paving the way to future CPQMC studies in systems with more challenging geometries, such as ladders and planes. The success of this approach relies on using the Hartree-Fock technique to prepare the trial states needed in CPQMC. We also study a simplified version of the model where the pair-hopping term is neglected and the Hund coupling is restricted to its Ising component. The corresponding phase diagrams are shown to be only mildly affected by the absence of these technically difficult-to-implement terms. This is confirmed by additional density matrix renormalization group and determinant quantum Monte Carlo calculations carried out for the same simplified model, with the latter displaying only mild fermion sign problems. We conclude that these methods are able to capture quantitatively the rich physics of the several orbital-selective Mott phases (OSMP) displayed by this model, thus enabling computational studies of the OSMP regime in higher dimensions, beyond static or dynamic mean-field approximations.

  9. Orbital-selective Mott phases of a one-dimensional three-orbital Hubbard model studied using computational techniques.

    PubMed

    Liu, Guangkun; Kaushal, Nitin; Li, Shaozhi; Bishop, Christopher B; Wang, Yan; Johnston, Steve; Alvarez, Gonzalo; Moreo, Adriana; Dagotto, Elbio

    2016-06-01

    A recently introduced one-dimensional three-orbital Hubbard model displays orbital-selective Mott phases with exotic spin arrangements such as spin block states [J. Rincón et al., Phys. Rev. Lett. 112, 106405 (2014)PRLTAO0031-900710.1103/PhysRevLett.112.106405]. In this publication we show that the constrained-path quantum Monte Carlo (CPQMC) technique can accurately reproduce the phase diagram of this multiorbital one-dimensional model, paving the way to future CPQMC studies in systems with more challenging geometries, such as ladders and planes. The success of this approach relies on using the Hartree-Fock technique to prepare the trial states needed in CPQMC. We also study a simplified version of the model where the pair-hopping term is neglected and the Hund coupling is restricted to its Ising component. The corresponding phase diagrams are shown to be only mildly affected by the absence of these technically difficult-to-implement terms. This is confirmed by additional density matrix renormalization group and determinant quantum Monte Carlo calculations carried out for the same simplified model, with the latter displaying only mild fermion sign problems. We conclude that these methods are able to capture quantitatively the rich physics of the several orbital-selective Mott phases (OSMP) displayed by this model, thus enabling computational studies of the OSMP regime in higher dimensions, beyond static or dynamic mean-field approximations. PMID:27415393

  10. Resonant Inelastic X-ray Scattering in Correlated Electron Systems

    NASA Astrophysics Data System (ADS)

    Kim, Young-June

    2006-03-01

    Extremely bright photons generated at the new generation of synchrotron light sources have made a huge impact on various scientific disciplines ranging from biology to materials science. One of the exciting new developments is the use of x-rays in the field of solid-state spectroscopy. Inelastic x-ray scattering, analogous to the well-known inelastic neutron scattering, is a powerful tool for studying momentum-dependent electronic excitations and phonons. In particular, resonant inelastic x-ray scattering in the hard x-ray regime has been widely utilized to study the momentum dependence of various electronic excitations in strongly correlated electron systems. For example, by tuning the incident photon energy to the Cu K-edge, one can gain a large intensity enhancement as well as element specific knowledge of the electronic excitations in various copper oxide compounds. Most of the work to date has been focused on the charge-transfer excitation between the bonding and antibonding molecular orbitals, the excitation across the Mott gap, and crystal field excitations between the d-orbitals. Recent improvements in instrumentation have allowed us to observe a new mode in the mid-infrared frequency region. We will discuss the momentum dependence of these excitations in prototypical cuprate superconductors, La2-xSrxCuO4, and also examine the evolution of such excitations as charge carriers are doped into the system.

  11. Mott Multiferroics and Ferroelectric Metals from Dynamical Mean-Field Theory combined with Density-Functional Theory

    NASA Astrophysics Data System (ADS)

    Capone, Massimo

    2015-03-01

    Multiferroic materials, in which ferroelectricity and long-range magnetic ordering coexist, are natural candidates for applications. In this perspective, the most promising compounds are those in which the two phenomena do not simply coexist, but they influence each other through a magnetoelectric coupling. We present different applications of Density Functional Theory combined with Dynamical Mean-Field Theory in which electron-electron correlation effects are crucial in the stabilization of multiferroic behavior and in the magnetoelectric coupling. Within this wide family we can distinguish different cases. In Sr0.5Ba0.5MnO3 the multiferroic behavior is associated with a Mott insulating state in which the Mn half-filled t2g orbitals are responsible of the magnetic properties and the value of the polarization is strongly affected by the magnetic state. LiOsO3 shares the same electronic configuration with half-filled Os t2g orbitals. Despite this configuration enhances the effect of electron-electron interactions, the material remains metallic and represents a peculiar ferroelectric metal. We propose however how to turn this non-magnetic polar metal into a multiferroic through the design of a superlattice, which increases the degree of correlation, leading to Mott localization of the Os orbitals. In completely different systems, such as organic crystals like (TMTTF)2-X, strong correlations can lead to multiferroicity in organic crystals such as (TMTTF)2-X, where charge ordering promotes a polarization which is favored by an antiferromagnetic ordering. We finally discuss how strong correlations can play a major role away from half-filling when the Hund's coupling is sizable in compounds with a nominal valence of, e.g., two electrons in the three t2g orbitals. Such ``Hund's metals'' are correlated despite being far from Mott localization. This physical regime can be a fertile ground to obtain other ferroelectric metals. This work is supported by ERC/FP7 through the

  12. Mott Peierls phase in deuterated copper-DCNQI systems: a comprehensive study of longitudinal and transverse conductivity and ageing effects

    NASA Astrophysics Data System (ADS)

    Pinteric, Marko; Vuletic, Tomislav; Loncaric, Martin; Petukhov, Konstantin; Gorshunov, Boris; von Schütz, Jost Ulrich; Tomic, Silvia; Dressel, Martin

    2003-11-01

    Transport and low-frequency optical reflection measurements (180-380 GHz) are reported for the quasi-three-dimensional conducting alloy Cu[(2,5(CH3)2-DCNQI)0.70(2,5(CD3)2-DCNQI)0.30]2 between room temperature and 35 K. The optical properties of the system are strongly anisotropic. It is metallic down to 60 K where a Mott-Peierls phase transition occurs. While the transverse conductivity remains practically unchanged, the longitudinal conductivity abruptly drops at the phase transition. Comparing our latest results with previous dc data and measurements of the microwave conductivity also reported here, we find indications of an ageing effect in these samples.

  13. Tuning bad metal and non-Fermi liquid behavior in a Mott material: Rare-earth nickelate thin films.

    PubMed

    Mikheev, Evgeny; Hauser, Adam J; Himmetoglu, Burak; Moreno, Nelson E; Janotti, Anderson; Van de Walle, Chris G; Stemmer, Susanne

    2015-11-01

    Resistances that exceed the Mott-Ioffe-Regel limit (known as bad metal behavior) and non-Fermi liquid behavior are ubiquitous features of the normal state of many strongly correlated materials. We establish the conditions that lead to bad metal and non-Fermi liquid phases in NdNiO3, which exhibits a prototype bandwidth-controlled metal-insulator transition. We show that resistance saturation is determined by the magnitude of Ni eg orbital splitting, which can be tuned by strain in epitaxial films, causing the appearance of bad metal behavior under certain conditions. The results shed light on the nature of a crossover to a non-Fermi liquid metal phase and provide a predictive criterion for Anderson localization. They elucidate a seemingly complex phase behavior as a function of film strain and confinement and provide guidelines for orbital engineering and novel devices. PMID:26601140

  14. Tuning bad metal and non-Fermi liquid behavior in a Mott material: Rare-earth nickelate thin films

    PubMed Central

    Mikheev, Evgeny; Hauser, Adam J.; Himmetoglu, Burak; Moreno, Nelson E.; Janotti, Anderson; Van de Walle, Chris G.; Stemmer, Susanne

    2015-01-01

    Resistances that exceed the Mott-Ioffe-Regel limit (known as bad metal behavior) and non-Fermi liquid behavior are ubiquitous features of the normal state of many strongly correlated materials. We establish the conditions that lead to bad metal and non-Fermi liquid phases in NdNiO3, which exhibits a prototype bandwidth-controlled metal-insulator transition. We show that resistance saturation is determined by the magnitude of Ni eg orbital splitting, which can be tuned by strain in epitaxial films, causing the appearance of bad metal behavior under certain conditions. The results shed light on the nature of a crossover to a non-Fermi liquid metal phase and provide a predictive criterion for Anderson localization. They elucidate a seemingly complex phase behavior as a function of film strain and confinement and provide guidelines for orbital engineering and novel devices. PMID:26601140

  15. Tuning bad metal and non-Fermi liquid behavior in a Mott material: Rare-earth nickelate thin films.

    PubMed

    Mikheev, Evgeny; Hauser, Adam J; Himmetoglu, Burak; Moreno, Nelson E; Janotti, Anderson; Van de Walle, Chris G; Stemmer, Susanne

    2015-11-01

    Resistances that exceed the Mott-Ioffe-Regel limit (known as bad metal behavior) and non-Fermi liquid behavior are ubiquitous features of the normal state of many strongly correlated materials. We establish the conditions that lead to bad metal and non-Fermi liquid phases in NdNiO3, which exhibits a prototype bandwidth-controlled metal-insulator transition. We show that resistance saturation is determined by the magnitude of Ni eg orbital splitting, which can be tuned by strain in epitaxial films, causing the appearance of bad metal behavior under certain conditions. The results shed light on the nature of a crossover to a non-Fermi liquid metal phase and provide a predictive criterion for Anderson localization. They elucidate a seemingly complex phase behavior as a function of film strain and confinement and provide guidelines for orbital engineering and novel devices.

  16. Wigner-Mott insulator-to-insulator transition at pressure in charge-ordered Fe2OBO3

    NASA Astrophysics Data System (ADS)

    Diguet, G.; Hearne, G. R.; Sibanda, W. N.; Carleschi, E.; Musyimi, P.; Pischedda, V.; Attfield, J. P.

    2014-01-01

    Magnetic-electronic studies of mixed-valence Fe2OBO3 have shown that ionic charge order (CO) is disrupted at ˜16 GPa. The pertinent minority-spin carrier exhibits persistent intersite electron exchange Fe2+ ⇔ Fe3+ to well beyond this pressure. Temperature-dependent electrical transport measurements over an extended pressure range presented here demonstrate that the electronic structure remains gapped to well beyond 16 GPa. Extrapolation of data to higher pressure suggests that metallization will only prevail at P>50 GPa. Both the persistent gapped electronic state across the CO instability and signature of carrier confinement to Fe-Fe dimers in the Fe2+ ⇔ Fe3+ electron exchange are rationalized as crossover from a Wigner crystal (site centered) insulator to a dimer Mott (bond centered type) insulator—"Wigner-Mott transition" at ˜16 GPa. The dimer insulating state is a consequence of modulation of the relevant hopping parameter t in quasi-low-dimensional features in the structure (ribbons and chains). Complementary structural studies suggest that the a axis is appreciably more compressible than other crystallographic directions of the original monoclinic unit cell. Therefore, such a modulation in t may arise from Peierls type distortions along the a axis or else stems from intrinsic modulation in the c axis direction of the unit cell. This is aided by a monoclinic (P21/c) → orthorhombic (Pmcn) structural adjustment that is concurrent across the electronic transition. Pressure tuning of relative values of on-site U/t and intersite V/t Coulomb interaction parameters of the quasi-low-dimensional features evolve the system from site-centered to dimer-centered electron localization.

  17. James C. McGroddy Prize for New Materials Talk: What is new in multiferroicity?: Mott ferroelectrics!

    NASA Astrophysics Data System (ADS)

    Cheong, Sang-Wook

    2010-03-01

    Multiferroicity is an old topic. For example, linear magnetoelectric effect in materials such as Cr2O3 with broken time reversal and space inversion symmetry has been known since 1960's. However, giant cross-coupling effects such as flipping polarization or enormous change of dielectric constant by applied magnetic fields have been recently observed in systems such as Tb(Dy)MnO3 and Tb(Dy)Mn2O5 [1-3]. The important ingredient for these giant magnetoelectric effects turns out to be associated with the presence of non-zero d electrons and their mutual interactions, leading to the Mott-insulator-type charge gap, magnetism, and collective phase transitions. Particularly, the collective nature of simultaneous magnetic-ferroelectric phase transitions results in the giant magnetoelectric effects. In addition, fascinating charge transport properties such as a switchable photovoltaic effect and characteristic conduction properties at domain walls stem from the (carrier-doped) Mott insulating nature of compounds such as BiFeO3 and hexagonal YMnO3 [4,5]. [4pt] [1] Kimura, T. et al. Magnetic control of ferroelectric polarization. Nature 426, 55--58 (2003).[0pt] [2] Hur, N. et al. Electric polarization reversal and memory in a multiferroic material induced by magnetic fields. Nature 429, 392--395 (2004).[0pt] [3] Cheong, S.-W. & Mostovoy, M. Multiferroics: a magnetic twist for ferroelectricity. Nature Mater. 6, 13--20 (2007).[0pt] [4] Seidel, J. et al. Conduction at domain walls in oxide multiferroics. Nature Mater. 8, 229--234 (2009).[0pt] [5] Choi, T., Lee, S., Choi, Y.J., Kiryukhin, V. & Cheong, S.-W. Switchable ferroelectric diode and photovoltaic effect in BiFeO3. Science 324, 63--66 (2009)

  18. Block Magnetic Excitations in the Orbitally Selective Mott Insulator BaFe2Se3

    NASA Astrophysics Data System (ADS)

    Mourigal, M.; Wu, Shan; Stone, M. B.; Neilson, J. R.; Caron, J. M.; McQueen, T. M.; Broholm, C. L.

    2015-07-01

    Iron pnictides and selenides display a variety of unusual magnetic phases originating from the interplay between electronic, orbital, and lattice degrees of freedom. Using powder inelastic neutron scattering on the two-leg ladder BaFe2Se3 , we fully characterize the static and dynamic spin correlations associated with the Fe4 block state, an exotic magnetic ground state observed in this low-dimensional magnet and in Rb0.89Fe1.58Se2 . All the magnetic excitations of the Fe4 block state predicted by an effective Heisenberg model with localized spins are observed below 300 meV and quantitatively reproduced. However, the data only account for 16 (3 )μB2 per Fe2 + , approximatively 2 /3 of the total spectral weight expected for localized S =2 moments. Our results highlight how orbital degrees of freedom in iron-based magnets can conspire to stabilize an exotic magnetic state.

  19. Pressure-dependent relaxation in the photoexcited mott insulator ET-F2TCNQ: influence of hopping and correlations on quasiparticle recombination rates.

    PubMed

    Mitrano, M; Cotugno, G; Clark, S R; Singla, R; Kaiser, S; Stähler, J; Beyer, R; Dressel, M; Baldassarre, L; Nicoletti, D; Perucchi, A; Hasegawa, T; Okamoto, H; Jaksch, D; Cavalleri, A

    2014-03-21

    We measure the ultrafast recombination of photoexcited quasiparticles (holon-doublon pairs) in the one dimensional Mott insulator ET-F(2)TCNQ as a function of external pressure, which is used to tune the electronic structure. At each pressure value, we first fit the static optical properties and extract the electronic bandwidth t and the intersite correlation energy V. We then measure the recombination times as a function of pressure, and we correlate them with the corresponding microscopic parameters. We find that the recombination times scale differently than for metals and semiconductors. A fit to our data based on the time-dependent extended Hubbard Hamiltonian suggests that the competition between local recombination and delocalization of the Mott-Hubbard exciton dictates the efficiency of the recombination.

  20. Anion effects on electronic structure and electrodynamic properties of the Mott insulator κ -(BEDT-TTF ) 2Ag2(CN) 3

    NASA Astrophysics Data System (ADS)

    Pinterić, M.; Lazić, P.; Pustogow, A.; Ivek, T.; Kuveždić, M.; Milat, O.; Gumhalter, B.; Basletić, M.; Čulo, M.; Korin-Hamzić, B.; Löhle, A.; Hübner, R.; Sanz Alonso, M.; Hiramatsu, T.; Yoshida, Y.; Saito, G.; Dressel, M.; Tomić, S.

    2016-10-01

    The Mott insulator κ -(BEDT-TTF ) 2Ag2(CN) 3 forms a highly-frustrated triangular lattice of S =1 /2 dimers with a possible quantum-spin-liquid state. Our experimental and numerical studies reveal the emergence of a slight charge imbalance between crystallographically inequivalent sites, relaxor dielectric response, and hopping dc transport. In a broader perspective we conclude that the universal properties of strongly-correlated charge-transfer salts with spin liquid state are an anion-supported valence band and cyanide-induced quasidegenerate electronic configurations in the relaxed state. The generic low-energy excitations are caused by charged domain walls rather than by fluctuating electric dipoles. They give rise to glassy dynamics characteristic of dimerized Mott insulators, including the sibling compound κ -(BEDT-TTF)2Cu2 (CN )3.

  1. Optical conductivity measurements of GaTa4Se8 under high pressure: evidence of a bandwidth-controlled insulator-to-metal Mott transition.

    PubMed

    Ta Phuoc, V; Vaju, C; Corraze, B; Sopracase, R; Perucchi, A; Marini, C; Postorino, P; Chligui, M; Lupi, S; Janod, E; Cario, L

    2013-01-18

    The optical properties of a GaTa(4)Se(8) single crystal are investigated under high pressure. At ambient pressure, the optical conductivity exhibits a charge gap of ≈0.12 eV and a broad midinfrared band at ≈0.55 eV. As pressure is increased, the low energy spectral weight is strongly enhanced and the optical gap is rapidly filled, pointing to an insulator to metal transition around 6 GPa. The overall evolution of the optical conductivity demonstrates that GaTa(4)Se(8) is a Mott insulator which undergoes a bandwidth-controlled Mott metal-insulator transition under pressure, in remarkably good agreement with theory. With the use of our optical data and ab initio band structure calculations, our results were successfully compared to the (U/D, T/D) phase diagram predicted by dynamical mean field theory for strongly correlated systems.

  2. Scattering from binary optics

    NASA Technical Reports Server (NTRS)

    Ricks, Douglas W.

    1993-01-01

    There are a number of sources of scattering in binary optics: etch depth errors, line edge errors, quantization errors, roughness, and the binary approximation to the ideal surface. These sources of scattering can be systematic (deterministic) or random. In this paper, scattering formulas for both systematic and random errors are derived using Fourier optics. These formulas can be used to explain the results of scattering measurements and computer simulations.

  3. Approximations for photoelectron scattering

    NASA Astrophysics Data System (ADS)

    Fritzsche, V.

    1989-04-01

    The errors of several approximations in the theoretical approach of photoelectron scattering are systematically studied, in tungsten, for electron energies ranging from 10 to 1000 eV. The large inaccuracies of the plane-wave approximation (PWA) are substantially reduced by means of effective scattering amplitudes in the modified small-scattering-centre approximation (MSSCA). The reduced angular momentum expansion (RAME) is so accurate that it allows reliable calculations of multiple-scattering contributions for all the energies considered.

  4. Oxygen-doped Mott-Hubbard cuprate superconductor La1.85Y0.15CuO4-δ from transport measurements

    NASA Astrophysics Data System (ADS)

    Yu, W.; Liang, B.; Li, P.; Fujino, S.; Murakami, T.; Takeuchi, I.; Greene, R. L.

    2007-01-01

    We report resistivity, Hall effect, Nernst effect, and magnetoresistance measurements on T' -phase La1.85Y0.15CuO4-δ (LYCO) films prepared by pulsed laser deposition under different oxygen conditions. Our results show that superconductivity in LYCO originates from an oxygen-doped Mott-like insulator and not from a weakly correlated, half-filled band metal as proposed previously.

  5. Superconducting dome in doped quasi-two-dimensional organic Mott insulators: A paradigm for strongly correlated superconductivity

    NASA Astrophysics Data System (ADS)

    Hébert, Charles-David; Sémon, Patrick; Tremblay, A.-M. S.

    2015-11-01

    Layered organic superconductors of the BEDT family are model systems for understanding the interplay of the Mott transition with superconductivity, magnetic order, and frustration, ingredients that are essential to understand superconductivity also in the cuprate high-temperature superconductors. Recent experimental studies on a hole-doped version of the organic compounds reveals an enhancement of superconductivity and a rapid crossover between two different conducting phases above the superconducting dome. One of these phases is a Fermi liquid, the other not. Using plaquette cellular dynamical mean field theory with state-of-the-art continuous-time quantum Monte Carlo calculations, we study this problem with the two-dimensional Hubbard model on the anisotropic triangular lattice. Phase diagrams as a function of temperature T and interaction strength U /t are obtained for anisotropy parameters t'=0.4 t ,t'=0.8 t and for various fillings. As in the case of the cuprates, we find, at finite doping, a first-order transition between two normal-state phases. One of theses phases has a pseudogap while the other does not. At temperatures above the critical point of the first-order transition, there is a Widom line where crossovers occur. The maximum (optimal) superconducting critical temperature Tcm at finite doping is enhanced by about 25% compared with its maximum at half filling and the range of U /t where superconductivity appears is greatly extended. These results are in broad agreement with experiment. Also, increasing frustration (larger t'/t ) significantly reduces magnetic ordering, as expected. This suggests that for compounds with intermediate to high frustration, very light doping should reveal the influence of the first-order transition and associated crossovers. These crossovers could possibly be even visible in the superconducting phase through subtle signatures. We also predict that destroying the superconducting phase by a magnetic field should reveal the

  6. Scattering in optical materials

    SciTech Connect

    Musikant, S.

    1983-01-01

    Topics discussed include internal scattering and surface scattering, environmental effects, and various applications. Papers are presented on scattering in ZnSe laser windows, the far-infrared reflectance spectra of optical black coatings, the effects of standard optical shop practices on scattering, and the damage susceptibility of ring laser gyro class optics. Attention is also given to the infrared laser stimulated desorption of pyridine from silver surfaces, to electrically conductive black optical paint, to light scattering from an interface bubble, and to the role of diagnostic testing in identifying and resolving dimensional stability problems in electroplated laser mirrors.

  7. Electric double-layer transistor using layered iron selenide Mott insulator TlFe1.6Se2.

    PubMed

    Katase, Takayoshi; Hiramatsu, Hidenori; Kamiya, Toshio; Hosono, Hideo

    2014-03-18

    A(1-x)Fe(2-y)Se2 (A = K, Cs, Rb, Tl) are recently discovered iron-based superconductors with critical temperatures (Tc) ranging up to 32 K. Their parent phases have unique properties compared with other iron-based superconductors; e.g., their crystal structures include ordered Fe vacancies, their normal states are antiferromagnetic (AFM) insulating phases, and they have extremely high Néel transition temperatures. However, control of carrier doping into the parent AFM insulators has been difficult due to their intrinsic phase separation. Here, we fabricated an Fe-vacancy-ordered TlFe1.6Se2 insulating epitaxial film with an atomically flat surface and examined its electrostatic carrier doping using an electric double-layer transistor (EDLT) structure with an ionic liquid gate. The positive gate voltage gave a conductance modulation of three orders of magnitude at 25 K, and further induced and manipulated a phase transition; i.e., delocalized carrier generation by electrostatic doping is the origin of the phase transition. This is the first demonstration, to the authors' knowledge, of an EDLT using a Mott insulator iron selenide channel and opens a way to explore high Tc superconductivity in iron-based layered materials, where carrier doping by conventional chemical means is difficult.

  8. Engineered Mott ground state in a LaTiO3+δ/LaNiO3 heterostructure

    DOE PAGESBeta

    Cao, Yanwei; Liu, Xiaoran; Kareev, M.; Choudhury, D.; Middey, S.; Meyers, D.; Kim, J. -W.; Ryan, P. J.; Freeland, J. W.; Chakhalian, J.

    2016-01-21

    In pursuit of creating cuprate-like electronic and orbital structures, artificial heterostructures based on LaNiO3 have inspired a wealth of exciting experimental and theoretical results. However, to date there is a very limited experimental understanding of the electronic and orbital states emerging from interfacial charge transfer and their connections to the modified band structure at the interface. Towards this goal, we have synthesized a prototypical superlattice composed of a correlated metal LaNiO3 and a doped Mott insulator LaTiO3+δ, and investigated its electronic structure by resonant X-ray absorption spectroscopy combined with X-ray photoemission spectroscopy, electrical transport and theory calculations. The heterostructure exhibitsmore » interfacial charge transfer from Ti to Ni sites, giving rise to an insulating ground state with orbital polarization and eg orbital band splitting. Here, our findings demonstrate how the control over charge at the interface can be effectively used to create exotic electronic, orbital and spin states.« less

  9. Superconductor to Mott insulator transition in YBa2Cu3O7/LaCaMnO3 heterostructures

    PubMed Central

    Gray, B. A.; Middey, S.; Conti, G.; Gray, A. X.; Kuo, C.-T.; Kaiser, A. M.; Ueda, S.; Kobayashi, K.; Meyers, D.; Kareev, M.; Tung, I. C.; Liu, Jian; Fadley, C. S.; Chakhalian, J.; Freeland, J. W.

    2016-01-01

    The superconductor-to-insulator transition (SIT) induced by means such as external magnetic fields, disorder or spatial confinement is a vivid illustration of a quantum phase transition dramatically affecting the superconducting order parameter. In pursuit of a new realization of the SIT by interfacial charge transfer, we developed extremely thin superlattices composed of high Tc superconductor YBa2Cu3O7 (YBCO) and colossal magnetoresistance ferromagnet La0.67Ca0.33MnO3 (LCMO). By using linearly polarized resonant X-ray absorption spectroscopy and magnetic circular dichroism, combined with hard X-ray photoelectron spectroscopy, we derived a complete picture of the interfacial carrier doping in cuprate and manganite atomic layers, leading to the transition from superconducting to an unusual Mott insulating state emerging with the increase of LCMO layer thickness. In addition, contrary to the common perception that only transition metal ions may respond to the charge transfer process, we found that charge is also actively compensated by rare-earth and alkaline-earth metal ions of the interface. Such deterministic control of Tc by pure electronic doping without any hindering effects of chemical substitution is another promising route to disentangle the role of disorder on the pseudo-gap and charge density wave phases of underdoped cuprates. PMID:27627855

  10. Fractional Mott insulator-to-superfluid transition of Bose-Hubbard model in a trimerized Kagomé optical lattice

    NASA Astrophysics Data System (ADS)

    Chen, Qi-Hui; Li, Peng; Su, Haibin

    2016-06-01

    By generalizing the traditional single-site strong coupling expansion approach to a cluster one, we study the zero-temperature phase diagram of bosonic atoms in a trimerized Kagomé optical lattice. Some new features are present in this system. Due to the strong intra-trimer hopping interaction, there will be a new Mott insulator (MI), which is by definition incompressible but with a fractional filling per trimer. This is different from the traditional MI, which has an integral filling and originates only from the repulsive interaction between particles. We investigate the MI-to-superfluid transition and the nature of the fractional MI by calculating the critical exponents of phase transitions and the low-lying energy excitation spectra of quasiparticles (quasihole). We will show how the low-energy properties of this system can be understood qualitatively as a Bose-Hubbard model in triangular lattice from the point of view of the cluster strong coupling expansion. We also discuss how our results are related to experiment by studying the Bragg spectroscopy.

  11. Slater to Mott Crossover in the Metal to Insulator Transition of Nd2Ir2O7

    NASA Astrophysics Data System (ADS)

    Nakayama, M.; Kondo, Takeshi; Tian, Z.; Ishikawa, J. J.; Halim, M.; Bareille, C.; Malaeb, W.; Kuroda, K.; Tomita, T.; Ideta, S.; Tanaka, K.; Matsunami, M.; Kimura, S.; Inami, N.; Ono, K.; Kumigashira, H.; Balents, L.; Nakatsuji, S.; Shin, S.

    2016-07-01

    We present an angle-resolved photoemission study of the electronic structure of the three-dimensional pyrochlore iridate Nd2Ir2O7 through its magnetic metal-insulator transition. Our data reveal that metallic Nd2Ir2O7 has a quadratic band, touching the Fermi level at the Γ point, similar to that of Pr2Ir2O7 . The Fermi node state is, therefore, a common feature of the metallic phase of the pyrochlore iridates. Upon cooling below the transition temperature, this compound exhibits a gap opening with an energy shift of quasiparticle peaks like a band gap insulator. The quasiparticle peaks are strongly suppressed, however, with further decrease of temperature, and eventually vanish at the lowest temperature, leaving a nondispersive flat band lacking long-lived electrons. We thereby identify a remarkable crossover from Slater to Mott insulators with decreasing temperature. These observations explain the puzzling absence of Weyl points in this material, despite its proximity to the zero temperature metal-insulator transition.

  12. Engineered Mott ground state in a LaTiO3+δ/LaNiO3 heterostructure

    PubMed Central

    Cao, Yanwei; Liu, Xiaoran; Kareev, M.; Choudhury, D.; Middey, S.; Meyers, D.; Kim, J.-W.; Ryan, P. J.; Freeland, J.W.; Chakhalian, J.

    2016-01-01

    In pursuit of creating cuprate-like electronic and orbital structures, artificial heterostructures based on LaNiO3 have inspired a wealth of exciting experimental and theoretical results. However, to date there is a very limited experimental understanding of the electronic and orbital states emerging from interfacial charge transfer and their connections to the modified band structure at the interface. Towards this goal, we have synthesized a prototypical superlattice composed of a correlated metal LaNiO3 and a doped Mott insulator LaTiO3+δ, and investigated its electronic structure by resonant X-ray absorption spectroscopy combined with X-ray photoemission spectroscopy, electrical transport and theory calculations. The heterostructure exhibits interfacial charge transfer from Ti to Ni sites, giving rise to an insulating ground state with orbital polarization and eg orbital band splitting. Our findings demonstrate how the control over charge at the interface can be effectively used to create exotic electronic, orbital and spin states. PMID:26791402

  13. DSMC-CFD Comparison of a High Altitude, Hypersonic Reentry Flow Using the Mott-Smith Model

    NASA Astrophysics Data System (ADS)

    Ozawa, T.; Nompelis, I.; Levin, D. A.; Barnhardt, M.; Candler, G. V.

    2008-12-01

    Stardust reentry flows have been simulated at 80 km altitude, 12.8 km/s, using the direct simulation Monte Carlo (DSMC) and computational fluid dynamics (CFD). Neutral and ionization processes among neutral air species, as well as five ionic species and electrons were considered in the DSMC flowfield modeling using the ion-averaged velocity model to maintain charge-neutrality. In CFD, two electron temperature models were compared, and it was found that the degree of ionization (DOI) is sensitive to the electron temperature model. At 80 km, the DOI predicted by DSMC was found to be approximately 3%, but in CFD, the DOI is greater than 20% for the case of Te = Ttr and 9% for the case of Te = Tvib. Therefore, compared to the DSMC solution, the assumption of Te = Tvib is preferable in CFD. Using the Mott-Smith (M-S) model, good agreement was obtained between the analytical bimodal distribution functions and DSMC velocity distributions. An effective temperature correction in the relaxation and chemical reaction models using the M-S model was developed in CFD, and the model reduced the continuum breakdown discrepancy between DSMC and CFD inside the shock in terms of DOI and temperatures. With the M-S model, the DOI for the case of Te = Tvib in CFD is decreased by approximately 3%.

  14. Superconductor to Mott insulator transition in YBa2Cu3O7/LaCaMnO3 heterostructures.

    PubMed

    Gray, B A; Middey, S; Conti, G; Gray, A X; Kuo, C-T; Kaiser, A M; Ueda, S; Kobayashi, K; Meyers, D; Kareev, M; Tung, I C; Liu, Jian; Fadley, C S; Chakhalian, J; Freeland, J W

    2016-01-01

    The superconductor-to-insulator transition (SIT) induced by means such as external magnetic fields, disorder or spatial confinement is a vivid illustration of a quantum phase transition dramatically affecting the superconducting order parameter. In pursuit of a new realization of the SIT by interfacial charge transfer, we developed extremely thin superlattices composed of high Tc superconductor YBa2Cu3O7 (YBCO) and colossal magnetoresistance ferromagnet La0.67Ca0.33MnO3 (LCMO). By using linearly polarized resonant X-ray absorption spectroscopy and magnetic circular dichroism, combined with hard X-ray photoelectron spectroscopy, we derived a complete picture of the interfacial carrier doping in cuprate and manganite atomic layers, leading to the transition from superconducting to an unusual Mott insulating state emerging with the increase of LCMO layer thickness. In addition, contrary to the common perception that only transition metal ions may respond to the charge transfer process, we found that charge is also actively compensated by rare-earth and alkaline-earth metal ions of the interface. Such deterministic control of Tc by pure electronic doping without any hindering effects of chemical substitution is another promising route to disentangle the role of disorder on the pseudo-gap and charge density wave phases of underdoped cuprates. PMID:27627855

  15. Large epitaxial bi-axial strain induces a Mott-like phase transition in VO{sub 2}

    SciTech Connect

    Kittiwatanakul, Salinporn; Wolf, Stuart A.; Lu, Jiwei

    2014-08-18

    The metal insulator transition (MIT) in vanadium dioxide (VO{sub 2}) has been an important topic for recent years. It has been generally agreed upon that the mechanism of the MIT in bulk VO{sub 2} is considered to be a collaborative Mott-Peierls transition, however, the effect of strain on the phase transition is much more complicated. In this study, the effect of the large strain on the properties of VO{sub 2} films was investigated. One remarkable result is that highly strained epitaxial VO{sub 2} thin films were rutile in the insulating state as well as in the metallic state. These highly strained VO{sub 2} films underwent an electronic phase transition without the concomitant Peierls transition. Our results also show that a very large tensile strain along the c-axis of rutile VO{sub 2} resulted in a phase transition temperature of ∼433 K, much higher than in any previous report. Our findings elicit that the metal insulator transition in VO{sub 2} can be driven by an electronic transition alone, rather the typical coupled electronic-structural transition.

  16. Engineered Mott ground state in a LaTiO3+δ/LaNiO3 heterostructure

    NASA Astrophysics Data System (ADS)

    Cao, Yanwei; Liu, Xiaoran; Kareev, M.; Choudhury, D.; Middey, S.; Meyers, D.; Kim, J.-W.; Ryan, P. J.; Freeland, J. W.; Chakhalian, J.

    2016-01-01

    In pursuit of creating cuprate-like electronic and orbital structures, artificial heterostructures based on LaNiO3 have inspired a wealth of exciting experimental and theoretical results. However, to date there is a very limited experimental understanding of the electronic and orbital states emerging from interfacial charge transfer and their connections to the modified band structure at the interface. Towards this goal, we have synthesized a prototypical superlattice composed of a correlated metal LaNiO3 and a doped Mott insulator LaTiO3+δ, and investigated its electronic structure by resonant X-ray absorption spectroscopy combined with X-ray photoemission spectroscopy, electrical transport and theory calculations. The heterostructure exhibits interfacial charge transfer from Ti to Ni sites, giving rise to an insulating ground state with orbital polarization and eg orbital band splitting. Our findings demonstrate how the control over charge at the interface can be effectively used to create exotic electronic, orbital and spin states.

  17. Superconductor to Mott insulator transition in YBa2Cu3O7/LaCaMnO3 heterostructures

    DOE PAGESBeta

    Gray, B. A.; Middey, S.; Conti, G.; Gray, A. X.; Kuo, C. -T.; Kaiser, A. M.; Ueda, S.; Kobayashi, K.; Meyers, D.; Kareev, M.; et al

    2016-09-15

    The superconductor-to-insulator transition (SIT) induced by means such as external magnetic fields, disorder or spatial confinement is a vivid illustration of a quantum phase transition dramatically affecting the superconducting order parameter. In this paper, in pursuit of a new realization of the SIT by interfacial charge transfer, we developed extremely thin superlattices composed of high Tc superconductor YBa2Cu3O7 (YBCO) and colossal magnetoresistance ferromagnet La0.67Ca0.33MnO3 (LCMO). By using linearly polarized resonant X-ray absorption spectroscopy and magnetic circular dichroism, combined with hard X-ray photoelectron spectroscopy, we derived a complete picture of the interfacial carrier doping in cuprate and manganite atomic layers, leadingmore » to the transition from superconducting to an unusual Mott insulating state emerging with the increase of LCMO layer thickness. In addition, contrary to the common perception that only transition metal ions may respond to the charge transfer process, we found that charge is also actively compensated by rare-earth and alkaline-earth metal ions of the interface. Finally, such deterministic control of Tc by pure electronic doping without any hindering effects of chemical substitution is another promising route to disentangle the role of disorder on the pseudo-gap and charge density wave phases of underdoped cuprates.« less

  18. Fractional Mott insulator-to-superfluid transition of Bose–Hubbard model in a trimerized Kagomé optical lattice

    NASA Astrophysics Data System (ADS)

    Chen, Qi-Hui; Li, Peng; Su, Haibin

    2016-06-01

    By generalizing the traditional single-site strong coupling expansion approach to a cluster one, we study the zero-temperature phase diagram of bosonic atoms in a trimerized Kagomé optical lattice. Some new features are present in this system. Due to the strong intra-trimer hopping interaction, there will be a new Mott insulator (MI), which is by definition incompressible but with a fractional filling per trimer. This is different from the traditional MI, which has an integral filling and originates only from the repulsive interaction between particles. We investigate the MI-to-superfluid transition and the nature of the fractional MI by calculating the critical exponents of phase transitions and the low-lying energy excitation spectra of quasiparticles (quasihole). We will show how the low-energy properties of this system can be understood qualitatively as a Bose–Hubbard model in triangular lattice from the point of view of the cluster strong coupling expansion. We also discuss how our results are related to experiment by studying the Bragg spectroscopy.

  19. Negative activation energy and dielectric signatures of excitons and excitonic Mott transitions in quantum confined laser structures

    NASA Astrophysics Data System (ADS)

    Bhunia, Amit; Bansal, Kanika; Henini, Mohamed; Alshammari, Marzook S.; Datta, Shouvik

    2016-10-01

    Mostly, optical spectroscopies are used to investigate the physics of excitons, whereas their electrical evidences are hardly explored. Here, we examined a forward bias activated differential capacitance response of GaInP/AlGaInP based multi-quantum well laser diodes to trace the presence of excitons using electrical measurements. Occurrence of "negative activation energy" after light emission is understood as thermodynamical signature of steady state excitonic population under intermediate range of carrier injections. Similar corroborative results are also observed in an InGaAs/GaAs quantum dot laser structure grown by molecular beam epitaxy. With increasing biases, the measured differential capacitance response slowly vanishes. This represents gradual Mott transition of an excitonic phase into an electron-hole plasma in a GaInP/AlGaInP laser diode. This is further substantiated by more and more exponentially looking shapes of high energy tails in electroluminescence spectra with increasing forward bias, which originates from a growing non-degenerate population of free electrons and holes. Such an experimental correlation between electrical and optical properties of excitons can be used to advance the next generation excitonic devices.

  20. Superconductor to Mott insulator transition in YBa2Cu3O7/LaCaMnO3 heterostructures

    NASA Astrophysics Data System (ADS)

    Gray, B. A.; Middey, S.; Conti, G.; Gray, A. X.; Kuo, C.-T.; Kaiser, A. M.; Ueda, S.; Kobayashi, K.; Meyers, D.; Kareev, M.; Tung, I. C.; Liu, Jian; Fadley, C. S.; Chakhalian, J.; Freeland, J. W.

    2016-09-01

    The superconductor-to-insulator transition (SIT) induced by means such as external magnetic fields, disorder or spatial confinement is a vivid illustration of a quantum phase transition dramatically affecting the superconducting order parameter. In pursuit of a new realization of the SIT by interfacial charge transfer, we developed extremely thin superlattices composed of high Tc superconductor YBa2Cu3O7 (YBCO) and colossal magnetoresistance ferromagnet La0.67Ca0.33MnO3 (LCMO). By using linearly polarized resonant X-ray absorption spectroscopy and magnetic circular dichroism, combined with hard X-ray photoelectron spectroscopy, we derived a complete picture of the interfacial carrier doping in cuprate and manganite atomic layers, leading to the transition from superconducting to an unusual Mott insulating state emerging with the increase of LCMO layer thickness. In addition, contrary to the common perception that only transition metal ions may respond to the charge transfer process, we found that charge is also actively compensated by rare-earth and alkaline-earth metal ions of the interface. Such deterministic control of Tc by pure electronic doping without any hindering effects of chemical substitution is another promising route to disentangle the role of disorder on the pseudo-gap and charge density wave phases of underdoped cuprates.

  1. Slater to Mott Crossover in the Metal to Insulator Transition of Nd_{2}Ir_{2}O_{7}.

    PubMed

    Nakayama, M; Kondo, Takeshi; Tian, Z; Ishikawa, J J; Halim, M; Bareille, C; Malaeb, W; Kuroda, K; Tomita, T; Ideta, S; Tanaka, K; Matsunami, M; Kimura, S; Inami, N; Ono, K; Kumigashira, H; Balents, L; Nakatsuji, S; Shin, S

    2016-07-29

    We present an angle-resolved photoemission study of the electronic structure of the three-dimensional pyrochlore iridate Nd_{2}Ir_{2}O_{7} through its magnetic metal-insulator transition. Our data reveal that metallic Nd_{2}Ir_{2}O_{7} has a quadratic band, touching the Fermi level at the Γ point, similar to that of Pr_{2}Ir_{2}O_{7}. The Fermi node state is, therefore, a common feature of the metallic phase of the pyrochlore iridates. Upon cooling below the transition temperature, this compound exhibits a gap opening with an energy shift of quasiparticle peaks like a band gap insulator. The quasiparticle peaks are strongly suppressed, however, with further decrease of temperature, and eventually vanish at the lowest temperature, leaving a nondispersive flat band lacking long-lived electrons. We thereby identify a remarkable crossover from Slater to Mott insulators with decreasing temperature. These observations explain the puzzling absence of Weyl points in this material, despite its proximity to the zero temperature metal-insulator transition. PMID:27517783

  2. Superconductor to Mott insulator transition in YBa2Cu3O7/LaCaMnO3 heterostructures.

    PubMed

    Gray, B A; Middey, S; Conti, G; Gray, A X; Kuo, C-T; Kaiser, A M; Ueda, S; Kobayashi, K; Meyers, D; Kareev, M; Tung, I C; Liu, Jian; Fadley, C S; Chakhalian, J; Freeland, J W

    2016-01-01

    The superconductor-to-insulator transition (SIT) induced by means such as external magnetic fields, disorder or spatial confinement is a vivid illustration of a quantum phase transition dramatically affecting the superconducting order parameter. In pursuit of a new realization of the SIT by interfacial charge transfer, we developed extremely thin superlattices composed of high Tc superconductor YBa2Cu3O7 (YBCO) and colossal magnetoresistance ferromagnet La0.67Ca0.33MnO3 (LCMO). By using linearly polarized resonant X-ray absorption spectroscopy and magnetic circular dichroism, combined with hard X-ray photoelectron spectroscopy, we derived a complete picture of the interfacial carrier doping in cuprate and manganite atomic layers, leading to the transition from superconducting to an unusual Mott insulating state emerging with the increase of LCMO layer thickness. In addition, contrary to the common perception that only transition metal ions may respond to the charge transfer process, we found that charge is also actively compensated by rare-earth and alkaline-earth metal ions of the interface. Such deterministic control of Tc by pure electronic doping without any hindering effects of chemical substitution is another promising route to disentangle the role of disorder on the pseudo-gap and charge density wave phases of underdoped cuprates.

  3. Crossover from Mott to Efros-Shklovskii variable-range-hopping conductivity in InxOy films

    NASA Astrophysics Data System (ADS)

    Rosenbaum, Ralph

    1991-08-01

    Crossover from Mott variable-range-hopping conductivity to the Coulomb-gap Efros-Shklovskii (ES) variable-range-hopping conductivity has been observed in amorphous indium oxide films. The hopping exponent x~=0.56 in the activated Coulomb-gap regime is greater than the x=0.50 value predicted by Efros and Shklovskii. The experimental value of x~=0.56 is in excellent agreement with the computational calculations of Mobius and Richter, who suggest that x=0.55. The experimental ratios for TMott/TES~=54 are in close agreement with the prediction of Castner that TMott/TES=81. Experimental values for the crossover temperatures, which separate the two hopping regimes, are consistent with predicted values. The Coulomb-gap energy ΔCG is estimated to range from a few tenths of a meV for films close to the metal-insulator transition to several meV's for films quite deep in the insulating regime.

  4. Vacuum polarization in sub-coulomb 12C- 12C scattering (II)

    NASA Astrophysics Data System (ADS)

    Trautmann, D.; Baur, G.; Vetterli, D.; Egelhof, P.; Henneck, R.; Jaskòla, M.; Mühry, H.; Sick, I.

    In order to extract the effect of vacuum polarization from 12C- 12C elastic scattering data, a detailed theoretical study of the low-energy Mott cross section is performed. It is shown that the contributions of nuclear interaction, Coulomb excitation, bremsstrahlung can be neglected, while radiative corrections and nuclear polarizability can be described by a small additional potential. Screening by atomic electrons is corrected by a screening function, which acts on all potentials. Relativistic effects are accounted for using the "Todorov equation". In order to overcome numerical difficulties for very long range potentials a WKB approximation and a semiquantal approach are discussed and compared. The study shows that the first-order vacuum-polarization potential contributes most to the correction of the cross section. All other contributions are at least one order of magnitude smaller.

  5. Kaon-nucleus scattering

    NASA Technical Reports Server (NTRS)

    Hong, Byungsik; Maung, Khin Maung; Wilson, John W.; Buck, Warren W.

    1989-01-01

    The derivations of the Lippmann-Schwinger equation and Watson multiple scattering are given. A simple optical potential is found to be the first term of that series. The number density distribution models of the nucleus, harmonic well, and Woods-Saxon are used without t-matrix taken from the scattering experiments. The parameterized two-body inputs, which are kaon-nucleon total cross sections, elastic slope parameters, and the ratio of the real to the imaginary part of the forward elastic scattering amplitude, are presented. The eikonal approximation was chosen as our solution method to estimate the total and absorptive cross sections for the kaon-nucleus scattering.

  6. The electronic structure of the Mott insulator VO2: the strongly correlated metal state is screened by impurity band

    NASA Astrophysics Data System (ADS)

    Kim, Hyun-Tak

    A Mott insulator VO2 (3d1) has a direct gap (Δdirect ~Vdirect) of 0.6 eV and an indirect gap of Δact ~Vdirect ~ 0.15 eV coming from impurity indirect band. At Tc, Δdirect =Δact = O is satisfied and the insulator-to-metal transition (IMT) occurs. The metallic carriers near core region can be trapped when a critical onsite Coulomb Uc exists. Then, a potential energy is defined as Vg =Vdirect +Uc +Vindirect = - (2 2 3) EF (1 + e (NtotNtotntot) (1 - exp (-Δact-ΔactkB T))) +Uc kB T))) +Uc ntot) (1 - exp (-Δact-ΔactkB T))) +Uc kB T))) +Uc 3) EF (1 + e (NtotNtotntot) (1 - exp (-Δact-ΔactkB T))) +Uc kB T))) +Uc ntot) (1 - exp (-Δact-ΔactkB T))) +Uc kB T))) +Uc , where Vdirect = - (2 2 3 3) EF is the screened Coulomb pseudopotential at K = 0. Δρ =NtotNtotntot ~ 0 . 018 % ntot ~ 0 . 018 % [1] is defined as the critical doping quantity, where ntot is the carrier density in the direct band and Ntot is the carrier density in the impurity band. In Uc < (2

  7. Orbitally driven trimerization in LiVO2 and LiVS2: a ``partial Mott transition''

    NASA Astrophysics Data System (ADS)

    Wu, Hua; Khomskii, D. I.

    2011-03-01

    Layered triangular-lattice transition-metal compounds often display interesting magnetic and electronic properties. Here we studied the formation of the trimerized spin-singlet state of the V3+ (S = 1) in vanadates Li VO2 and Li VS2 and their electronic structure with a special orbital order, using constrained LSDA+ U calculations combined with lattice optimization. The obtained results show that the trimerization distortion in Li VO2 increases as the effective U decreases, and the calculated distortion of ~ 0.3 AA at the small U = 1 eV agrees well with the experiments, indicating that Li VO2 is close to a metal-insulator transition. The corresponding distortion in Li VS2 is even stronger, being ~ 0.4 AA at the U = 1 eV, which is due to enhanced electron delocalization via increased V-S covalency, in spite of a lattice expansion. This agrees with the experimental finding that Li VS2 has a metal-insulator transition. The calculated energy gain associated with the trimerization well accounts for the observed structural phase transition temperature in Li VO2 and Li VS2 . We conclude that the trimerization in Li VO2 and Li VS2 is due to a partial delocalization of the orbitally ordered electrons---a ``partial Mott transition,'' occurring not in the whole system but in small clusters (here in trimers). This situation is contrasted with that in Na VO2 , which is further away from the localized-itinerant crossover and thus remains insulating with different orbital ordering.

  8. Limitations in scatter propagation

    NASA Astrophysics Data System (ADS)

    Lampert, E. W.

    1982-04-01

    A short description of the main scatter propagation mechanisms is presented; troposcatter, meteor burst communication and chaff scatter. For these propagation modes, in particular for troposcatter, the important specific limitations discussed are: link budget and resulting hardware consequences, diversity, mobility, information transfer and intermodulation and intersymbol interference, frequency range and future extension in frequency range for troposcatter, and compatibility with other services (EMC).

  9. Aureolegraph internal scattering correction.

    PubMed

    DeVore, John; Villanucci, Dennis; LePage, Andrew

    2012-11-20

    Two methods of determining instrumental scattering for correcting aureolegraph measurements of particulate solar scattering are presented. One involves subtracting measurements made with and without an external occluding ball and the other is a modification of the Langley Plot method and involves extrapolating aureolegraph measurements collected through a large range of solar zenith angles. Examples of internal scattering correction determinations using the latter method show similar power-law dependencies on scattering, but vary by roughly a factor of 8 and suggest that changing aerosol conditions during the determinations render this method problematic. Examples of corrections of scattering profiles using the former method are presented for a range of atmospheric particulate layers from aerosols to cumulus and cirrus clouds.

  10. Aureolegraph internal scattering correction.

    PubMed

    DeVore, John; Villanucci, Dennis; LePage, Andrew

    2012-11-20

    Two methods of determining instrumental scattering for correcting aureolegraph measurements of particulate solar scattering are presented. One involves subtracting measurements made with and without an external occluding ball and the other is a modification of the Langley Plot method and involves extrapolating aureolegraph measurements collected through a large range of solar zenith angles. Examples of internal scattering correction determinations using the latter method show similar power-law dependencies on scattering, but vary by roughly a factor of 8 and suggest that changing aerosol conditions during the determinations render this method problematic. Examples of corrections of scattering profiles using the former method are presented for a range of atmospheric particulate layers from aerosols to cumulus and cirrus clouds. PMID:23207299

  11. Scattering theory of nonlinear thermoelectricity in quantum coherent conductors.

    PubMed

    Meair, Jonathan; Jacquod, Philippe

    2013-02-27

    We construct a scattering theory of weakly nonlinear thermoelectric transport through sub-micron scale conductors. The theory incorporates the leading nonlinear contributions in temperature and voltage biases to the charge and heat currents. Because of the finite capacitances of sub-micron scale conducting circuits, fundamental conservation laws such as gauge invariance and current conservation require special care to be preserved. We do this by extending the approach of Christen and Büttiker (1996 Europhys. Lett. 35 523) to coupled charge and heat transport. In this way we write relations connecting nonlinear transport coefficients in a manner similar to Mott's relation between the linear thermopower and the linear conductance. We derive sum rules that nonlinear transport coefficients must satisfy to preserve gauge invariance and current conservation. We illustrate our theory by calculating the efficiency of heat engines and the coefficient of performance of thermoelectric refrigerators based on quantum point contacts and resonant tunneling barriers. We identify, in particular, rectification effects that increase device performance. PMID:23343784

  12. Direct probe of Mott-Hubbard to charge-transfer insulator transition and electronic structure evolution in transition-metal systems

    SciTech Connect

    Olalde-Velasco, P; Jimenez-Mier, J; Denlinger, JD; Hussain, Z; Yang, WL

    2011-07-11

    We report the most direct experimental verification of Mott-Hubbard and charge-transfer insulators through x-ray emission spectroscopy in transition-metal (TM) fluorides. The p-d hybridization features in the spectra allow a straightforward energy alignment of the anion-2p and metal-3d valence states, which visually shows the difference between the two types of insulators. Furthermore, in parallel with the theoretical Zaanen-Sawatzky-Allen diagram, a complete experimental systematics of the 3d Coulomb interaction and the 2p-3d charge-transfer energy is reported and could serve as a universal experimental trend for other TM systems including oxides.

  13. The role of Mott-Schottky heterojunctions in Ag-Ag8SnS6 as counter electrodes in dye-sensitized solar cells.

    PubMed

    He, Qingquan; Huang, Shoushuang; Wang, Cheng; Qiao, Qiquan; Liang, Na; Xu, Miao; Chen, Wenlong; Zai, Jiantao; Qian, Xuefeng

    2015-03-01

    Well-defined uniform pyramidal Ag-Ag8SnS6 heterodimers are prepared via a one-pot method. A plausible formation mechanism for the unique structures based on a seed-growth process and an etching effect due to oleylamine is proposed. The formed metal-semiconductor Mott-Schottky heterojunction promotes electron transfer from semiconducting Ag8 SnS6 to metallic Ag, which catalyzes the reduction of I3 (-) to I(-). When used as counter electrode in dye-sensitized solar cells, the heterodimers show comparable performance to platinum.

  14. Calculates Thermal Neutron Scattering Kernel.

    1989-11-10

    Version 00 THRUSH computes the thermal neutron scattering kernel by the phonon expansion method for both coherent and incoherent scattering processes. The calculation of the coherent part is suitable only for calculating the scattering kernel for heavy water.

  15. Kaon-nucleus scattering

    NASA Technical Reports Server (NTRS)

    Hong, Byungsik; Buck, Warren W.; Maung, Khin M.

    1989-01-01

    Two kinds of number density distributions of the nucleus, harmonic well and Woods-Saxon models, are used with the t-matrix that is taken from the scattering experiments to find a simple optical potential. The parameterized two body inputs, which are kaon-nucleon total cross sections, elastic slope parameters, and the ratio of the real to imaginary part of the forward elastic scattering amplitude, are shown. The eikonal approximation was chosen as the solution method to estimate the total and absorptive cross sections for the kaon-nucleus scattering.

  16. Light scattering and dissipative dynamics of many fermionic atoms in an optical lattice

    NASA Astrophysics Data System (ADS)

    Sarkar, S.; Langer, S.; Schachenmayer, J.; Daley, A. J.

    2014-08-01

    We investigate the many-body dissipative dynamics of fermionic atoms in an optical lattice in the presence of incoherent light scattering. Deriving and solving a master equation to describe this process microscopically for many particles, we observe contrasting behavior in terms of the robustness against this type of heating for different many-body states. In particular, we find that the magnetic correlations exhibited by a two-component gas in the Mott insulating phase should be particularly robust against decoherence from light scattering, because the decoherence in the lowest band is suppressed by a larger factor than the time scales for effective superexchange interactions that drive coherent dynamics. Furthermore, the derived formalism naturally generalizes to analogous states with SU(N) symmetry. In contrast, for typical atomic and laser parameters, two-particle correlation functions describing bound dimers for strong attractive interactions exhibit superradiant effects due to the indistinguishability of off-resonant photons scattered by atoms in different internal states. This leads to rapid decay of correlations describing off-diagonal long-range order for these states. Our predictions should be directly measurable in ongoing experiments, providing a basis for characterizing and controlling heating processes in quantum simulation with fermions.

  17. Cosmic Ray Scattering Radiography

    NASA Astrophysics Data System (ADS)

    Morris, C. L.

    2015-12-01

    Cosmic ray muons are ubiquitous, are highly penetrating, and can be used to measure material densities by either measuring the stopping rate or by measuring the scattering of transmitted muons. The Los Alamos team has studied scattering radiography for a number of applications. Some results will be shown of scattering imaging for a range of practical applications, and estimates will be made of the utility of scattering radiography for nondestructive assessments of large structures and for geological surveying. Results of imaging the core of the Toshiba Nuclear Critical Assembly (NCA) Reactor in Kawasaki, Japan and simulations of imaging the damaged cores of the Fukushima nuclear reactors will be presented. Below is an image made using muons of a core configuration for the NCA reactor.

  18. Intra-beam scattering

    NASA Astrophysics Data System (ADS)

    Piwinski, A.

    Intra-beam scattering is analysed and the rise times or damping times of the beam dimensions are derived. The theoretical results are compared with experimental values obtained on the CERN AA and SPS machines.

  19. Environment scattering in GADRAS.

    SciTech Connect

    Thoreson, Gregory G.; Mitchell, Dean J; Theisen, Lisa Anne; Harding, Lee T.

    2013-09-01

    Radiation transport calculations were performed to compute the angular tallies for scattered gamma-rays as a function of distance, height, and environment. Greens Functions were then used to encapsulate the results a reusable transformation function. The calculations represent the transport of photons throughout scattering surfaces that surround sources and detectors, such as the ground and walls. Utilization of these calculations in GADRAS (Gamma Detector Response and Analysis Software) enables accurate computation of environmental scattering for a variety of environments and source configurations. This capability, which agrees well with numerous experimental benchmark measurements, is now deployed with GADRAS Version 18.2 as the basis for the computation of scattered radiation.

  20. Rayleigh Scattering Diagnostics Workshop

    NASA Technical Reports Server (NTRS)

    Seasholtz, Richard (Compiler)

    1996-01-01

    The Rayleigh Scattering Diagnostics Workshop was held July 25-26, 1995 at the NASA Lewis Research Center in Cleveland, Ohio. The purpose of the workshop was to foster timely exchange of information and expertise acquired by researchers and users of laser based Rayleigh scattering diagnostics for aerospace flow facilities and other applications. This Conference Publication includes the 12 technical presentations and transcriptions of the two panel discussions. The first panel was made up of 'users' of optical diagnostics, mainly in aerospace test facilities, and its purpose was to assess areas of potential applications of Rayleigh scattering diagnostics. The second panel was made up of active researchers in Rayleigh scattering diagnostics, and its purpose was to discuss the direction of future work.

  1. CONTINUOUS ROTATION SCATTERING CHAMBER

    DOEpatents

    Verba, J.W.; Hawrylak, R.A.

    1963-08-01

    An evacuated scattering chamber for use in observing nuclear reaction products produced therein over a wide range of scattering angles from an incoming horizontal beam that bombards a target in the chamber is described. A helically moving member that couples the chamber to a detector permits a rapid and broad change of observation angles without breaching the vacuum in the chamber. Also, small inlet and outlet openings are provided whose size remains substantially constant. (auth)

  2. Positron-rubidium scattering

    NASA Technical Reports Server (NTRS)

    Mceachran, R. P.; Horbatsch, M.; Stauffer, A. D.

    1990-01-01

    A 5-state close-coupling calculation (5s-5p-4d-6s-6p) was carried out for positron-Rb scattering in the energy range 3.7 to 28.0 eV. In contrast to the results of similar close-coupling calculations for positron-Na and positron-K scattering the (effective) total integrated cross section has an energy dependence which is contrary to recent experimental measurements.

  3. Mott behavior of ultrathin epitaxial LaNiO3 films and interfaces via hard x-ray and standing-wave excited photoemission

    NASA Astrophysics Data System (ADS)

    Gray, Alexander; Kaiser, Alexander; Son, Junwoo; Janotti, Anderson; Yang, See-Hun; Bostwick, Aaron; Ueda, Shigenori; Kobayashi, Keisuke; van de Walle, Chris; Stemmer, Susanne; Fadley, Charles

    2012-02-01

    In this study we apply several emerging x-ray photoemission techniques to study Mott behavior of ultrathin LaNiO3 films and interfaces in a depth-resolved manner. In order to understand the effects of thickness and strain on the electronic structure, we apply hard x-ray photoemission (HAXPES) at 6 keV to epitaxial LaNiO3 films of varying thickness under compressive and tensile strain. Mott metal-to-insulator transition is observed for the thinnest films. Furthermore, standing-wave-excited photoemission is used to study the electronic structure of ultrathin LaNiO3 in a SrTiO3/LaNiO3 superlattice. Standing-wave measurements of core-level and valence band spectra are used to derive layer-resolved densities of states, revealing a suppression of electronic states near the Fermi level in the multilayer as compared to bulk LaNiO3. Further analysis shows that the suppression of these states is not homogeneously distributed over the LaNiO3 layers but is more pronounced near the interfaces.

  4. Size and symmetry of the superconducting gap in the f.c.c. Cs3C60 polymorph close to the metal-Mott insulator boundary

    PubMed Central

    Potočnik, Anton; Krajnc, Andraž; Jeglič, Peter; Takabayashi, Yasuhiro; Ganin, Alexey Y.; Prassides, Kosmas; Rosseinsky, Matthew J.; Arčon, Denis

    2014-01-01

    The alkali fullerides, A3C60 (A = alkali metal) are molecular superconductors that undergo a transition to a magnetic Mott-insulating state at large lattice parameters. However, although the size and the symmetry of the superconducting gap, Δ, are both crucial for the understanding of the pairing mechanism, they are currently unknown for superconducting fullerides close to the correlation-driven magnetic insulator. Here we report a comprehensive nuclear magnetic resonance (NMR) study of face-centred-cubic (f.c.c.) Cs3C60 polymorph, which can be tuned continuously through the bandwidth-controlled Mott insulator-metal/superconductor transition by pressure. When superconductivity emerges from the insulating state at large interfullerene separations upon compression, we observe an isotropic (s-wave) Δ with a large gap-to-superconducting transition temperature ratio, 2Δ0/kBTc = 5.3(2) [Δ0 = Δ(0 K)]. 2Δ0/kBTc decreases continuously upon pressurization until it approaches a value of ~3.5, characteristic of weak-coupling BCS theory of superconductivity despite the dome-shaped dependence of Tc on interfullerene separation. The results indicate the importance of the electronic correlations for the pairing interaction as the metal/superconductor-insulator boundary is approached. PMID:24584087

  5. Spin-orbit coupling, strong correlation, and insulator-metal transitions: The Jeff=3/2 ferromagnetic Dirac-Mott insulator Ba2NaOsO6

    NASA Astrophysics Data System (ADS)

    Gangopadhyay, Shruba; Pickett, Warren E.

    2015-01-01

    The double perovskite Ba2NaOsO6 (BNOO), an exotic example of a very high oxidation state (heptavalent) osmium d1 compound and also uncommon by being a ferromagnetic open d -shell (Mott) insulator without Jahn-Teller (JT) distortion, is modeled using a density functional theory based hybrid functional incorporating exact exchange for correlated electronic orbitals and including the large spin-orbit coupling (SOC). The experimentally observed narrow-gap ferromagnetic insulating ground state is obtained, but only when including spin-orbit coupling, making this a Dirac-Mott insulator. The calculated easy axis along [110] is in accord with experiment, providing additional support that this approach provides a realistic method for studying this system. The predicted spin density for [110] spin orientation is nearly cubic (unlike for other directions), providing an explanation for the absence of JT distortion. An orbital moment of -0.4 μB strongly compensates the +0.5 μB spin moment on Os, leaving a strongly compensated moment more in line with experiment. Remarkably, the net moment lies primarily on the oxygen ions. An insulator-metal transition, by rotating the magnetization direction with an external field under moderate pressure, is predicted as one consequence of strong SOC, and metallization under moderate pressure is predicted. Comparison is made with the isostructural, isovalent insulator Ba2LiOsO6 , which, however, orders antiferromagnetically.

  6. A new route to the Mott-Hubbard metal-insulator transition: Strong correlations effects in Pr0.7Ca0.3MnO3

    PubMed Central

    Lee, Hong Sub; Choi, Sun Gyu; Park, Hyung-Ho; Rozenberg, M. J.

    2013-01-01

    Resistive random access memory based on the resistive switching phenomenon is emerging as a strong candidate for next generation non-volatile memory. So far, the resistive switching effect has been observed in many transition metal oxides, including strongly correlated ones, such as, cuprate superconductors, colossal magnetoresistant manganites and Mott insulators. However, up to now, no clear evidence of the possible relevance of strong correlation effects in the mechanism of resistive switching has been reported. Here, we study Pr0.7Ca0.3MnO3, which shows bipolar resistive switching. Performing micro-spectroscopic studies on its bare surface we are able to track the systematic electronic structure changes in both, the low and high resistance state. We find that a large change in the electronic conductance is due to field-induced oxygen vacancies, which drives a Mott metal-insulator transition at the surface. Our study demonstrates that strong correlation effects may be incorporated to the realm of the emerging oxide electronics.

  7. Elastic scattering of hadrons

    NASA Astrophysics Data System (ADS)

    Dremin, I. M.

    2013-01-01

    Colliding high-energy hadrons either produce new particles or scatter elastically with their quantum numbers conserved and no other particles produced. We consider the latter case here. Although inelastic processes dominate at high energies, elastic scattering contributes considerably (18-25%) to the total cross section. Its share first decreases and then increases at higher energies. Small-angle scattering prevails at all energies. Some characteristic features can be seen that provide information on the geometrical structure of the colliding particles and the relevant dynamical mechanisms. The steep Gaussian peak at small angles is followed by the exponential (Orear) regime with some shoulders and dips, and then by a power-law decrease. Results from various theoretical approaches are compared with experimental data. Phenomenological models claiming to describe this process are reviewed. The unitarity condition predicts an exponential fall for the differential cross section with an additional substructure to occur exactly between the low momentum transfer diffraction cone and a power-law, hard parton scattering regime under high momentum transfer. Data on the interference of the Coulomb and nuclear parts of amplitudes at extremely small angles provide the value of the real part of the forward scattering amplitude. The real part of the elastic scattering amplitude and the contribution of inelastic processes to the imaginary part of this amplitude (the so-called overlap function) are also discussed. Problems related to the scaling behavior of the differential cross section are considered. The power-law regime at highest momentum transfer is briefly described.

  8. Laser light scattering review

    NASA Astrophysics Data System (ADS)

    Schaetzel, Klaus

    1989-08-01

    Since the development of laser light sources and fast digital electronics for signal processing, the classical discipline of light scattering on liquid systems experienced a strong revival plus an enormous expansion, mainly due to new dynamic light scattering techniques. While a large number of liquid systems can be investigated, ranging from pure liquids to multicomponent microemulsions, this review is largely restricted to applications on Brownian particles, typically in the submicron range. Static light scattering, the careful recording of the angular dependence of scattered light, is a valuable tool for the analysis of particle size and shape, or of their spatial ordering due to mutual interactions. Dynamic techniques, most notably photon correlation spectroscopy, give direct access to particle motion. This may be Brownian motion, which allows the determination of particle size, or some collective motion, e.g., electrophoresis, which yields particle mobility data. Suitable optical systems as well as the necessary data processing schemes are presented in some detail. Special attention is devoted to topics of current interest, like correlation over very large lag time ranges or multiple scattering.

  9. Laser light scattering review

    NASA Technical Reports Server (NTRS)

    Schaetzel, Klaus

    1989-01-01

    Since the development of laser light sources and fast digital electronics for signal processing, the classical discipline of light scattering on liquid systems experienced a strong revival plus an enormous expansion, mainly due to new dynamic light scattering techniques. While a large number of liquid systems can be investigated, ranging from pure liquids to multicomponent microemulsions, this review is largely restricted to applications on Brownian particles, typically in the submicron range. Static light scattering, the careful recording of the angular dependence of scattered light, is a valuable tool for the analysis of particle size and shape, or of their spatial ordering due to mutual interactions. Dynamic techniques, most notably photon correlation spectroscopy, give direct access to particle motion. This may be Brownian motion, which allows the determination of particle size, or some collective motion, e.g., electrophoresis, which yields particle mobility data. Suitable optical systems as well as the necessary data processing schemes are presented in some detail. Special attention is devoted to topics of current interest, like correlation over very large lag time ranges or multiple scattering.

  10. Sudden slowing down of charge carrier dynamics at the Mott metal-insulator transition in kappa-(D{sub 8}-BEDT-TTF){sub 2}Cu[N(CN){sub 2}]Br.

    SciTech Connect

    Brandenburg, J.; Muller, J.; Schlueter, J. A.

    2012-02-01

    We investigate the dynamics of correlated charge carriers in the vicinity of the Mott metal-insulator (MI) transition in the quasi-two-dimensional organic charge-transfer salt {kappa}-(D{sub 8}-BEDT-TTF){sub 2}Cu[N(CN){sub 2}]Br by means of fluctuation (noise) spectroscopy. The observed 1/f-type fluctuations are quantitatively very well described by a phenomenological model based on the concept of non-exponential kinetics. The main result is a correlation-induced enhancement of the fluctuations accompanied by a substantial shift of spectral weight to low frequencies in the vicinity of the Mott critical endpoint. This sudden slowing down of the electron dynamics, observed here in a pure Mott system, may be a universal feature of MI transitions. Our findings are compatible with an electronic phase separation in the critical region of the phase diagram and offer an explanation for the not yet understood absence of effective mass enhancement when crossing the Mott transition.

  11. Electromagnetic scattering theory

    NASA Technical Reports Server (NTRS)

    Bird, J. F.; Farrell, R. A.

    1986-01-01

    Electromagnetic scattering theory is discussed with emphasis on the general stochastic variational principle (SVP) and its applications. The stochastic version of the Schwinger-type variational principle is presented, and explicit expressions for its integrals are considered. Results are summarized for scalar wave scattering from a classic rough-surface model and for vector wave scattering from a random dielectric-body model. Also considered are the selection of trial functions and the variational improvement of the Kirchhoff short-wave approximation appropriate to large size-parameters. Other applications of vector field theory discussed include a general vision theory and the analysis of hydromagnetism induced by ocean motion across the geomagnetic field. Levitational force-torque in the magnetic suspension of the disturbance compensation system (DISCOS), now deployed in NOVA satellites, is also analyzed using the developed theory.

  12. MAGNETIC NEUTRON SCATTERING

    SciTech Connect

    ZALIZNYAK,I.A.; LEE,S.H.

    2004-07-30

    Much of our understanding of the atomic-scale magnetic structure and the dynamical properties of solids and liquids was gained from neutron-scattering studies. Elastic and inelastic neutron spectroscopy provided physicists with an unprecedented, detailed access to spin structures, magnetic-excitation spectra, soft-modes and critical dynamics at magnetic-phase transitions, which is unrivaled by other experimental techniques. Because the neutron has no electric charge, it is an ideal weakly interacting and highly penetrating probe of matter's inner structure and dynamics. Unlike techniques using photon electric fields or charged particles (e.g., electrons, muons) that significantly modify the local electronic environment, neutron spectroscopy allows determination of a material's intrinsic, unperturbed physical properties. The method is not sensitive to extraneous charges, electric fields, and the imperfection of surface layers. Because the neutron is a highly penetrating and non-destructive probe, neutron spectroscopy can probe the microscopic properties of bulk materials (not just their surface layers) and study samples embedded in complex environments, such as cryostats, magnets, and pressure cells, which are essential for understanding the physical origins of magnetic phenomena. Neutron scattering is arguably the most powerful and versatile experimental tool for studying the microscopic properties of the magnetic materials. The magnitude of the cross-section of the neutron magnetic scattering is similar to the cross-section of nuclear scattering by short-range nuclear forces, and is large enough to provide measurable scattering by the ordered magnetic structures and electron spin fluctuations. In the half-a-century or so that has passed since neutron beams with sufficient intensity for scattering applications became available with the advent of the nuclear reactors, they have became indispensable tools for studying a variety of important areas of modern science

  13. Interstellar Dust Scattering Properties

    NASA Astrophysics Data System (ADS)

    Gordon, K. D.

    2004-05-01

    Studies of dust scattering properties in astrophysical objects with Milky Way interstellar dust are reviewed. Such objects are reflection nebulae, dark clouds, and the Diffuse Galactic Light (DGL). To ensure their basic quality, studies had to satisfy four basic criteria to be included in this review. These four criteria significantly reduced the scatter in dust properties measurements, especially in the case of the DGL. Determinations of dust scattering properties were found to be internally consistent for each object type as well as consistent between object types. The 2175 Å bump is seen as an absorption feature. Comparisons with dust grain models find general agreement with significant disagreements at particular wavelengths (especially in the far-ultraviolet). Finally, unanswered questions and future directions are enumerated.

  14. Dynamic Scattering Mode LCDs

    NASA Astrophysics Data System (ADS)

    Bahadur, Birendra

    The following sections are included: * INTRODUCTION * CELL DESIGNING * EXPERIMENTAL OBSERVATIONS IN NEMATICS RELATED WITH DYNAMIC SCATTERING * Experimental Observations at D.C. Field and Electrode Effects * Experimental Observation at Low Frequency A.C. Fields * Homogeneously Aligned Nematic Regime * Williams Domains * Dynamic Scattering * Experimental Observation at High Frequency A.C. Field * Other Experimental Observations * THEORETICAL INTERPRETATIONS * Felici Model * Carr-Helfrich Model * D.C. Excitation * Dubois-Violette, de Gennes and Parodi Model * Low Freqency or Conductive Regime * High Frequency or Dielectric Regime * DYNAMIC SCATTERING IN SMECRIC A PHASE * ELECTRO-OPTICAL CHARACTERISTICS AND LIMITATIONS * Contrast Ratio vs. Voltage, Viewing Angle, Cell Gap, Wavelength and Temperature * Display Current vs. Voltage, Cell Gap and Temperature * Switching Time * Effect of Alignment * Effect of Conductivity, Temperature and Frequency * Addressing of DSM LCDs * Limitations of DSM LCDs * ACKNOWLEDGEMENTS * REFERENCES

  15. Scattering Of Light Nuclei

    SciTech Connect

    Quaglioni, S; Navratil, P; Roth, R

    2009-12-15

    The exact treatment of nuclei starting from the constituent nucleons and the fundamental interactions among them has been a long-standing goal in nuclear physics. Above all nuclear scattering and reactions, which require the solution of the many-body quantum-mechanical problem in the continuum, represent an extraordinary theoretical as well as computational challenge for ab initio approaches.We present a new ab initio many-body approach which derives from the combination of the ab initio no-core shell model with the resonating-group method [4]. By complementing a microscopic cluster technique with the use of realistic interactions, and a microscopic and consistent description of the nucleon clusters, this approach is capable of describing simultaneously both bound and scattering states in light nuclei. We will discuss applications to neutron and proton scattering on sand light p-shell nuclei using realistic nucleon-nucleon potentials, and outline the progress toward the treatment of more complex reactions.

  16. Spatially resolved scattering polarimeter.

    PubMed

    Kohlgraf-Owens, Thomas; Dogariu, Aristide

    2009-05-01

    We demonstrate a compact, spatially resolved polarimeter based on a coherent optical fiber bundle coupled with a thin layer of scattering centers. The use of scattering for polarization encoding allows the polarimeter to work across broad angular and spectral domains. Optical fiber bundles provide high spatial resolution of the incident field. Because neighboring elements of the bundle interact with the incident field differently, only a single interaction of the fiber bundle with the unknown field is needed to perform the measurement. Experimental results are shown to demonstrate the capability to perform imaging polarimetry. PMID:19412259

  17. Atom scattering from metals

    NASA Astrophysics Data System (ADS)

    Hayes, W. W.

    In the initial portion of this dissertation studies of Ar scattering from Ru(0001) at thermal and hyperthermal energies are compared to calculations with classical scattering theory. These data exhibited a number of characteristics that are unusual in comparison to other systems for which atomic beam experiments have been carried out under similar conditions. The measured energy losses were unusually small. Some of the angular distributions exhibited an anomalous shoulder feature in addition to a broad peak near the specular direction and quantum mechanical diffraction was observed under conditions for which it was not expected. Many of the unusual features observed in the measurements are explained, but only upon using an effective surface mass of 2.3 Ru atomic masses, which implies collective effects in the Ru crystal. The large effective mass, because it leads to substantially larger Debye-Waller factors, explains and confirms the observations of diffraction features. It also leads to the interesting conclusion that Ru is a metal for which atomic beam scattering measurements in the purely quantum mechanical regime, where diffraction and single-phonon creation are dominant, should be possible not only with He atoms, but with many other atomic species with larger masses. A useful theoretical expression for interpreting and analyzing observed scattering intensity spectra for atomic and molecular collisions with surfaces is the differential reflection coefficient for a smooth, vibrating surface. This differential reflection coefficient depends on a parameter, usually expressed in dimensions of velocity, that arises due to correlated motions of neighboring regions of the surface and can be evaluated if the polarization vectors of the phonons near the surface are known. As a part of this dissertation experimental conditions are suggested under which this velocity paramenter may be more precisely measured than it has been in the past. Experimental data for scattering

  18. Fluorescence and Light Scattering

    ERIC Educational Resources Information Center

    Clarke, Ronald J.; Oprysa, Anna

    2004-01-01

    The aim of the mentioned experiment is to aid students in developing tactics for distinguishing between signals originating from fluorescence and light scattering. Also, the experiment provides students with a deeper understanding of the physicochemical bases of each phenomenon and shows that the techniques are actually related.

  19. Nanowire electron scattering spectroscopy

    NASA Technical Reports Server (NTRS)

    Hunt, Brian D. (Inventor); Bronikowski, Michael (Inventor); Wong, Eric W. (Inventor); von Allmen, Paul (Inventor); Oyafuso, Fabiano A. (Inventor)

    2009-01-01

    Methods and devices for spectroscopic identification of molecules using nanoscale wires are disclosed. According to one of the methods, nanoscale wires are provided, electrons are injected into the nanoscale wire; and inelastic electron scattering is measured via excitation of low-lying vibrational energy levels of molecules bound to the nanoscale wire.

  20. Critical fluid light scattering

    NASA Technical Reports Server (NTRS)

    Gammon, Robert W.

    1988-01-01

    The objective is to measure the decay rates of critical density fluctuations in a simple fluid (xenon) very near its liquid-vapor critical point using laser light scattering and photon correlation spectroscopy. Such experiments were severely limited on Earth by the presence of gravity which causes large density gradients in the sample when the compressibility diverges approaching the critical point. The goal is to measure fluctuation decay rates at least two decades closer to the critical point than is possible on earth, with a resolution of 3 microK. This will require loading the sample to 0.1 percent of the critical density and taking data as close as 100 microK to the critical temperature. The minimum mission time of 100 hours will allow a complete range of temperature points to be covered, limited by the thermal response of the sample. Other technical problems have to be addressed such as multiple scattering and the effect of wetting layers. The experiment entails measurement of the scattering intensity fluctuation decay rate at two angles for each temperature and simultaneously recording the scattering intensities and sample turbidity (from the transmission). The analyzed intensity and turbidity data gives the correlation length at each temperature and locates the critical temperature. The fluctuation decay rate data from these measurements will provide a severe test of the generalized hydrodynamic theories of transport coefficients in the critical regions. When compared to equivalent data from binary liquid critical mixtures they will test the universality of critical dynamics.

  1. Inelastic Scattering Form Factors

    1992-01-01

    ATHENA-IV computes form factors for inelastic scattering calculations, using single-particle wave functions that are eigenstates of motion in either a Woods-Saxon potential well or a harmonic oscillator well. Two-body forces of Gauss, Coulomb, Yukawa, and a sum of cut-off Yukawa radial dependences are available.

  2. The happy marriage between electron-phonon superconductivity and Mott physics in Cs3C60: A first-principle phase diagram

    NASA Astrophysics Data System (ADS)

    Capone, Massimo; Nomura, Yusuke; Sakai, Shiro; Giovannetti, Gianluca; Arita, Ryotaro

    The phase diagram of doped fullerides like Cs3C60 as a function of the spacing between fullerene molecules is characterized by a first-order transition between a Mott insulator and an s-wave superconductor with a dome-shaped behavior of the critical temperature. By means of an ab-initio modeling of the bandstructure, the electron-phonon interaction and the interaction parameter and a Dynamical Mean-Field Theory solution, we reproduce the phase diagram and demonstrate that phonon superconductivity benefits from strong correlations confirming earlier model predictions. The role of correlations is manifest also in infrared measurements carried out by L. Baldassarre. The superconducting phase shares many similarities with ''exotic'' superconductors with electronic pairing, suggesting that the anomalies in the ''normal'' state, rather than the pairing glue, can be the real common element unifying a wide family of strongly correlated superconductors including cuprates and iron superconductors

  3. Pressure-induced electronic and magnetic phase transitions in a Mott insulator: Ti-doped C a3R u2O7 bilayer ruthenate

    NASA Astrophysics Data System (ADS)

    Zou, T.; Cao, H. B.; Liu, G. Q.; Peng, J.; Gottschalk, M.; Zhu, M.; Zhao, Y.; Leão, J. B.; Tian, W.; Mao, Z. Q.; Ke, X.

    2016-07-01

    We report the hydrostatic pressure-induced electronic and magnetic phase transitions in a Mott insulator, a bilayer ruthenate C a3(Ru0.97Ti0.03 ) 2O7 , via electronic transport and single crystal neutron diffraction measurements. The system undergoes an insulator-metal transition at a very small hydrostatic pressure ≈0.04 GPa, followed by a magnetic phase transition around 0.3 GPa, suggesting that the low energy charge fluctuation and magnetic ordering couple to the pressure separately in this compound. The a b initio calculations show that the suppressed Ru O6 flattening induced by the pressure reduces the orbital polarization and gives rise to an insulator-metal transition preceding the magnetic phase transition.

  4. Angle Resolved Photoemission Spectroscopy Studies of the Mott Insulator to Superconductor Evolution in Ca2-xNaxCuO2Cl2

    SciTech Connect

    Shen, Kyle Michael

    2005-09-02

    It is widely believed that many of the exotic physical properties of the high-T{sub c} cuprate superconductors arise from the proximity of these materials to the strongly correlated, antiferromagnetic Mott insulating state. Therefore, one of the fundamental questions in the field of high-temperature superconductivity is to understand the insulator-to-superconductor transition and precisely how the electronic structure of Mott insulator evolves as the first holes are doped into the system. This dissertation presents high-resolution, doping dependent angle-resolved photoemission (ARPES) studies of the cuprate superconductor Ca{sub 2-x}Na{sub x}CuO{sub 2}Cl{sub 2}, spanning from the undoped parent Mott insulator to a high-temperature superconductor with a T{sub c} of 22 K. A phenomenological model is proposed to explain how the spectral lineshape, the quasiparticle band dispersion, and the chemical potential all progress with doping in a logical and self-consistent framework. This model is based on Franck-Condon broadening observed in polaronic systems where strong electron-boson interactions cause the quasiparticle residue, Z, to be vanishingly small. Comparisons of the low-lying states to different electronic states in the valence band strongly suggest that the coupling of the photohole to the lattice (i.e. lattice polaron formation) is the dominant broadening mechanism for the lower Hubbard band states. Combining this polaronic framework with high-resolution ARPES measurements finally provides a resolution to the long-standing controversy over the behavior of the chemical potential in the high-T{sub c} cuprates. This scenario arises from replacing the conventional Fermi liquid quasiparticle interpretation of the features in the Mott insulator by a Franck-Condon model, allowing the reassignment of the position of the quasiparticle pole. As a function of hole doping, the chemical potential shifts smoothly into the valence band while spectral weight is transferred

  5. Strong lattice correlation of non-equilibrium quasiparticles in a pseudospin-1/2 Mott insulator Sr2IrO4

    DOE PAGESBeta

    Li, Yuelin; Schaller, Richard D.; Zhu, Mengze; Walko, Donald A.; Kim, Jungho; Ke, Xianglin; Miao, Ludi; Mao, Z. Q.

    2016-01-20

    In correlated oxides the coupling of quasiparticles to other degrees of freedom such as spin and lattice plays critical roles in the emergence of symmetry-breaking quantum ordered states such as high temperature superconductivity. We report a strong lattice coupling of photon-induced quasiparticles in spin-orbital coupling Mott insulator Sr2IrO4 probed via optical excitation. Combining time-resolved x-ray diffraction and optical spectroscopy techniques, we reconstruct a spatiotemporal map of the diffusion of these quasiparticles. Lastly, due to the unique electronic configuration of the quasiparticles, the strong lattice correlation is unexpected but extends the similarity between Sr2IrO4 and cuprates to a new dimension ofmore » electron-phonon coupling which persists under highly non-equilibrium conditions.« less

  6. Strong lattice correlation of non-equilibrium quasiparticles in a pseudospin-1/2 Mott insulator Sr2IrO4

    PubMed Central

    Li, Yuelin; Schaller, Richard D.; Zhu, Mengze; Walko, Donald A.; Kim, Jungho; Ke, Xianglin; Miao, Ludi; Mao, Z. Q.

    2016-01-01

    In correlated oxides the coupling of quasiparticles to other degrees of freedom such as spin and lattice plays critical roles in the emergence of symmetry-breaking quantum ordered states such as high temperature superconductivity. We report a strong lattice coupling of photon-induced quasiparticles in spin-orbital coupling Mott insulator Sr2IrO4 probed via optical excitation. Combining time-resolved x-ray diffraction and optical spectroscopy techniques, we reconstruct a spatiotemporal map of the diffusion of these quasiparticles. Due to the unique electronic configuration of the quasiparticles, the strong lattice correlation is unexpected but extends the similarity between Sr2IrO4 and cuprates to a new dimension of electron-phonon coupling which persists under highly non-equilibrium conditions. PMID:26787094

  7. Scaling Theory of the Mott Transition and Breakdown of the Gr"uneisen Scaling Near a Finite-Temperature Critical End Point

    NASA Astrophysics Data System (ADS)

    Bartosch, Lorenz

    2012-02-01

    We discuss a scaling theory of the lattice response in the vicinity of a finite-temperature critical end point. The thermal expansivity is shown to be more singular than the specific heat such that the Gr"uneisen ratio diverges as the critical point is approached, except for its immediate vicinity. More generally, we express the thermal expansivity in terms of a scaling function which we explicitly evaluate for the two-dimensional Ising universality class. Recent thermal expansivity measurements on the layered organic conductor κ-(BEDT-TTF)2X close to the Mott transition are well described by our theory.[2mm] [1] Lorenz Bartosch, Mariano de Souza, and Michael Lang, Physical Review Letters 104, 245701 (2010).

  8. Magnetic-field induced crossover of superconducting percolation regimes in the layered organic Mott system {kappa}-(BEDT-TTF){sub 2}Cu[N(CN){sub 2}]Cl.

    SciTech Connect

    Mueller, J.; Brandenberg, J.; Schlueter, J. A.; Materials Science Division; Max Planck Inst. for Chemical Physics of Solids

    2009-01-01

    Fluctuation spectroscopy is used to investigate the organic bandwidth-controlled Mott system {kappa}-(BEDT-TTF){sub 2}Cu[N(CN){sub 2}]Cl. We find evidence for percolative-type superconductivity in the spatially inhomogeneous coexistence region of antiferromagnetic insulating and superconducting states. When the superconducting transition is driven by a magnetic field, percolation seems to be dominated by instable superconducting clusters upon approaching T{sub c}(B) from above, before a 'classical' type of percolation is resumed at low fields, dominated by the fractional change of superconducting clusters. The 1/f noise is resolved into Lorentzian spectra in the crossover region, where the action of an individual fluctuator is enhanced, pointing to a mesoscopic phase separation.

  9. Small angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Cousin, Fabrice

    2015-10-01

    Small Angle Neutron Scattering (SANS) is a technique that enables to probe the 3-D structure of materials on a typical size range lying from ˜ 1 nm up to ˜ a few 100 nm, the obtained information being statistically averaged on a sample whose volume is ˜ 1 cm3. This very rich technique enables to make a full structural characterization of a given object of nanometric dimensions (radius of gyration, shape, volume or mass, fractal dimension, specific area…) through the determination of the form factor as well as the determination of the way objects are organized within in a continuous media, and therefore to describe interactions between them, through the determination of the structure factor. The specific properties of neutrons (possibility of tuning the scattering intensity by using the isotopic substitution, sensitivity to magnetism, negligible absorption, low energy of the incident neutrons) make it particularly interesting in the fields of soft matter, biophysics, magnetic materials and metallurgy. In particular, the contrast variation methods allow to extract some informations that cannot be obtained by any other experimental techniques. This course is divided in two parts. The first one is devoted to the description of the principle of SANS: basics (formalism, coherent scattering/incoherent scattering, notion of elementary scatterer), form factor analysis (I(q→0), Guinier regime, intermediate regime, Porod regime, polydisperse system), structure factor analysis (2nd Virial coefficient, integral equations, characterization of aggregates), and contrast variation methods (how to create contrast in an homogeneous system, matching in ternary systems, extrapolation to zero concentration, Zero Averaged Contrast). It is illustrated by some representative examples. The second one describes the experimental aspects of SANS to guide user in its future experiments: description of SANS spectrometer, resolution of the spectrometer, optimization of spectrometer

  10. Rayleigh's Scattering Revised

    NASA Astrophysics Data System (ADS)

    Kolomiets, Sergey; Gorelik, Andrey

    This report is devoted to a discussion of applicability limits of Rayleigh’s scattering model. Implicitly, Rayleigh’s ideas are being used in a wide range of remote sensing applications. To begin with it must be noted that most techniques which have been developed to date for measurements by means of active instruments for remote sensing in case of the target is a set of distributed moving scatters are only hopes, to say so, on measurements per se. The problem is that almost all of such techniques use a priori information about the microstructure of the object of interest during whole measurement session. As one can find in the literature, this approach may happily be applied to systems with identical particles. However, it is not the case with respect to scattering targets that consist of particles of different kind or having a particle size distribution. It must be especially noted that the microstructure of most of such targets changes significantly with time and/or space. Therefore, the true measurement techniques designed to be applicable in such conditions must be not only adaptable in order to take into account a variety of models of an echo interpretation, but also have a well-developed set of clear-cut criteria of applicability and exact means of accuracy estimation. So such techniques will require much more parameters to be measured. In spite of the fact that there is still room for some improvements within classical models and approaches, it is multiwavelength approach that may be seen as the most promising way of development towards obtaining an adequate set of the measured parameters required for true measurement techniques. At the same time, Rayleigh’s scattering is an invariant in regard to a change of the wavelength as it follows from the point of view dominating nowadays. In the light of such an idea, the synergy between multivawelength measurements may be achieved - to a certain extent - by means of the synchronous usage of Rayleigh’s and

  11. Stochastic methods for light propagation and recurrent scattering in saturated and nonsaturated atomic ensembles

    NASA Astrophysics Data System (ADS)

    Lee, Mark D.; Jenkins, Stewart D.; Ruostekoski, Janne

    2016-06-01

    We derive equations for the strongly coupled system of light and dense atomic ensembles. The formalism includes an arbitrary internal-level structure for the atoms and is not restricted to weak excitation of atoms by light. In the low-light-intensity limit for atoms with a single electronic ground state, the full quantum field-theoretical representation of the model can be solved exactly by means of classical stochastic electrodynamics simulations for stationary atoms that represent cold atomic ensembles. Simulations for the optical response of atoms in a quantum degenerate regime require one to synthesize a stochastic ensemble of atomic positions that generates the corresponding quantum statistical position correlations between the atoms. In the case of multiple ground levels or at light intensities where saturation becomes important, the classical simulations require approximations that neglect quantum fluctuations between the levels. We show how the model is extended to incorporate corrections due to quantum fluctuations that result from virtual scattering processes. In the low-light-intensity limit, we illustrate the simulations in a system of atoms in a Mott-insulator state in a two-dimensional optical lattice, where recurrent scattering of light induces strong interatomic correlations. These correlations result in collective many-atom subradiant and superradiant states and a strong dependence of the response on the spatial confinement within the lattice sites.

  12. Angle resolved scatter measurement of bulk scattering in transparent ceramics

    NASA Astrophysics Data System (ADS)

    Sharma, Saurabh; Miller, J. Keith; Shori, Ramesh K.; Goorsky, Mark S.

    2015-02-01

    Bulk scattering in polycrystalline laser materials (PLM), due to non-uniform refractive index across the bulk, is regarded as the primary loss mechanism leading to degradation of laser performance with higher threshold and lower output power. The need for characterization techniques towards identifying bulk scatter and assessing the quality. Assessment of optical quality and the identification of bulk scatter have been by simple visual inspection of thin samples of PLMs, thus making the measurements highly subjective and inaccurate. Angle Resolved Scatter (ARS) measurement allows for the spatial mapping of scattered light at all possible angles about a sample, mapping the intensity for both forward scatter and back-scatter regions. The cumulative scattered light intensity, in the forward scatter direction, away from the specular beam is used for the comparison of bulk scattering between samples. This technique employ the detection of scattered light at all angles away from the specular beam directions and represented as a 2-D polar map. The high sensitivity of the ARS technique allows us to compare bulk scattering in different PLM samples which otherwise had similar transmitted beam wavefront distortions.

  13. Proton Nucleus Elastic Scattering Data.

    1993-08-18

    Version 00 The Proton Nucleus Elastic Scattering Data file PNESD contains the numerical data and the related bibliography for the differential elastic cross sections, polarization and integral nonelastic cross sections for elastic proton-nucleus scattering.

  14. Interface scattering in polycrystalline thermoelectrics

    SciTech Connect

    Popescu, Adrian; Haney, Paul M.

    2014-03-28

    We study the effect of electron and phonon interface scattering on the thermoelectric properties of disordered, polycrystalline materials (with grain sizes larger than electron and phonons' mean free path). Interface scattering of electrons is treated with a Landauer approach, while that of phonons is treated with the diffuse mismatch model. The interface scattering is embedded within a diffusive model of bulk transport, and we show that, for randomly arranged interfaces, the overall system is well described by effective medium theory. Using bulk parameters similar to those of PbTe and a square barrier potential for the interface electron scattering, we identify the interface scattering parameters for which the figure of merit ZT is increased. We find the electronic scattering is generally detrimental due to a reduction in electrical conductivity; however, for sufficiently weak electronic interface scattering, ZT is enhanced due to phonon interface scattering.

  15. Monte Carlo study of electron-beam penetration and backscattering in multi-walled carbon nanotube materials: The effect of different scattering models

    NASA Astrophysics Data System (ADS)

    Kyriakou, Ioanna; Emfietzoglou, Dimitris; Nojeh, Alireza; Moscovitch, Marko

    2013-02-01

    A systematic study of electron-beam penetration and backscattering in multi-walled carbon nanotube (MWCNT) materials for beam energies of ˜0.3 to 30 keV is presented based on event-by-event Monte Carlo simulation of electron trajectories using state-of-the-art scattering cross sections. The importance of different analytic approximations for computing the elastic and inelastic electron-scattering cross sections for MWCNTs is emphasized. We offer a simple parameterization for the total and differential elastic-scattering Mott cross section, using appropriate modifications to the Browning formula and the Thomas-Fermi screening parameter. A discrete-energy-loss approach to inelastic scattering based on dielectric theory is adopted using different descriptions of the differential cross section. The sensitivity of electron penetration and backscattering parameters to the underlying scattering models is examined. Our simulations confirm the recent experimental backscattering data on MWCNT forests and, in particular, the steep increase of the backscattering yield at sub-keV energies as well as the sidewalls escape effect at high-beam energies.

  16. Scattering fidelity in elastodynamics

    NASA Astrophysics Data System (ADS)

    Gorin, T.; Seligman, T. H.; Weaver, R. L.

    2006-01-01

    The recent introduction of the concept of scattering fidelity causes us to revisit the experiment by Lobkis and Weaver [Phys. Rev. Lett. 90, 254302 (2003)]. There, the “distortion” of the coda of an acoustic signal is measured under temperature changes. This quantity is, in fact, the negative logarithm of scattering fidelity. We reanalyze their experimental data for two samples, and we find good agreement with random matrix predictions for the standard fidelity. Usually, one may expect such an agreement for chaotic systems, only. While the first sample may indeed be assumed chaotic, for the second sample, a perfect cuboid, such an agreement is surprising. For the first sample, the random matrix analysis yields perturbation strengths compatible with semiclassical predictions. For the cuboid, the measured perturbation strengths are by a common factor of (5)/(3) too large. Apart from that, the experimental curves for the distortion are well reproduced.

  17. Coherent Scatter Imaging Measurements

    NASA Astrophysics Data System (ADS)

    Ur Rehman, Mahboob

    In conventional radiography, anatomical information of the patients can be obtained, distinguishing different tissue types, e.g. bone and soft tissue. However, it is difficult to obtain appreciable contrast between two different types of soft tissues. Instead, coherent x-ray scattering can be utilized to obtain images which can differentiate between normal and cancerous cells of breast. An x-ray system using a conventional source and simple slot apertures was tested. Materials with scatter signatures that mimic breast cancer were buried in layers of fat of increasing thickness and imaged. The result showed that the contrast and signal to noise ratio (SNR) remained high even with added fat layers and short scan times.

  18. Scattering problems in elastodynamics

    NASA Astrophysics Data System (ADS)

    Diatta, Andre; Kadic, Muamer; Wegener, Martin; Guenneau, Sebastien

    2016-09-01

    In electromagnetism, acoustics, and quantum mechanics, scattering problems can routinely be solved numerically by virtue of perfectly matched layers (PMLs) at simulation domain boundaries. Unfortunately, the same has not been possible for general elastodynamic wave problems in continuum mechanics. In this Rapid Communication, we introduce a corresponding scattered-field formulation for the Navier equation. We derive PMLs based on complex-valued coordinate transformations leading to Cosserat elasticity-tensor distributions not obeying the minor symmetries. These layers are shown to work in two dimensions, for all polarizations, and all directions. By adaptative choice of the decay length, the deep subwavelength PMLs can be used all the way to the quasistatic regime. As demanding examples, we study the effectiveness of cylindrical elastodynamic cloaks of the Cosserat type and approximations thereof.

  19. Syzygies probing scattering amplitudes

    NASA Astrophysics Data System (ADS)

    Chen, Gang; Liu, Junyu; Xie, Ruofei; Zhang, Hao; Zhou, Yehao

    2016-09-01

    We propose a new efficient algorithm to obtain the locally minimal generating set of the syzygies for an ideal, i.e. a generating set whose proper subsets cannot be generating sets. Syzygy is a concept widely used in the current study of scattering amplitudes. This new algorithm can deal with more syzygies effectively because a new generation of syzygies is obtained in each step and the irreducibility of this generation is also verified in the process. This efficient algorithm can also be applied in getting the syzygies for the modules. We also show a typical example to illustrate the potential application of this method in scattering amplitudes, especially the Integral-By-Part(IBP) relations of the characteristic two-loop diagrams in the Yang-Mills theory.

  20. Molecular-beam scattering

    SciTech Connect

    Vernon, M.F.

    1983-07-01

    The molecular-beam technique has been used in three different experimental arrangements to study a wide range of inter-atomic and molecular forces. Chapter 1 reports results of a low-energy (0.2 kcal/mole) elastic-scattering study of the He-Ar pair potential. The purpose of the study was to accurately characterize the shape of the potential in the well region, by scattering slow He atoms produced by expanding a mixture of He in N/sub 2/ from a cooled nozzle. Chapter 2 contains measurements of the vibrational predissociation spectra and product translational energy for clusters of water, benzene, and ammonia. The experiments show that most of the product energy remains in the internal molecular motions. Chapter 3 presents measurements of the reaction Na + HCl ..-->.. NaCl + H at collision energies of 5.38 and 19.4 kcal/mole. This is the first study to resolve both scattering angle and velocity for the reaction of a short lived (16 nsec) electronic excited state. Descriptions are given of computer programs written to analyze molecular-beam expansions to extract information characterizing their velocity distributions, and to calculate accurate laboratory elastic-scattering differential cross sections accounting for the finite apparatus resolution. Experimental results which attempted to determine the efficiency of optically pumping the Li(2/sup 2/P/sub 3/2/) and Na(3/sup 2/P/sub 3/2/) excited states are given. A simple three-level model for predicting the steady-state fraction of atoms in the excited state is included.

  1. Dynamic light scattering microscopy

    NASA Astrophysics Data System (ADS)

    Dzakpasu, Rhonda

    An optical microscope technique, dynamic light scattering microscopy (DLSM) that images dynamically scattered light fluctuation decay rates is introduced. Using physical optics we show theoretically that within the optical resolution of the microscope, relative motions between scattering centers are sufficient to produce significant phase variations resulting in interference intensity fluctuations in the image plane. The time scale for these intensity fluctuations is predicted. The spatial coherence distance defining the average distance between constructive and destructive interference in the image plane is calculated and compared with the pixel size. We experimentally tested DLSM on polystyrene latex nanospheres and living macrophage cells. In order to record these rapid fluctuations, on a slow progressive scan CCD camera, we used a thin laser line of illumination on the sample such that only a single column of pixels in the CCD camera is illuminated. This allowed the use of the rate of the column-by-column readout transfer process as the acquisition rate of the camera. This manipulation increased the data acquisition rate by at least an order of magnitude in comparison to conventional CCD cameras rates defined by frames/s. Analysis of the observed fluctuations provides information regarding the rates of motion of the scattering centers. These rates, acquired from each position on the sample are used to create a spatial map of the fluctuation decay rates. Our experiments show that with this technique, we are able to achieve a good signal-to-noise ratio and can monitor fast intensity fluctuations, on the order of milliseconds. DLSM appears to provide dynamic information about fast motions within cells at a sub-optical resolution scale and provides a new kind of spatial contrast.

  2. Calculating scattering amplitudes efficiently

    SciTech Connect

    Dixon, L.

    1996-01-01

    We review techniques for more efficient computation of perturbative scattering amplitudes in gauge theory, in particular tree and one- loop multi-parton amplitudes in QCD. We emphasize the advantages of (1) using color and helicity information to decompose amplitudes into smaller gauge-invariant pieces, and (2) exploiting the analytic properties of these pieces, namely their cuts and poles. Other useful tools include recursion relations, special gauges and supersymmetric rearrangements. 46 refs., 11 figs.

  3. Molecular-beam scattering

    NASA Astrophysics Data System (ADS)

    Vernon, M. F.

    1983-07-01

    The molecular-beam technique has been used in three different experimental arrangements to study a wide range of inter-atomic and molecular forces. Chapter 1 reports results of a low-energy (0.2 kcal/mole) elastic-scattering study of the He-Ar pair potential. The purpose of the study was to accurately characterize the shape of the potential in the well region, by scattering slow He atoms produced by expanding a mixture of He in N2 from a cooled nozzle. Chapter 2 contains measurements of the vibrational predissociation spectra and product translational energy for clusters of water, benzene, and ammonia. The experiments show that most of the product energy remains in the internal molecular motions. Chapter 3 presents measurements of the reaction Na + HC1 (FEMALE) NAC1 + H at collision energies of 5.38 and 19.4 kcal/mole. This is the first study to resolve both scattering angle and velocity for the reaction of a short lived (16 nsec) electronic excited state. Descriptions are given of computer programs written to analyze molecular-beam expansions to extract information characterizing their velocity distributions, and to calculate accurate laboratory elastic-scattering differential cross sections accounting for the finite apparatus resolution. Experimental results which attempted to determine the efficiency of optically pumping the Li(2(2)P/sub 3/2/) and Na(3(2)P/sub 3/2) excited states are given. A simple three-level model for predicting the steady-state fraction of atoms in the excited state is included.

  4. Concurrent electromagnetic scattering analysis

    NASA Technical Reports Server (NTRS)

    Patterson, Jean E.; Cwik, Tom; Ferraro, Robert D.; Jacobi, Nathan; Liewer, Paulett C.; Lockhart, Thomas G.; Lyzenga, Gregory A.; Parker, Jay

    1989-01-01

    The computational power of the hypercube parallel computing architecture is applied to the solution of large-scale electromagnetic scattering and radiation problems. Three analysis codes have been implemented. A Hypercube Electromagnetic Interactive Analysis Workstation was developed to aid in the design and analysis of metallic structures such as antennas and to facilitate the use of these analysis codes. The workstation provides a general user environment for specification of the structure to be analyzed and graphical representations of the results.

  5. Neutron scattering in Australia

    SciTech Connect

    Knott, R.B.

    1994-12-31

    Neutron scattering techniques have been part of the Australian scientific research community for the past three decades. The High Flux Australian Reactor (HIFAR) is a multi-use facility of modest performance that provides the only neutron source in the country suitable for neutron scattering. The limitations of HIFAR have been recognized and recently a Government initiated inquiry sought to evaluate the future needs of a neutron source. In essence, the inquiry suggested that a delay of several years would enable a number of key issues to be resolved, and therefore a more appropriate decision made. In the meantime, use of the present source is being optimized, and where necessary research is being undertaken at major overseas neutron facilities either on a formal or informal basis. Australia has, at present, a formal agreement with the Rutherford Appleton Laboratory (UK) for access to the spallation source ISIS. Various aspects of neutron scattering have been implemented on HIFAR, including investigations of the structure of biological relevant molecules. One aspect of these investigations will be presented. Preliminary results from a study of the interaction of the immunosuppressant drug, cyclosporin-A, with reconstituted membranes suggest that the hydrophobic drug interdigitated with lipid chains.

  6. Timelike Compton Scattering

    NASA Astrophysics Data System (ADS)

    Mkrtchyan, Arthur; Albayrak, Ibrahim; Horn, Tanja; Nadel-Turonski, Pawel

    2015-04-01

    Deeply Virtual Comtpon Scattering (DVCS) is deemed the simplest and cleanest way to access the Generalized Parton Distributions (GPDs) of the nucleon. The DVCS process interferes with the Bethe-Heitler process allowing one to access the DVCS amplitudes. The imaginary part of the Compton amplitude is now relatively well understood, primarily through measurements of DVCS. However, much less is known about the real part of the amplitude. Time-like Compton Scattering (TCS) is the inverse process of DVCS and provides a new and promising way for probing the real part of the amplitude, and so constraining GPDs. Comparing data from Time-like Compton Scattering and the space-like DVCS process will also allow for testing the universality of GPDs. First studies of TCS using real tagged and quasi-real untagged photons were carried out at Jefferson Lab 6 GeV. In this talk, preliminary results on asymmetries and extraction of the real part of the CFF using photoproduction data and a comparison to electroproduction data will be presented. We will also discuss future plans for dilepton production at Jefferson Lab 12 GeV. Supported in part by NSF Grant PHY-1306227.

  7. Nanowire Electron Scattering Spectroscopy

    NASA Technical Reports Server (NTRS)

    Hunt, Brian; Bronikowsky, Michael; Wong, Eric; VonAllmen, Paul; Oyafuso, Fablano

    2009-01-01

    Nanowire electron scattering spectroscopy (NESS) has been proposed as the basis of a class of ultra-small, ultralow-power sensors that could be used to detect and identify chemical compounds present in extremely small quantities. State-of-the-art nanowire chemical sensors have already been demonstrated to be capable of detecting a variety of compounds in femtomolar quantities. However, to date, chemically specific sensing of molecules using these sensors has required the use of chemically functionalized nanowires with receptors tailored to individual molecules of interest. While potentially effective, this functionalization requires labor-intensive treatment of many nanowires to sense a broad spectrum of molecules. In contrast, NESS would eliminate the need for chemical functionalization of nanowires and would enable the use of the same sensor to detect and identify multiple compounds. NESS is analogous to Raman spectroscopy, the main difference being that in NESS, one would utilize inelastic scattering of electrons instead of photons to determine molecular vibrational energy levels. More specifically, in NESS, one would exploit inelastic scattering of electrons by low-lying vibrational quantum states of molecules attached to a nanowire or nanotube.

  8. Light Scattering by Spheroids

    NASA Astrophysics Data System (ADS)

    Xie, Ya-Ming; Ji, Xia

    Nowadays, with the development of technology, particles with size at nanoscale have been synthesized in experiments. It is noticed that anisotropy is an unavoidable problem in the production of nanospheres. Besides, nonspherical nanoparticles have also been extensively used in experiments. Comparing with spherical model, spheroidal model can give a better description for the characteristics of nonspherical particles. Thus the study of analytical solution for light scattering by spheroidal particles has practical implications. By expanding incident, scattered, and transmitted electromagnetic fields in terms of appropriate vector spheroidal wave functions, an analytic solution is obtained to the problem of light scattering by spheroids. Unknown field expansion coefficients can be determined with the combination of boundary conditions and rotational-translational addition theorems for vector spheroidal wave functions. Based on the theoretical derivation, a Fortran code has been developed to calculate the extinction cross section and field distribution, whose results agree well with those obtain by FDTD simulation. This research is supported by the National Natural Science Foundation of China No. 91230203.

  9. Rutherford scattering of electron vortices

    NASA Astrophysics Data System (ADS)

    Van Boxem, Ruben; Partoens, Bart; Verbeeck, Johan

    2014-03-01

    By considering a cylindrically symmetric generalization of a plane wave, the first-order Born approximation of screened Coulomb scattering unfolds two new dimensions in the scattering problem: transverse momentum and orbital angular momentum of the incoming beam. In this paper, the elastic Coulomb scattering amplitude is calculated analytically for incoming Bessel beams. This reveals novel features occurring for wide-angle scattering and quantitative insights for small-angle vortex scattering. The result successfully generalizes the well-known Rutherford formula, incorporating transverse and orbital angular momentum into the formalism.

  10. Rainbow scattering in nuclear collisions

    SciTech Connect

    Berezhnoi-breve, Y.A.; Kuznichenko, A.V.; Onishchenko, G.M.; Pilipenko, V.V.

    1987-03-01

    The evolution of ideas about the rainbow phenomenon resulting from the refraction and reflection of light in water drops is briefly reviewed. The rainbow scattering of particles in quantum mechanics is treated on the basis of the semiclassical approximation, and the nuclear and Coulomb ''rainbows'' are discussed. Rainbow scattering of light ions by nuclei at energies Eapprox. >25--30 MeV/nucleon is considered. The results of theoretical analysis of experimental data on rainbow scattering are presented. The behavior of the nuclear part of the scattering phase shift deduced from experiment is discussed. The manifestation of rainbow scattering in quasielastic nuclear processes is considered.

  11. Gravitational scattering of electromagnetic radiation

    NASA Technical Reports Server (NTRS)

    Brooker, J. T.; Janis, A. I.

    1980-01-01

    The scattering of electromagnetic radiation by linearized gravitational fields is studied to second order in a perturbation expansion. The incoming electromagnetic radiation can be of arbitrary multipole structure, and the gravitational fields are also taken to be advanced fields of arbitrary multipole structure. All electromagnetic multipole radiation is found to be scattered by gravitational monopole and time-varying dipole fields. No case has been found, however, in which any electromagnetic multipole radiation is scattered by gravitational fields of quadrupole or higher-order multipole structure. This lack of scattering is established for infinite classes of special cases, and is conjectured to hold in general. The results of the scattering analysis are applied to the case of electromagnetic radiation scattered by a moving mass. It is shown how the mass and velocity may be determined by a knowledge of the incident and scattered radiation.

  12. Improved scatter correction using adaptive scatter kernel superposition

    NASA Astrophysics Data System (ADS)

    Sun, M.; Star-Lack, J. M.

    2010-11-01

    Accurate scatter correction is required to produce high-quality reconstructions of x-ray cone-beam computed tomography (CBCT) scans. This paper describes new scatter kernel superposition (SKS) algorithms for deconvolving scatter from projection data. The algorithms are designed to improve upon the conventional approach whose accuracy is limited by the use of symmetric kernels that characterize the scatter properties of uniform slabs. To model scatter transport in more realistic objects, nonstationary kernels, whose shapes adapt to local thickness variations in the projection data, are proposed. Two methods are introduced: (1) adaptive scatter kernel superposition (ASKS) requiring spatial domain convolutions and (2) fast adaptive scatter kernel superposition (fASKS) where, through a linearity approximation, convolution is efficiently performed in Fourier space. The conventional SKS algorithm, ASKS, and fASKS, were tested with Monte Carlo simulations and with phantom data acquired on a table-top CBCT system matching the Varian On-Board Imager (OBI). All three models accounted for scatter point-spread broadening due to object thickening, object edge effects, detector scatter properties and an anti-scatter grid. Hounsfield unit (HU) errors in reconstructions of a large pelvis phantom with a measured maximum scatter-to-primary ratio over 200% were reduced from -90 ± 58 HU (mean ± standard deviation) with no scatter correction to 53 ± 82 HU with SKS, to 19 ± 25 HU with fASKS and to 13 ± 21 HU with ASKS. HU accuracies and measured contrast were similarly improved in reconstructions of a body-sized elliptical Catphan phantom. The results show that the adaptive SKS methods offer significant advantages over the conventional scatter deconvolution technique.

  13. Scattering Solar Thermal Concentrators

    SciTech Connect

    Giebink, Noel C.

    2015-01-31

    This program set out to explore a scattering-based approach to concentrate sunlight with the aim of improving collector field reliability and of eliminating wind loading and gross mechanical movement through the use of a stationary collection optic. The approach is based on scattering sunlight from the focal point of a fixed collection optic into the confined modes of a sliding planar waveguide, where it is transported to stationary tubular heat transfer elements located at the edges. Optical design for the first stage of solar concentration, which entails focusing sunlight within a plane over a wide range of incidence angles (>120 degree full field of view) at fixed tilt, led to the development of a new, folded-path collection optic that dramatically out-performs the current state-of-the-art in scattering concentration. Rigorous optical simulation and experimental testing of this collection optic have validated its performance. In the course of this work, we also identified an opportunity for concentrating photovoltaics involving the use of high efficiency microcells made in collaboration with partners at the University of Illinois. This opportunity exploited the same collection optic design as used for the scattering solar thermal concentrator and was therefore pursued in parallel. This system was experimentally demonstrated to achieve >200x optical concentration with >70% optical efficiency over a full day by tracking with <1 cm of lateral movement at fixed latitude tilt. The entire scattering concentrator waveguide optical system has been simulated, tested, and assembled at small scale to verify ray tracing models. These models were subsequently used to predict the full system optical performance at larger, deployment scale ranging up to >1 meter aperture width. Simulations at an aperture widths less than approximately 0.5 m with geometric gains ~100x predict an overall optical efficiency in the range 60-70% for angles up to 50 degrees from normal. However, the

  14. Raman scattering in crystals

    SciTech Connect

    Edwards, D.F.

    1988-09-30

    A tutorial presentation is given of Raman scattering in crystals. The physical concepts are emphasized rather than the detailed mathematical formalism. Starting with an introduction to the concepts of phonons and conservation laws, the effects of photon-phonon interactions are presented. This interaction concept is shown for a simple cubic crystal and is extended to a uniaxial crystal. The correlation table method is used for determining the number and symmetry of the Raman active modes. Finally, examples are given to illustrate the relative ease of using this group theoretical method and the predictions are compared with measured Raman spectra. 37 refs., 17 figs., 6 tabs.

  15. A New Polyethylene Scattering Law Determined Using Inelastic Neutron Scattering

    SciTech Connect

    Lavelle, Christopher M; Liu, C; Stone, Matthew B

    2013-01-01

    Monte Carlo neutron transport codes such as MCNP rely on accurate data for nuclear physics cross-sections to produce accurate results. At low energy, this takes the form of scattering laws based on the dynamic structure factor, S (Q, E). High density polyethylene (HDPE) is frequently employed as a neutron moderator at both high and low temperatures, however the only cross-sections available are for T =300 K, and the evaluation has not been updated in quite some time. In this paper we describe inelastic neutron scattering measurements on HDPE at 5 and 300 K which are used to improve the scattering law for HDPE. We describe the experimental methods, review some of the past HDPE scattering laws, and compare computations using these models to the measured S (Q, E). The total cross-section is compared to available data, and the treatment of the carbon secondary scatterer as a free gas is assessed. We also discuss the use of the measurement itself as a scattering law via the 1 phonon approximation. We show that a scattering law computed using a more detailed model for the Generalized Density of States (GDOS) compares more favorably to this experiment, suggesting that inelastic neutron scattering can play an important role in both the development and validation of new scattering laws for Monte Carlo work.

  16. Polarization of inverse plasmon scattering

    NASA Technical Reports Server (NTRS)

    Windsor, R. A.; Kellogg, P. J.

    1974-01-01

    The scattering of electrostatic plasma waves by a flux of ultrarelativistic electrons passing through a plasma gives rise to a radiation spectrum which is similar to a synchrotron radiation spectrum. This mechanism, first considered by Gailitis and Tsytovich, is analagous to inverse Compton scattering, and we have named it inverse plasmon scattering. For a power-law electron flux, both inverse plasmon scattering and synchrotron radiation have the same spectral index. In an attempt to distinguish between these mechanisms, we have calculated the polarization level expected from inverse plasmon scattering. The polarization level found is similar to that obtained from a synchrotron radiation source. This means that the radiation produced by two mechanisms, synchrotron radiation and inverse plasmon scattering, is indistinguishable; and this attempt to differentiate between them by polarization effects has been unsuccessful.

  17. Coherent scattering of cosmic neutrinos

    NASA Technical Reports Server (NTRS)

    Opher, R.

    1974-01-01

    It is shown that cosmic neutrino scattering can be non-negligible when coherence effects previously neglected are taken into account. The coherent neutrino scattering cross section is derived and the neutrino index of refraction evaluated. As an example of coherent neutrino scattering, a detector using critical reflection is described which in principle can detect the low energy cosmic neutrino background allowed by the measured cosmological red shift.

  18. Electromagnetic scattering from turbulent plasmas

    SciTech Connect

    Resendes, D.G. Instituto Superior Tecnico, Rua Rovisco Pais, Lisboa )

    1992-11-15

    A self-consistent multiple-scattering theory of vector electromagnetic waves scattered from a turbulent plasma is presented. This approach provides a general and systematic treatment to all orders in turbulence of the scattering of electromagnetic waves in terms of the properties of the turbulent structure of the scattering system and is applicable in the full regime from underdense to overdense plasmas. To illustrate the theory, a plasma consisting of a finite number density of discrete scatterers with a simple geometry and statistical properties is chosen. In this approach the exact solution for a single scatterer is obtained first. From it the configuration-dependent solution for {ital N} scatterers is constructed. Rather than solving explicitly for this solution and then averaging, the averaging operation will be taken first in order to find an approximate equation obeyed by the mean or coherent field. The coherent and incoherent scattering are then determined in terms of the coherent field and the backscatter is evaluated. The coherent and incoherent scattering, our principal results, are expressed in a plane-wave basis in a form suitable for numerical computation. A number of interesting phenomena which may readily be incorporated into the theory are indicated.

  19. Born approximation, scattering, and algorithm

    NASA Astrophysics Data System (ADS)

    Martinez, Alex; Hu, Mengqi; Gu, Haicheng; Qiao, Zhijun

    2015-05-01

    In the past few decades, there were many imaging algorithms designed in the case of the absence of multiple scattering. Recently, we discussed an algorithm for removing high order scattering components from collected data. This paper is a continuation of our previous work. First, we investigate the current state of multiple scattering in SAR. Then, we revise our method and test it. Given an estimate of our target reflectivity, we compute the multi scattering effects in the target region for various frequencies. Furthermore, we propagate this energy through free space towards our antenna, and remove it from the collected data.

  20. A study of X100 pipeline steel passivation in mildly alkaline bicarbonate solutions using electrochemical impedance spectroscopy under potentiodynamic conditions and Mott-Schottky

    NASA Astrophysics Data System (ADS)

    Gadala, Ibrahim M.; Alfantazi, Akram

    2015-12-01

    The key steps involved in X100 pipeline steel passivation in bicarbonate-based simulated soil solutions from the pre-passive to transpassive potential regions have been analyzed here using a step-wise anodizing-electrochemical impedance spectroscopy (EIS) routine. Pre-passive steps involve parallel dissolution-adsorption in early stages followed by clear diffusion-adsorption control shortly before iron hydroxide formation. Aggressive NS4 chlorides/sulfate promote steel dissolution whilst inhibiting diffusion in pre-passive steps. Diffusive and adsorptive effects remain during iron hydroxide formation, but withdraw shortly thereafter during its removal and the development of the stable iron carbonate passive layer. Passive layer protectiveness is evaluated using EIS fitting, current density analysis, and correlations with semiconductive parameters, consistently revealing improved robustness in colder, bicarbonate-rich, chloride/sulfate-free conditions. Ferrous oxide formation at higher potentials results in markedly lower impedances with disordered behavior, and the involvement of the iron(III) valence state is observed in Mott-Schottky tests exclusively for 75 °C conditions.

  1. Corrosion, ion release and Mott-Schottky probe of chromium oxide coatings in saline solution with potential for orthopaedic implant applications

    NASA Astrophysics Data System (ADS)

    Ogwu, A. A.; Oje, A. M.; Kavanagh, J.

    2016-04-01

    We report our investigation on chromium oxide thin film coatings that show a negligible ion release during electrochemical corrosion testing in saline solution. The chemical constituents of the films prepared by reactive magnetron sputtering were identified to be predominantly Cr2O3 based on Raman spectroscopy anti-symmetric stretching vibration modes for CrIII-O and other peaks and an FTIR spectroscopy E u vibrational mode at 409 cm-1. X-ray photoelectron spectroscopy, multiplet fitting for 2P 3/2 and 2P 1/2 states also confirmed the predominantly Cr2O3 stoichiometry in the films. The prepared chromium oxide coatings showed superior pitting corrosion resistance compared to the native chromium oxide films on bare uncoated stainless steel when tested under open circuit potential, potentiodynamic polarisation and cyclic voltammetry in saline solution. The chromium ion released into solution during the corrosion testing of stainless steel substrates coated with chromium oxide coatings was found to be negligibly small based on atomic absorption spectroscopy measurements. Our Mott-Schottky analysis investigation showed that the negligibly small ion release from the chromium oxide coated steel substrates is most likely due to a much lower defect density on the surface of the deposited coatings compared to the native oxide layer on the uncoated steel substrates. This opens up the opportunity for using chromium oxide surface coatings in hip, knee and other orthopaedic implants where possible metal ion release in vivo still poses a great challenge.

  2. Modification of Mott phase transition characteristics in VO2@TiO2 core/shell nanostructures by misfit-strained heteroepitaxy.

    PubMed

    Li, Yamei; Ji, Shidong; Gao, Yanfeng; Luo, Hongjie; Jin, Ping

    2013-07-24

    Vanadium dioxide (VO2) is a key material for thermochromic smart windows that can respond to environmental temperature and modulate near-infrared irradiation by changing from a transparent state at low temperature to a more reflective state at high temperature, while maintaining visible transmittance. Here, we demonstrate for the first time that the Mott phase transition characteristics in VO2 nanoparticles can be remarkably modified by misfit strains occurring at the epitaxial interface between VO2 and the anatase TiO2 of VO2/TiO2 core-shell particles. The heteroepitaxial growth of the as-synthesized particles followed an unprecedented orientation relationship, and an epitaxial growth mechanism is proposed to explain this behavior. A relatively small theoretical coherent misfit (3-11%) and a moderate heating rate (20 °C·min(-1)) in the preparation of the core-shell structure were critically important from the thermodynamic and kinetic perspectives, respectively. The misfit-induced interfacial strain along the uniaxial cR axis increased the transition temperatures, especially on the cooling portion of the heating-cooling cycle, leading to a notably reduced transition hysteresis loop width (from 23.5 to 12.0 °C). Moreover, the optical band gap was also engineered by the interfacial effect. Such a reduced hysteresis showed a benefit for enhancing a rapid response for energy saving thermochromic smart windows. PMID:23777607

  3. Predictive Capability for Strongly Correlated Systems: Mott Transition in MnO, Multielectron Magnetic Moments, and Dynamics Effects in Correlated Materials

    SciTech Connect

    Krakauer, Henry; Zhang, Shiwei

    2013-02-21

    There are classes of materials that are important to DOE and to the science and technology community, generically referred to as strongly correlated electron systems (SCES), which have proven very difficult to understand and to simulate in a material-specific manner. These range from actinides, which are central to the DOE mission, to transition metal oxides, which include the most promising components of new spin electronics applications as well as the high temperature superconductors, to intermetallic compounds whose heavy fermion characteristics and quantum critical behavior has given rise to some of the most active areas in condensed matter theory. The objective of the CMSN cooperative research team was to focus on the application of these new methodologies to the specific issue of Mott transitions, multi-electron magnetic moments, and dynamical properties correlated materials. Working towards this goal, the W&M team extended its first-principles phaseless auxiliary-field quantum Monte Carlo (AFQMC) method to accurately calculate structural phase transitions and excited states.

  4. Dust properties from scattering

    NASA Astrophysics Data System (ADS)

    Lefèvre, C.; Pagani, L.; Min, M.; Poteet, C.; Whittet, D.; Cambrésy, L.

    2016-05-01

    Dust grains evolve during the life cycle of the interstellar matter. From their birth places to dense molecular clouds, they grow by coagulation and acquire ice mantles, mainly composed of water. These morphological changes affect their optical properties. However, it remains a highly degenerate issue to determine their composition, size distribution, and shape from observations. In particular, using wavelengths associated to dust emission alone is not sufficient to investigate dense cold cores. Fortunately, scattering has turned out to be a powerful tool to investigate molecular clouds from the outer regions to the core. In particular, it is possible to quantify the amount of dust aggregates needed to reproduce observations from 1.25 to 8 μm.

  5. Elliptic scattering equations

    NASA Astrophysics Data System (ADS)

    Cardona, Carlos; Gomez, Humberto

    2016-06-01

    Recently the CHY approach has been extended to one loop level using elliptic functions and modular forms over a Jacobian variety. Due to the difficulty in manipulating these kind of functions, we propose an alternative prescription that is totally algebraic. This new proposal is based on an elliptic algebraic curve embedded in a mathbb{C}{P}^2 space. We show that for the simplest integrand, namely the n - gon, our proposal indeed reproduces the expected result. By using the recently formulated Λ-algorithm, we found a novel recurrence relation expansion in terms of tree level off-shell amplitudes. Our results connect nicely with recent results on the one-loop formulation of the scattering equations. In addition, this new proposal can be easily stretched out to hyperelliptic curves in order to compute higher genus.

  6. Stimulated rotational Raman scattering

    NASA Astrophysics Data System (ADS)

    Parazzoli, C. G.; Rafanelli, G. L.; Capps, D. M.; Drutman, C.

    1989-03-01

    The effect of Stimulated Rotational Raman Scattering (SRRS) processes on high energy laser directed energy weapon systems was studied. The program had 3 main objectives; achieving an accurate description of the physical processes involved in SRRS; developing a numerical algorithm to confidently evaluate SRRS-induced losses in the propagation of high energy laser beams in the uplink and downlink segments of the optical trains of various strategic defense system scenarios; and discovering possible methods to eliminate, or at least reduce, the deleterious effects of SRRS on the energy deposition on target. The following topics are discussed: the motivation for the accomplishments of the DOE program; the Semiclassical Theory of Non-Resonant SRRS for Diatomic Homonuclear Molecules; and then the following appendices; Calculation of the Dipole Transition Reduced Matrix Element, Guided Tour of Hughes SRRS Code, Running the Hughes SRRS Code, and Hughes SRRS Code Listing.

  7. Neutron Scattering Stiudies

    SciTech Connect

    Kegel, Gunter H.R.; Egan, James J

    2007-04-18

    This project covers four principal areas of research: Elastic and inelastic neutron scattering studies in odd-A terbium, thulium and other highly deformed nuclei near A=160 with special regard to interband transitions and to the investigation of the direct-interaction versus the compound-nucleus excitation process in these nuclei. Examination of new, fast photomultiplier tubes suitable for use in a miniaturized neutron-time-of-flight spectrometer. Measurement of certain inelastic cross sections of 238U. Determination of the multiplicity of prompt fission gamma rays in even-A fissile actinides. Energies and mean lives of fission isomers produced by fast fission of even-Z, even-A actinides. Study of the mean life of 7Be in different host matrices and its possible astro-physical significance.

  8. Polarimetric scattering from layered media with multiple species of scatterers

    NASA Technical Reports Server (NTRS)

    Nghiem, S. V.; Kwok, R.; Yueh, S. H.; Kong, J. A.; Hsu, C. C.; Tassoudji, M. A.; Shin, R. T.

    1995-01-01

    Geophysical media are usually heterogeneous and contain multiple species of scatterers. In this paper a model is presented to calculate effective permittivities and polarimetric backscattering coefficients of multispecies-layered media. The same physical description is consistently used in the derivation of both permittivities and scattering coefficients. The strong permittivity fluctuation theory is extended to account for the multiple species of scatterers with a general ellipsoidal shape whose orientations are randomly distributed. Under the distorted Born approximation, polarimetric scattering coefficients are obtained. These calculations are applicable to the special cases of spheroidal and spherical scatterers. The model is used to study effects of scatterer shapes and multispecies mixtures on polarimetric signatures of heterogeneous media. The multispecies model accounts for moisture content in scattering media such as snowpack in an ice sheet. The results indicate a high sensitivity of backscatter to moisture with a stronger dependence for drier snow and ice grain size is important to the backscatter. For frost-covered saline ice, model results for bare ice are compared with measured data at C band and then the frost flower formation is simulated with a layer of fanlike ice crystals including brine infiltration over a rough interface. The results with the frost cover suggest a significant increase in scattering coefficients and a polarimetric signature closer to isotropic characteristics compared to the thin saline ice case.

  9. Forward-scatter radiant mapping

    NASA Technical Reports Server (NTRS)

    Jones, James; Webster, A. R.

    1992-01-01

    Forward-scatter systems have been much neglected for the study of meteors and meteor streams. A great deal of this neglect stems from the complicated geometry which has made the interpretation of results difficult in the past. This no longer presents a problem because of the computer power now available. There are practical advantages in using forward-scatter in that low-power transmitters are much easier to handle than the high-power ones used in pulsed back-scatter radars. The data reduction of the CW signals is also significantly simpler. Because the forward-scatter reflection geometry increases the duration of the echoes relative to the back-scatter case, the problem of the underdense ceiling is partially alleviated. We have built a 'short hop' forward-scatter system between Ottawa and London (Ont) for which the transmitter and receiver are separated by about 500 km. With it, we are able to measure unambiguously the directions of arrival of the echoes using a 5-antenna interferometer. Morton and Jones (1982, MN, 198, 737) have shown how the echo direction distribution can be deconvolved to yield the meteor radiant distribution for back-scatter data. We have extended the technique to the forward-scatter case and present some preliminary meteor radiant distribution maps.

  10. Scattering theory for arbitrary potentials

    SciTech Connect

    Kadyrov, A.S.; Bray, I.; Stelbovics, A.T.; Mukhamedzhanov, A.M.

    2005-09-15

    The fundamental quantities of potential scattering theory are generalized to accommodate long-range interactions. Definitions for the scattering amplitude and wave operators valid for arbitrary interactions including potentials with a Coulomb tail are presented. It is shown that for the Coulomb potential the generalized amplitude gives the physical on-shell amplitude without recourse to a renormalization procedure.

  11. Raman and fluorescence characteristics of resonant inelastic X-ray scattering from doped superconducting cuprates

    DOE PAGESBeta

    Huang, H. Y.; Jia, C. J.; Chen, Z. Y.; Wohlfeld, K.; Moritz, B.; Devereaux, T. P.; Wu, W. B.; Okamoto, J.; Lee, W. S.; Hashimoto, M.; et al

    2016-01-22

    Measurements of spin excitations are essential for an understanding of spin-mediated pairing for superconductivity; and resonant inelastic X-ray scattering (RIXS) provides a considerable opportunity to probe high-energy spin excitations. However, whether RIXS correctly measures the collective spin excitations of doped superconducting cuprates remains under debate. Here we demonstrate distinct Raman- and fluorescence-like RIXS excitations of Bi1.5Pb0.6Sr1.54CaCu2O8+δ. Combining photon-energy and momentum dependent RIXS measurements with theoretical calculations using exact diagonalization provides conclusive evidence that the Raman-like RIXS excitations correspond to collective spin excitations, which are magnons in the undoped Mott insulators and evolve into paramagnons in doped superconducting compounds. In contrast,more » the fluorescence-like shifts are due primarily to the continuum of particle-hole excitations in the charge channel. Our results show that under the proper experimental conditions RIXS indeed can be used to probe paramagnons in doped high-Tc cuprate superconductors.« less

  12. A high-efficiency spin-resolved photoemission spectrometer combining time-of-flight spectroscopy with exchange-scattering polarimetry.

    PubMed

    Jozwiak, C; Graf, J; Lebedev, G; Andresen, N; Schmid, A K; Fedorov, A V; El Gabaly, F; Wan, W; Lanzara, A; Hussain, Z

    2010-05-01

    We describe a spin-resolved electron spectrometer capable of uniquely efficient and high energy resolution measurements. Spin analysis is obtained through polarimetry based on low-energy exchange scattering from a ferromagnetic thin-film target. This approach can achieve a similar analyzing power (Sherman function) as state-of-the-art Mott scattering polarimeters, but with as much as 100 times improved efficiency due to increased reflectivity. Performance is further enhanced by integrating the polarimeter into a time-of-flight (TOF) based energy analysis scheme with a precise and flexible electrostatic lens system. The parallel acquisition of a range of electron kinetic energies afforded by the TOF approach results in an order of magnitude (or more) increase in efficiency compared to hemispherical analyzers. The lens system additionally features a 90 degrees bandpass filter, which by removing unwanted parts of the photoelectron distribution allows the TOF technique to be performed at low electron drift energy and high energy resolution within a wide range of experimental parameters. The spectrometer is ideally suited for high-resolution spin- and angle-resolved photoemission spectroscopy (spin-ARPES), and initial results are shown. The TOF approach makes the spectrometer especially ideal for time-resolved spin-ARPES experiments. PMID:20515152

  13. A high-efficiency spin-resolved photoemission spectrometer combining time-of-flight spectroscopy with exchange-scattering polarimetry

    NASA Astrophysics Data System (ADS)

    Jozwiak, C.; Graf, J.; Lebedev, G.; Andresen, N.; Schmid, A. K.; Fedorov, A. V.; El Gabaly, F.; Wan, W.; Lanzara, A.; Hussain, Z.

    2010-05-01

    We describe a spin-resolved electron spectrometer capable of uniquely efficient and high energy resolution measurements. Spin analysis is obtained through polarimetry based on low-energy exchange scattering from a ferromagnetic thin-film target. This approach can achieve a similar analyzing power (Sherman function) as state-of-the-art Mott scattering polarimeters, but with as much as 100 times improved efficiency due to increased reflectivity. Performance is further enhanced by integrating the polarimeter into a time-of-flight (TOF) based energy analysis scheme with a precise and flexible electrostatic lens system. The parallel acquisition of a range of electron kinetic energies afforded by the TOF approach results in an order of magnitude (or more) increase in efficiency compared to hemispherical analyzers. The lens system additionally features a 90° bandpass filter, which by removing unwanted parts of the photoelectron distribution allows the TOF technique to be performed at low electron drift energy and high energy resolution within a wide range of experimental parameters. The spectrometer is ideally suited for high-resolution spin- and angle-resolved photoemission spectroscopy (spin-ARPES), and initial results are shown. The TOF approach makes the spectrometer especially ideal for time-resolved spin-ARPES experiments.

  14. A high-efficiency spin-resolved photoemission spectrometer combining time-of-flight spectroscopy with exchange-scattering polarimetry

    SciTech Connect

    Jozwiak, Chris M.; Graff, Jeff; Lebedev, Gennadi; Andresen, Nord; Schmid, Andreas; Fedorov, Alexei; El Gabaly, Farid; Wan, Weishi; Lanzara, Alessandra; Hussain, Zahid

    2010-04-13

    We describe a spin-resolved electron spectrometer capable of uniquely efficient and high energy resolution measurements. Spin analysis is obtained through polarimetry based on low-energy exchange scattering from a ferromagnetic thin-film target. This approach can achieve a similar analyzing power (Sherman function) as state-of-the-art Mott scattering polarimeters, but with as much as 100 times improved efficiency due to increased reflectivity. Performance is further enhanced by integrating the polarimeter into a time-of-flight (TOF) based energy analysis scheme with a precise and flexible electrostatic lens system. The parallel acquisition of a range of electron kinetic energies afforded by the TOF approach results in an order of magnitude (or more) increase in efficiency compared to hemispherical analyzers. The lens system additionally features a 90 degrees bandpass filter, which by removing unwanted parts of the photoelectron distribution allows the TOF technique to be performed at low electron drift energy and high energy resolution within a wide range of experimental parameters. The spectrometer is ideally suited for high-resolution spin- and angle-resolved photoemission spectroscopy (spin-ARPES), and initial results are shown. The TOF approach makes the spectrometer especially ideal for time-resolved spin-ARPES experiments.

  15. Electron Scattering from Nuclei

    SciTech Connect

    J. Wallace Van Orden

    2002-08-01

    The description of nuclei at distances on the order of a fermi or less poses a difficult challenge for theoretical physicists. At larger distances the traditional description of the nucleus as a collection of interacting nucleons has been quite successful and substantial progress has been made in recent years in describing few-nucleon systems using this approach. However, it has been known for several decades that the nucleons themselves are composite objects which are believed to be described by Quantum Chromodynamics (QCD). QCD is a complicated nonlinear strongly interacting field theory which can only be used for calculation in special circumstances. Due to the property of asymptotic freedom exhibited by QCD, perturbative calculations of QCD can be made at large momentum transfers and have achieved substantial success for a variety of processes. Understanding the transition from traditional pictures of nuclei to QCD is a substantial challenge. As an example of this problem, this paper describes recent calculations of elastic electron-deuteron scattering based on a relativistic extension of the traditional nuclear physics approach. The results of this work are compared to new data obtained at the Thomas Jefferson National Laboratory and to the predictions of perturbative QCD.

  16. Temporal Scattering And Response

    1992-12-15

    TSAR2.3 (Temporal Scattering and Response) is a finite-difference time-domain electromagnetics code suite. TSAR2.3 is a software package for simulating the interactions of electromagnetic waves with linear materials through the use of the finite-difference time-domain method. The code suite contains grid generation, grid verification, input-file creation and post-processing utilities. The physics package, written in Fortran 77, can be pre-processed to run on many different architectures including Cray, Vax and many Unix workstations. Tools are provided tomore » easily port the code to new computers. The physics package is an efficient, flexible electromagnetic simulator. A body under study can be represented as a three-dimensional grid of materials with arbitrary linear properties. This grid can be simulated in a number of ways including incident plane waves, dipoles, and arbitrary incident fields. The grid can be terminated with numerous boundary conditions including free-space radiation, electric conductor, or magnetic conductor. Projection to the far-field in both the time and frequency domains is possible. This distribution includes make files for installing and maintaining the entire code suite.« less

  17. Temporal Scattering And Response

    SciTech Connect

    McLeod, R. R.; Ray, S. L.; Laguna, G.; Allison, M.; Cabral, B.

    1992-12-15

    TSAR2.3 (Temporal Scattering and Response) is a finite-difference time-domain electromagnetics code suite. TSAR2.3 is a software package for simulating the interactions of electromagnetic waves with linear materials through the use of the finite-difference time-domain method. The code suite contains grid generation, grid verification, input-file creation and post-processing utilities. The physics package, written in Fortran 77, can be pre-processed to run on many different architectures including Cray, Vax and many Unix workstations. Tools are provided to easily port the code to new computers. The physics package is an efficient, flexible electromagnetic simulator. A body under study can be represented as a three-dimensional grid of materials with arbitrary linear properties. This grid can be simulated in a number of ways including incident plane waves, dipoles, and arbitrary incident fields. The grid can be terminated with numerous boundary conditions including free-space radiation, electric conductor, or magnetic conductor. Projection to the far-field in both the time and frequency domains is possible. This distribution includes make files for installing and maintaining the entire code suite.

  18. Separating Scattering from Intrinsic Attenuation

    NASA Astrophysics Data System (ADS)

    van Wijk, K.; Scales, J. A.

    2003-12-01

    The subsurface appears disordered at all length-scales. Therefore, wave propatation at seismic or ultrasonic frequencies is subject to complicated scatterings. A pulse propagating in the subsurface loses energy at each scattering off an impedance contrast, but also decreases in amplitude as the impulse interacts with fluids in the rock. We call the latter non-elastic effect "intrinsic Q", while the former is "scattering Q". It is often the fluids in the rocks that are of interest, but conventional reflection and transmission of the incident pulse only cannot deceipher the individual components of Q due to scattering and fluid movement in the pore-space. We present an approach that can unravel these two mechanisms, allowing a separate estimate of absorption. This method treats the propagation of the average intensity in the framework of radiative transfer (RT); the arrival of (what is left of) the incident pulse is modeled as the coherent energy, whereas the later arriving multiply scattered events form the incoherent intensity. The coherent pulse decays exponentially due to a combination of scattering and absorption, and so does the incoherent intensity. However, multiple scattering can re-direct energy back to the receiver, supplying a gain-term at later times that makes up the incoherent intensity. Strictly speaking, one can invert for scattering and absorption from the intensity at late times only, often modeled with the late-time equivalent of RT, diffusion. However, we will show that fitting both early- and late-time signal with RT constrains absorption and scattering constants more rigorously. These ideas are illustrated by laboratory and sonic-logging measurements.

  19. Theoretical investigation on the pumping effect of stimulated Brillouin scattering on stimulated Raman scattering in water

    NASA Astrophysics Data System (ADS)

    Shi, J.; Chen, X.; Ouyang, M.; Gong, W.; Su, Y.; Liu, D.

    2012-02-01

    The pumping effect of stimulated Brillouin scattering on stimulated Raman scattering is investigated theoretically through the coupled wave equations of stimulated Brillouin scattering and stimulated Raman scattering. The numerical simulations are in agreement with the experimental results. They indicate that the backward stimulated Raman scattering is excited and amplified collectively by both pump laser and stimulated Brillouin scattering.

  20. Driving trajectories in chaotic scattering.

    PubMed

    Macau, Elbert E N; Caldas, Iberê L

    2002-02-01

    In this work we introduce a general approach for targeting in chaotic scattering that can be used to find a transfer trajectory between any two points located inside the scattering region. We show that this method can be used in association with a control of chaos strategy to drive around and keep a particle inside the scattering region. As an illustration of how powerful this approach is, we use it in a case of practical interest in celestial mechanics in which it is desired to control the evolution of two satellites that evolve around a large central body. PMID:11863640

  1. Brillouin scattering at high pressures

    SciTech Connect

    Grimsditch, M.; Polian, A.

    1988-02-01

    Technical advances which have made Brillouin scattering a useful tool in high pressure diamond anvil cell (DAC) studies, viz. multipassing and tandem operation of Fabry-Perot interferometers, are reviewed. Experimental aspects, such as allowed scattering geometries, are outlined and the data analysis required to transform Brillouin spectra into sound velocities and elastic constants is presented. Experimental results on H/sub 2/, N/sub 2/, Ar, and He are presented, and the close relationship between the Brillouin scattering results and equations of state is highlighted.

  2. Geologic Applications of Seismic Scattering

    NASA Astrophysics Data System (ADS)

    Revenaugh, Justin

    Once disregarded as noise, scattered seismic waves are finding increasing application in subsurface imaging. This sea change is driven by the increasing density and quality of seismic recordings and advances in waveform modeling which, together, are allowing seismologists to exploit their unique properties. In addition to extensive application in the energy exploration industry, seismic scattering is now used to characterize heterogeneity in the lower continental crust and subcrustal lithosphere, to examine the relationship between crustal structure and seismogenesis, and to probe the plumbing of active volcanoes. In each application, the study of seismic scattering brings wavelength-scale structure into sharper focus and characterizes the short scale-length fabric of geology.

  3. Driving trajectories in chaotic scattering.

    PubMed

    Macau, Elbert E N; Caldas, Iberê L

    2002-02-01

    In this work we introduce a general approach for targeting in chaotic scattering that can be used to find a transfer trajectory between any two points located inside the scattering region. We show that this method can be used in association with a control of chaos strategy to drive around and keep a particle inside the scattering region. As an illustration of how powerful this approach is, we use it in a case of practical interest in celestial mechanics in which it is desired to control the evolution of two satellites that evolve around a large central body.

  4. Timelike Compton Scattering at Jlab

    SciTech Connect

    Paremuzyan, Rafayel G.

    2014-01-01

    It is demonstrated, that with exclusive final state, data from electron scattering experiments that are recorded with loose trigger requirements can be used to analyze photoproduction reactions. A preliminary results on Timelike Compton Scattering using the electroproduction data from the CLAS detector at Jefferson Lab are presented. In particular, using final state (pe{sup -}e{sup +}) photoproduction of vector mesons and timelike photon is studied. Angular asymmetries in Timelike Compton Scattering region is compared with model predictions in the framework of Generalized Parton Distribution.

  5. Microwave scattering from laser spark in air

    SciTech Connect

    Sawyer, Jordan; Zhang Zhili; Shneider, Mikhail N.

    2012-09-15

    In this paper, microwave Mie scattering from a laser-induced plasma in atmospheric air is computed. It shows that the scattered microwave transitions from coherent Rayleigh scattering to Mie scattering based on the relative transparency of the laser-induced plasma at the microwave frequency. The microwave penetration in the plasma alters from total transparency to partial shielding due to the sharp increase of the electron number density within the avalanche ionization phase. The transition from Rayleigh scattering to Mie scattering is verified by both the temporal evolution of the scattered microwave and the homogeneity of polar scattering plots.

  6. Scattering theory with path integrals

    SciTech Connect

    Rosenfelder, R.

    2014-03-15

    Starting from well-known expressions for the T-matrix and its derivative in standard nonrelativistic potential scattering, I rederive recent path-integral formulations due to Efimov and Barbashov et al. Some new relations follow immediately.

  7. Quantum scattering from cylindrical barriers

    NASA Astrophysics Data System (ADS)

    McAlinden, Sean; Shertzer, Janine

    2016-10-01

    We solve the two-dimensional Schrödinger equation for particles with momentum p x = ℏ k scattering off of a hard circular cylinder using the finite element method; we compare our results with the exact analytic solution. The quantity of interest to experimentalists is the differential cross section σ ( ϕ ) = | f k ( ϕ ) | 2 , which represents the final angular distribution of only the scattered particles. Here, we are also interested in the interference between the incident and scattered wave, which can be seen in the probability density for the total wave function, ρ ( x , y ) = | ψ k ( x , y ) | 2 . We also apply the finite element method to the problem of particles scattering off of a hard rectangular cylinder, for which there is no analytic solution.

  8. Scattered light in photolithographic lenses

    NASA Astrophysics Data System (ADS)

    Kirk, Joseph P.

    1994-05-01

    Scattered light, flare, is present in the images formed by all photolithography lenses and it reduces lithographic process tolerances. It varies from lens to lens and with time, but is easily measured by observation of images of opaque objects formed in positive photoresist. The scattered light halo of a lens is modeled and the model used to estimate the flare for any reticle used with that lens.

  9. Forward glory scattering from bubbles.

    PubMed

    Langley, D S; Marston, P L

    1991-08-20

    The scattering enhancement known as the glory was observed in forward scattering from bubbles in liquids. A physical-optics model of the forward glory is detailed, based on transmitted waves reflected within the bubble. Some aspects of the model are compared with the Mie theory and with features in the cross-polarized light from single bubbles. Clouds of small bubbles rising in water show an angular structure in the forward glory light that is useful for estimating the bubble size.

  10. Polarized lepton-nucleon scattering

    SciTech Connect

    Hughes, E.

    1994-02-01

    Deep inelastic polarized lepton-nucleon scattering is reviewed in three lectures. The first lecture covers the polarized deep inelastic scattering formalism and foundational theoretical work. The second lecture describes the nucleon spin structure function experiments that have been performed up through 1993. The third lecture discusses implication of the results and future experiments aimed at high-precision measurements of the nucleon spin structure functions.

  11. Analytical optical scattering in clouds

    NASA Technical Reports Server (NTRS)

    Phanord, Dieudonne D.

    1989-01-01

    An analytical optical model for scattering of light due to lightning by clouds of different geometry is being developed. The self-consistent approach and the equivalent medium concept of Twersky was used to treat the case corresponding to outside illumination. Thus, the resulting multiple scattering problem is transformed with the knowledge of the bulk parameters, into scattering by a single obstacle in isolation. Based on the size parameter of a typical water droplet as compared to the incident wave length, the problem for the single scatterer equivalent to the distribution of cloud particles can be solved either by Mie or Rayleigh scattering theory. The super computing code of Wiscombe can be used immediately to produce results that can be compared to the Monte Carlo computer simulation for outside incidence. A fairly reasonable inverse approach using the solution of the outside illumination case was proposed to model analytically the situation for point sources located inside the thick optical cloud. Its mathematical details are still being investigated. When finished, it will provide scientists an enhanced capability to study more realistic clouds. For testing purposes, the direct approach to the inside illumination of clouds by lightning is under consideration. Presently, an analytical solution for the cubic cloud will soon be obtained. For cylindrical or spherical clouds, preliminary results are needed for scattering by bounded obstacles above or below a penetrable surface interface.

  12. Scattering in Relativistic Particle Mechanics.

    NASA Astrophysics Data System (ADS)

    de Bievre, Stephan

    The problem of direct interaction in relativistic particle mechanics has been extensively studied and a variety of models has been proposed avoiding the conclusions of the so-called no-interaction theorems. In this thesis we study scattering in the relativistic two-body problem. We use our results to analyse gauge invariance in Hamiltonian constraint models and the uniqueness of the symplectic structure in manifestly covariant relativistic particle mechanics. We first present a general geometric framework that underlies approaches to relativistic particle mechanics. This permits a model-independent and geometric definition of the notions of asymptotic completeness and of Moller and scattering operators. Subsequent analysis of these concepts divides into two parts. First, we study the kinematic properties of the scattering transformation, i.e. those properties that arise solely from the invariance of the theory under the Poincare group. We classify all canonical (symplectic) scattering transformations on the relativistic phase space for two free particles in terms of a single function of the two invariants of the theory. We show how this function is determined by the center of mass time delay and scattering angle and vice versa. The second part of our analysis of the relativistic two-body scattering problem is devoted to the dynamical properties of the scattering process. Hence, we turn to two approaches to relativistic particle mechanics: the Hamiltonian constraint models and the manifestly covariant formalism. Using general geometric arguments, we prove "gauge invariance" of the scattering transformation in the Todorov -Komar Hamiltonian constraint model. We conclude that the scattering cross sections of the Todorov-Komar models have the same angular dependence as their non-relativistic counterpart, irrespective of a choice of gauge. This limits the physical relevance of those models. We present a physically non -trivial Hamiltonian constraint model, starting from

  13. Neutron detector resolution for scattering

    SciTech Connect

    Kolda, S.A.

    1997-03-01

    A resolution function has been determined for scattered neutron experiments at Rensselaer Polytechnic Institute (RPI). This function accounts for the shifting and broadening of the resonance peak due to the additional path length, traveled by the neutron after scattering and prior to detection, along with the broadening of the resonance peak due to the bounce target. This resolution function has been parameterized both in neutron energy and size of the sample disk. Monte Carlo Neutron and Photon (MCNP) modeling has been used to determine the shape of the detector resolution function while assuming that the sample nucleus has an infinite mass. The shape of the function for a monoenergetic neutron point source has been compared to the analytical solution. Additionally, the parameterized detector resolution function has been used to broaden the scatter yield calculated from Evaluated Neutron Data File ENDF/B-VI cross section data for {sup 238}U. The target resolution function has been empirically determined by comparison of the broadened scatter yield and the experimental yield for {sup 238}U. The combined resolution function can be inserted into the SAMMY code to allow resonance analysis for scattering measurements.

  14. Scattering apodizer for laser beams

    DOEpatents

    Summers, M.A.; Hagen, W.F.; Boyd, R.D.

    1984-01-01

    A method is disclosed for apodizing a laser beam to smooth out the production of diffraction peaks due to optical discontinuities in the path of the laser beam, such method comprising introduction of a pattern of scattering elements for reducing the peak intensity in the region of such optical discontinuities, such pattern having smoothly tapering boundaries in which the distribution density of the scattering elements is tapered gradually to produce small gradients in the distribution density, such pattern of scattering elements being effective to reduce and smooth out the diffraction effects which would otherwise be produced. The apodizer pattern may be produced by selectively blasting a surface of a transparent member with fine abrasive particles to produce a multitude of minute pits. In one embodiment, a scattering apodizer pattern is employed to overcome diffraction patterns in a multiple element crystal array for harmonic conversion of a laser beam. The interstices and the supporting grid between the crystal elements are obscured by the gradually tapered apodizer pattern of scattering elements.

  15. Scattering apodizer for laser beams

    DOEpatents

    Summers, Mark A.; Hagen, Wilhelm F.; Boyd, Robert D.

    1985-01-01

    A method is disclosed for apodizing a laser beam to smooth out the production of diffraction peaks due to optical discontinuities in the path of the laser beam, such method comprising introduction of a pattern of scattering elements for reducing the peak intensity in the region of such optical discontinuities, such pattern having smoothly tapering boundaries in which the distribution density of the scattering elements is tapered gradually to produce small gradients in the distribution density, such pattern of scattering elements being effective to reduce and smooth out the diffraction effects which would otherwise be produced. The apodizer pattern may be produced by selectively blasting a surface of a transparent member with fine abrasive particles to produce a multitude of minute pits. In one embodiment, a scattering apodizer pattern is employed to overcome diffraction patterns in a multiple element crystal array for harmonic conversion of a laser beam. The interstices and the supporting grid between the crystal elements are obscured by the gradually tapered apodizer pattern of scattering elements.

  16. Thomson scattering from laser plasmas

    NASA Astrophysics Data System (ADS)

    Glenzer, S. H.; Alley, W. E.; Estabrook, K. G.; de Groot, J. S.; Haines, M. G.; Hammer, J. H.; Jadaud, J.-P.; MacGowan, B. J.; Moody, J. D.; Rozmus, W.; Suter, L. J.; Weiland, T. L.; Williams, E. A.

    1999-05-01

    Thomson scattering has recently been introduced as a fundamental diagnostic of plasma conditions and basic physical processes in dense, inertial confinement fusion plasmas. Experiments at the Nova laser facility [E. M. Campbell et al., Laser Part. Beams 9, 209 (1991)] have demonstrated accurate temporally and spatially resolved characterization of densities, electron temperatures, and average ionization levels by simultaneously observing Thomson scattered light from ion acoustic and electron plasma (Langmuir) fluctuations. In addition, observations of fast and slow ion acoustic waves in two-ion species plasmas have also allowed an independent measurement of the ion temperature. These results have motivated the application of Thomson scattering in closed-geometry inertial confinement fusion hohlraums to benchmark integrated radiation-hydrodynamic modeling of fusion plasmas. For this purpose a high energy 4ω probe laser was implemented recently allowing ultraviolet Thomson scattering at various locations in high-density gas-filled hohlraum plasmas. In particular, the observation of steep electron temperature gradients indicates that electron thermal transport is inhibited in these gas-filled hohlraums. Hydrodynamic calculations which include an exact treatment of large-scale magnetic fields are in agreement with these findings. Moreover, the Thomson scattering data clearly indicate axial stagnation in these hohlraums by showing a fast rise of the ion temperature. Its timing is in good agreement with calculations indicating that the stagnating plasma will not deteriorate the implosion of the fusion capsules in ignition experiments.

  17. Electromagnetic wave scattering by Schwarzschild black holes.

    PubMed

    Crispino, Luís C B; Dolan, Sam R; Oliveira, Ednilton S

    2009-06-12

    We analyze the scattering of a planar monochromatic electromagnetic wave incident upon a Schwarzschild black hole. We obtain accurate numerical results from the partial wave method for the electromagnetic scattering cross section and show that they are in excellent agreement with analytical approximations. The scattering of electromagnetic waves is compared with the scattering of scalar, spinor, and gravitational waves. We present a unified picture of the scattering of all massless fields for the first time. PMID:19658920

  18. Transition of radiative recombination channels from delocalized states to localized states in a GaInP alloy with partial atomic ordering: a direct optical signature of Mott transition?

    NASA Astrophysics Data System (ADS)

    Su, Z. C.; Ning, J. Q.; Deng, Z.; Wang, X. H.; Xu, S. J.; Wang, R. X.; Lu, S. L.; Dong, J. R.; Yang, H.

    2016-03-01

    Anderson localization is a predominant phenomenon in condensed matter and materials physics. In fact, localized and delocalized states often co-exist in one material. They are separated by a boundary called the mobility edge. Mott transition may take place between these two regimes. However, it is widely recognized that an apparent demonstration of Anderson localization or Mott transition is a challenging task. In this article, we present a direct optical observation of a transition of radiative recombination dominant channels from delocalized (i.e., local extended) states to Anderson localized states in the GaInP base layer of a GaInP/GaAs single junction solar cell by the means of the variable-temperature electroluminescence (EL) technique. It is found that by increasing temperature, we can boost a remarkable transition of radiative recombination dominant channels from the delocalized states to the localized states. The delocalized states are induced by the local atomic ordering domains (InP/GaP monolayer superlattices) while the localized states are caused by random distribution of indium (gallium) content. The efficient transfer and thermal redistribution of carriers between the two kinds of electronic states was revealed to result in both a distinct EL mechanism transition and an electrical resistance evolution with temperature. Our study gives rise to a self-consistent precise picture for carrier localization and transfer in a GaInP alloy, which is an extremely technologically important energy material for fabricating high-efficiency photovoltaic devices.

  19. Transition of radiative recombination channels from delocalized states to localized states in a GaInP alloy with partial atomic ordering: a direct optical signature of Mott transition?

    PubMed

    Su, Z C; Ning, J Q; Deng, Z; Wang, X H; Xu, S J; Wang, R X; Lu, S L; Dong, J R; Yang, H

    2016-04-01

    Anderson localization is a predominant phenomenon in condensed matter and materials physics. In fact, localized and delocalized states often co-exist in one material. They are separated by a boundary called the mobility edge. Mott transition may take place between these two regimes. However, it is widely recognized that an apparent demonstration of Anderson localization or Mott transition is a challenging task. In this article, we present a direct optical observation of a transition of radiative recombination dominant channels from delocalized (i.e., local extended) states to Anderson localized states in the GaInP base layer of a GaInP/GaAs single junction solar cell by the means of the variable-temperature electroluminescence (EL) technique. It is found that by increasing temperature, we can boost a remarkable transition of radiative recombination dominant channels from the delocalized states to the localized states. The delocalized states are induced by the local atomic ordering domains (InP/GaP monolayer superlattices) while the localized states are caused by random distribution of indium (gallium) content. The efficient transfer and thermal redistribution of carriers between the two kinds of electronic states was revealed to result in both a distinct EL mechanism transition and an electrical resistance evolution with temperature. Our study gives rise to a self-consistent precise picture for carrier localization and transfer in a GaInP alloy, which is an extremely technologically important energy material for fabricating high-efficiency photovoltaic devices. PMID:26960547

  20. Scattering calculations and confining interactions

    NASA Technical Reports Server (NTRS)

    Buck, Warren W.; Maung, Khin M.

    1993-01-01

    Most of the research work performed under this grant were concerned with strong interaction processes ranging from kaon-nucleon interaction to proton-nucleus scattering calculations. Research performed under this grant can be categorized into three groups: (1) parametrization of fundamental interactions, (2) development of formal theory, and (3) calculations based upon the first two. Parametrizations of certain fundamental interactions, such as kaon-nucleon interaction, for example, were necessary because kaon-nucleon scattering amplitude was needed to perform kaon-nucleus scattering calculations. It was possible to calculate kaon-nucleon amplitudes from the first principle, but it was unnecessary for the purpose of the project. Similar work was also done for example for anti-protons and anti-nuclei. Formal developments to some extent were also pursued so that consistent calculations can be done.

  1. Quantifying entanglement with scattering experiments

    NASA Astrophysics Data System (ADS)

    Marty, O.; Epping, M.; Kampermann, H.; Bruß, D.; Plenio, M. B.; Cramer, M.

    2014-03-01

    We show how the entanglement contained in states of spins arranged on a lattice may be lower bounded with observables arising in scattering experiments. We focus on the partial differential cross section obtained in neutron scattering from magnetic materials but our results are sufficiently general such that they may also be applied to, e.g., optical Bragg scattering from ultracold atoms in optical lattices or from ion chains. We discuss resonating valence bond states and ground and thermal states of experimentally relevant models—such as the Heisenberg, Majumdar-Ghosh, and XY models—in different geometries and with different spin numbers. As a by-product, we find that for the one-dimensional XY model in a transverse field such measurements reveal factorization and the quantum phase transition at zero temperature.

  2. Scattering Polarization in the Chromosphere

    NASA Technical Reports Server (NTRS)

    Keller, C. U.; Sheeley, N. R., Jr.

    1999-01-01

    Scattering polarization from the photosphere observed close to the solar limb has recently become of interest to study turbulent magnetic fields, abundances, and radiative transfer effects. We extend these studies by measuring the scattering polarization off the limb, i.e. in the chromosphere. However, instrumental effects are much more pronounced and more complicated than those affecting on-disk measurements. In particular, scattered light from the telescope mirrors leads to a new type of instrumental polarization that we describe in detail. The differences between the linearly polarized spectra on the disk and off the limb are often very substantial. Here we show the profiles of HeI D(sub 3), the OI triplet at 777 nm, and the Nal D lines. The change in the latter is in reasonable agreement with the recent modeling efforts of atomic polarization in the lower level by Landi Degl'Innocenti (1998).

  3. Critical scattering in polymer melts

    SciTech Connect

    Bates, F.S.; Hartney, M.A.; Wignall, G.D.

    1985-10-01

    Critical phenomena in two classes of polymer melts have been examined by small-angle neutron scattering (SANS); single component block polymers which undergo an order-disorder phase transition, and binary polymer mixtures which exhibit classical liquid-liquid phase separation behavior. A model set of 1,4-polybutadiene-1,2-polybutadiene diblock copolymers containing perdeuterated 1,4-polybutadiene blocks were investigated by SANS in the disordered state. The SANS spectra exhibit a peak in the scattering intensity which diverges at the ordering transition, in close agreement with mean-field theory. Binary blends of perdeuterated and protonated 1,4-polybutadiene homopolymers have been found to form regular solutions characterized by an upper critical solution temperature (UCST). Near the critical point, these mixtures exhibit classical critical scattering as measured by SANS. The second set of results raises serious questions regarding the widely held assumption that deuterated and protonated polymers form ideal mixtures.

  4. Compton scattering and generalized polarizabilities

    SciTech Connect

    Scherer, S.

    2005-05-06

    In recent years, real and virtual Compton scattering off the nucleon have attracted considerable interest from both the experimental and theoretical sides. Real Compton scattering gives access to the so-called electromagnetic polarizabilities containing the structure information beyond the global properties of the nucleon such as its charge, mass, and magnetic moment. These polarizabilities have an intuitive interpretation in terms of induced dipole moments and thus characterize the response of the constituents of the nucleon to a soft external stimulus. The virtual Compton scattering reaction e- p {yields} e- p{gamma} allows one to map out the local response to external fields and can be described in terms of generalized electromagnetic polarizabilities. A simple classical interpretation in terms of the induced electric and magnetic polarization densities is proposed. We will discuss experimental results for the polarizabilities of the proton and compare them with theoretical predictions.

  5. Theory of waves incoherently scattered

    NASA Technical Reports Server (NTRS)

    Bauer, P.

    1974-01-01

    Electromagnetic waves impinging upon a plasma at frequencies larger than the plasma frequency, suffer weak scattering. The scattering arises from the existence of electron density fluctuations. The received signal corresponds to a particular spatial Fourier component of the fluctuations, the wave vector of which is a function of the wavelength of the radiowave. Wavelengths short with respect to the Debye length of the medium relate to fluctuations due to non-interacting Maxwellian electrons, while larger wavelengths relate to fluctuations due to collective Coulomb interactions. In the latter case, the scattered signal exhibits a spectral distribution which is characteristic of the main properties of the electron and ion gases and, therefore, provides a powerful diagnosis of the state of the ionosphere.

  6. Nuclear Scattering from Transition Metals

    NASA Astrophysics Data System (ADS)

    Hira, Ajit; McKeough, James; Valerio, Mario; Cathey, Tommy

    2016-03-01

    In view of the continued interest in the scattering of light projectiles by metallic nuclei, we present a computational study of the interactions between different nuclear species of atoms such as H through F (Z <= 9) and the nuclei of Silver, Palladium and other metals. Recent work has shown that neutron scattering can be used to record holographic images of materials. We have developed a FORTRAN computer program to compute stopping cross sections and scattering angles in Ag and other metals for the small nuclear projectiles, using Monte Carlo calculation. This code allows for different angles of incidence. Next, simulations were done in the energy interval from 50 to 210 keV. The computational results thus obtained are compared with relevant experimental data. The data are further analyzed to identify periodic trends in terms of the atomic number of the projectile. Such studies also have potential applications in nuclear physics and in nuclear medicine. Funding from National Science Foundation.

  7. Light Scattering in Exoplanet Transits

    NASA Astrophysics Data System (ADS)

    Robinson, Tyler D.; Fortney, Jonathan J.

    2016-10-01

    Transit spectroscopy is currently the leading technique for studying exoplanet atmospheric composition, and has led to the detection of molecular species, clouds, and/or hazes for numerous worlds outside the Solar System. The field of exoplanet transit spectroscopy will be revolutionized with the anticipated launch of NASA's James Webb Space Telescope (JWST) in 2018. Over the course of the design five year mission for JWST, the observatory is expected to provide in-depth observations of many tens of transiting exoplanets, including some worlds in the poorly understood 2–4 Earth-mass regime. As the quality of transit spectrum observations continues to improve, so should models of exoplanet transits. Thus, certain processes initially thought to be of second-order importance should be revisited and possibly added to modeling tools. For example, atmospheric refraction, which was commonly omitted from early transit spectrum models, has recently been shown to be of critical importance in some terrestrial exoplanet transits. Beyond refraction, another process that has seen little study with regards to exoplanet transits is light multiple scattering. In most cases, scattering opacity in exoplanet transits has been treated as equivalent to absorption opacity. However, this equivalence cannot always hold, such as in the case of a strongly forward scattering, weakly absorbing aerosol. In this presentation, we outline a theory of exoplanet transit spectroscopy that spans the geometric limit (used in most modern models) to a fully multiple scattering approach. We discuss a new technique for improving model efficiency that effectively separates photon paths, which tend to vary slowly in wavelength, from photon absorption, which can vary rapidly in wavelength. Using this newly developed approach, we explore situations where cloud or haze scattering may be important to JWST observations of gas giants, and comment on the conditions necessary for scattering to become a major

  8. Nonlinear scattering in gold nanospheres

    NASA Astrophysics Data System (ADS)

    Shen, Po-Ting; Lin, Cheng-Wei; Liu, Hsiang-Lin; Chu, Shi-Wei

    2016-03-01

    Nonlinearity enhanced by noble metallic nanoparticles provide novel light manipulation capabilities and innovative applications. Recently, we discovered a new nonlinear phenomenon on the scattering of metallic nanoparticles by continuous-wave (CW) lasers at the intensity around MW/cm2 and applied to super-resolution microscopy that allowed spatial resolution of plasmonic nanostructures down to λ/8. However, its mechanism is still unknown. In this work, we elaborate the mechanism behind the nonlinear scattering of gold nanospheres. There are four possible candidates: intraband transition, interband transition, hot electron, and hot lattice. Each of them has a corresponding nonlinear refractive index (n2), which is related to temporal dependence of its light-matter interaction. We first measure the intensity dependence of nonlinear scattering to extract the effective n2 value. We find out it has the closest n2 value to hot lattice, which causes either the shift or weakening of the surface plasmon resonance (SPR). To further verify the mechanism, the nanospheres are heated up with both a hot plate and a CW laser, and the variation of single-particle SPR scattering spectra are measured. In both cases, more than 50% reduction of scattering is observed, when temperature rises a few tens of degrees or when illumination intensity reaches the order of 1MW/cm2. Thus, we conclude the spectra variation by the two different heating source, as well as the nonlinear scattering are all due to hot lattice, and subsequent permittivity change with temperature. The innovative concept of hot lattice plasmonics not only opens up a new dimension for nonlinear plasmonics, but also predicts the potential of similar nonlinearity in other materials as long as their permittivity changes with temperature.

  9. Stimulated Brillouin Scattering Microscopic Imaging

    PubMed Central

    Ballmann, Charles W.; Thompson, Jonathan V.; Traverso, Andrew J.; Meng, Zhaokai; Scully, Marlan O.; Yakovlev, Vladislav V.

    2015-01-01

    Two-dimensional stimulated Brillouin scattering microscopy is demonstrated for the first time using low power continuous-wave lasers tunable around 780 nm. Spontaneous Brillouin spectroscopy has much potential for probing viscoelastic properties remotely and non-invasively on a microscopic scale. Nonlinear Brillouin scattering spectroscopy and microscopy may provide a way to tremendously accelerate the data aquisition and improve spatial resolution. This general imaging setup can be easily adapted for specific applications in biology and material science. The low power and optical wavelengths in the water transparency window used in this setup provide a powerful bioimaging technique for probing the mechanical properties of hard and soft tissue. PMID:26691398

  10. Neutron scattering: Progress and prospects

    SciTech Connect

    Axe, J.D. )

    1991-05-10

    Over the last decade the unique properties of neutrons have proven useful in a growing number of scientific disciplines. Neutron scattering, traditionally the probe of choice for many magnetic and spectroscopic studies, is now firmly established as an invaluable complement to x-ray scattering for structural and dynamic studies within many other areas of the material sciences, chemistry, and biology. In recent years the instruments and techniques have matured to the point where they are of increasing relevance to the understanding and design of improved practical, everyday materials.

  11. Stimulated Brillouin Scattering Microscopic Imaging.

    PubMed

    Ballmann, Charles W; Thompson, Jonathan V; Traverso, Andrew J; Meng, Zhaokai; Scully, Marlan O; Yakovlev, Vladislav V

    2015-01-01

    Two-dimensional stimulated Brillouin scattering microscopy is demonstrated for the first time using low power continuous-wave lasers tunable around 780 nm. Spontaneous Brillouin spectroscopy has much potential for probing viscoelastic properties remotely and non-invasively on a microscopic scale. Nonlinear Brillouin scattering spectroscopy and microscopy may provide a way to tremendously accelerate the data aquisition and improve spatial resolution. This general imaging setup can be easily adapted for specific applications in biology and material science. The low power and optical wavelengths in the water transparency window used in this setup provide a powerful bioimaging technique for probing the mechanical properties of hard and soft tissue.

  12. Stimulated Brillouin Scattering Microscopic Imaging

    NASA Astrophysics Data System (ADS)

    Ballmann, Charles W.; Thompson, Jonathan V.; Traverso, Andrew J.; Meng, Zhaokai; Scully, Marlan O.; Yakovlev, Vladislav V.

    2015-12-01

    Two-dimensional stimulated Brillouin scattering microscopy is demonstrated for the first time using low power continuous-wave lasers tunable around 780 nm. Spontaneous Brillouin spectroscopy has much potential for probing viscoelastic properties remotely and non-invasively on a microscopic scale. Nonlinear Brillouin scattering spectroscopy and microscopy may provide a way to tremendously accelerate the data aquisition and improve spatial resolution. This general imaging setup can be easily adapted for specific applications in biology and material science. The low power and optical wavelengths in the water transparency window used in this setup provide a powerful bioimaging technique for probing the mechanical properties of hard and soft tissue.

  13. MOTT PROGRAM SUMMARIES (TITLE SUPPLIED).

    ERIC Educational Resources Information Center

    Flint Board of Education, MI.

    THE BETTER TOMORROW FOR THE URBAN CHILD PROGRAM (BTU) ATTEMPTS TO HELP INNER-CITY CHILDREN BECOME MORE EFFECTIVE CITIZENS, BOTH EDUCATIONALLY AND SOCIALLY, THROUGH THE USE OF ADDITIONAL HUMAN AND MATERIAL RESOURCES. THE GOALS ARE TO RAISE THE LEVEL OF SCHOOL READINESS, TO DEVELOP A GREATER MOTIVATION FOR LEARNING, AND TO IMPROVE STUDENT SELF-IMAGE…

  14. The Full Mottness: Asymptiotic Slavery

    SciTech Connect

    Phillips, Philip

    2004-03-10

    Vast progress in theoretical solid state physics has been made by constructing models which mimic the low-energy properties of solids. Essential to the success of this program is the separability of the high and low energy degrees of freedom. While it is hoped that a high energy reduction can be made to solve the problem of high temperature superconductivity in the copper oxide materials, I will show that no consistent theory is possible if the high energy scale is removed. At the heart of the problem is the mixing of all energy scales (that is, UV-IR mixing) in the copper-oxide materials. Several optical measurements will be discussed which demonstrate the slavery of high and low energy degrees of freedom. The implications of asymptotic slavery for the phase diagram of the cuprates will be discussed.

  15. Pauli Principle and Pion Scattering

    DOE R&D Accomplishments Database

    Bethe, H. A.

    1972-10-01

    It is pointed out that if the Pauli principle is taken into account in the discussion of pion scattering by complex nuclei (as it ought, of course, to be) some rather implausible consequences of some earlier treatments of this problem can be avoided. (auth)

  16. Elastic forward scattering of gluons

    NASA Astrophysics Data System (ADS)

    Ermolaev, B. I.

    1995-06-01

    The colour octet and singlet parts of the elastic gg→ gg-scattering amplitude are evaluated in the Regge kinematical region s≫- t in the LLA, with iπ-terms taken into account, by constructing and solving a set of the infrared evolution equations.

  17. Light Scattering by Nonspherical Particles

    NASA Technical Reports Server (NTRS)

    Mishchenko, Michael I.; Travis, Larry D.; Hovenier, Joop W.

    1998-01-01

    Improved understanding of electromagnetic scattering by nonspherical particles is important to many science and engineering disciplines and was the subject of the Conference on Light Scattering by Nonspherical Particles: Theory, Measurements, and Applications. The conference was held 29 September-1 October 1998 at the Goddard Institute for Space Studies in New York City and brought together 115 participants from 18 countries. The main objective of the conference was to highlight and summarize the rapid advancements in the field, including numerical methods for computing the single and multiple scattering of electromagnetic radiation by nonspherical and heterogeneous particles, measurement approaches, knowledge of characteristic features in scattering patterns, retrieval and remote sensing techniques, nonspherical particle sizing, and various practical applications. The conference consisted of twelve oral and one poster sessions. The presentations were loosely grouped based on broad topical categories. In each of these categories invited review talks highlighted and summarized specific active areas of research. To ensure a high-quality conference, all abstracts submitted had been reviewed by members of the Scientific Organizing Committee for technical merit and content. The conference program was published in the June 1998 issue of the Bulletin of the American Meteorological Society and is available on the World Wide Web at http://www.giss.nasa.gov/-crmim/conference/program.html. Authors of accepted papers and review presentations contributed to a volume of preprints published by the American Meteorological Society' and distributed to participants at the conference.

  18. Full potential multiple scattering theory

    SciTech Connect

    MacLaren, J.M.

    1994-10-20

    A practical method for performing self-consistent electronic structure calculations based upon full-potential multiple-scattering theory is presented. Solutions to the single site Schroedinger equation are obtained by solving coupled channel integral equations for a potential which is analytically continued out to the circumscribing sphere. This potential coincides with the full cell potential inside each atomic cell. Scattering matrices and wavefunctions for the full cell potential are obtained from surface Wronskian relations. The charge density is obtained from the single particle Green`s function. This Green`s function is computed using the cell scattering matrices and wavefunctions using the layer multiple scattering theory. Self consistent solutions require a solution at each iteration to the Poisson equation. The Poisson equation is solved using a variational cellular method. In the approach a local solution to each cell is augmented by adding a series of regular harmonics (solutions to Laplace`s equation). Minimizing the coulomb energy, subject to continuity of the potential across all cell boundary provides an expression for the coefficients of the regular harmonics. This method is applied to BCC Nb. Calculated properties converge well in angular momentum and show comparable accuracy to full potential linearized muffin-tin orbital calculations.

  19. Intrabeam scattering in the HEB

    SciTech Connect

    Larson, D.J.

    1994-03-01

    A study of Intrabeam Scattering (IBS) in the High Energy Booster (HEB) is presented. Piwinski`s formulas for IBS are presented and evaluated for the HEB. A computer code written to evaluate Piwinski`s formulas is discussed. The result of the study is that IBS should not be a problem for the HEB, although the safety factor is not enormous.

  20. Interferometric Rayleigh Scattering Measurement System

    NASA Technical Reports Server (NTRS)

    Bivolaru, Daniel (Inventor); Danehy, Paul M. (Inventor); Lee, Joseph W. (Inventor)

    2008-01-01

    A method and apparatus for performing simultaneous multi-point measurements of multiple velocity components in a gas flow is described. Pulses of laser light are directed to a measurement region of unseeded gas to produce Rayleigh or Mie scattered light in a plurality of directions. The Rayleigh or Mie scattered light is collected from multiple directions and combined in a single collimated light beam. The Rayleigh or Mie scattered light is then mixed together with a reference laser light before it is passed through a single planar Fabry-Perot interferometer for spectral analysis. At the output of the interferometer, a high-sensitivity CCD camera images the interference fringe pattern. This pattern contains the spectral and spatial information from both the Rayleigh scattered light and the reference laser light. Interferogram processing software extracts and analyzes spectral profiles to determine the velocity components of the gas flow at multiple points in the measurement region. The Rayleigh light rejected by the interferometer is recirculated to increase the accuracy and the applicability of the method for measurements at high temperatures without requiring an increase in the laser energy.

  1. On the spatial bandwidth of scattered fields

    NASA Astrophysics Data System (ADS)

    Bucci, Ovidio M.; Franceschetti, Giorgio

    1987-12-01

    The concept of spatial bandwidth of scattered electromagnetic fields is introduced. It is shown that the scattered fields are almost space-bandlimited functions. The effective bandwidth W is introduced and evaluated for a very general scattering system, as well as the error made using functions bandlimited to values greater than the effective bandwidth (w greater than W) for representing the scattered field. The effective bandwidth is very simply related to the maximum dimension of the scattering system; the error drops to negligible values for modest increases of w compared to W, in the case of large scatterers. Consequences of these general results are stressed.

  2. Scattering by anisotropic grains in beryllium mirrors

    SciTech Connect

    Church, E.L. ); Takacs, P.Z. ); Stover, J.C. )

    1990-08-01

    Scattering from mirror surfaces arises from topographic and non-topographic sources. This paper considers the nontopographic scattering of beryllium mirrors modelled as a collection of randomly oriented bireflective grains. Simple scattering theory shows that this type of scatting scales as {lambda}{sup {minus}2}, rather than as {lambda}{sup {minus}4} for topographic scattering, which means that it is relatively more important at long radiation wavelengths. Estimates of the intensity based an available short-wavelength values of the anisotropic optical constants of beryllium indicate that this type of scattering could dominate the topographic scattering from smooth surfaces at CO{sub 2} wavelengths. 10 refs., 2 figs.

  3. Axisymmetric scattering of scalar waves by spheroids.

    PubMed

    Lekner, John; Boyack, Rufus

    2011-06-01

    A phase shift formulation of scattering by oblate and prolate spheroids is presented, in parallel with the partial-wave theory of scattering by spherical obstacles. The crucial step is application of a finite Legendre transform to the Helmholtz equation in spheroidal coordinates. In the long-wavelength limit the spheroidal analog of the spherical scattering length immediately gives the cross section. Analytical results are readily obtained for scattering of Schrödinger particle waves by impenetrable spheroids, and for scattering of sound waves by acoustically soft spheroidal objects. The method is restricted to scattering by spheroids whose symmetry axis is coincident with the direction of the incident plane wave. PMID:21682372

  4. Alpha particle collective Thomson scattering in TFTR

    SciTech Connect

    Machuzak, J.S.; Woskov, P.P.; Rhee, D.Y.; Gilmore, J.; Bretz, N.L.; Park, H.K.; Aamodt, R.E.; Cheung, P.Y.; Russell, D.A.; Bindslev, H.

    1993-11-01

    A collective Thomson scattering diagnostic is being implemented on TFTR to measure alpha particle, energetic and thermal ion densities and velocity distributions. A 60 GHz, 0.1-1 kW gyrotron will be used as the transmitter source, and the scattering geometry will be perpendicular to the magnetic field in the extraordinary mode polarization. An enhanced scattered signal is anticipated from fluctuations in the lower hybrid frequency range with this scattering geometry. Millimeter wave collective Thomson scattering diagnostics have the advantage of larger scattering angles to decrease the amount of stray light, and long, high power, modulated pulses to obtain improved signal to noise through synchronous detection techniques.

  5. Axisymmetric scattering of scalar waves by spheroids.

    PubMed

    Lekner, John; Boyack, Rufus

    2011-06-01

    A phase shift formulation of scattering by oblate and prolate spheroids is presented, in parallel with the partial-wave theory of scattering by spherical obstacles. The crucial step is application of a finite Legendre transform to the Helmholtz equation in spheroidal coordinates. In the long-wavelength limit the spheroidal analog of the spherical scattering length immediately gives the cross section. Analytical results are readily obtained for scattering of Schrödinger particle waves by impenetrable spheroids, and for scattering of sound waves by acoustically soft spheroidal objects. The method is restricted to scattering by spheroids whose symmetry axis is coincident with the direction of the incident plane wave.

  6. Iterative scatter correction based on artifact assessment

    NASA Astrophysics Data System (ADS)

    Wiegert, Jens; Hohmann, Steffen; Bertram, Matthias

    2008-03-01

    In this paper we propose a novel scatter correction methodology for X-ray based cone-beam CT that allows to combine the advantages of projection-based and volume-based correction approaches. The basic idea is to use a potentially non-optimal projection-based scatter correction method and to iteratively optimize its performance by repeatedly assessing remaining scatter-induced artifacts in intermediately reconstructed volumes. The novel approach exploits the fact that due to the flatness of the scatter-background, compensation itself is most easily performed in the projection-domain, while the scatter-induced artifacts can be better observed in the reconstructed volume. The presented method foresees to evaluate the scatter correction efficiency after each iteration by means of a quantitative measure characterizing the amount of residual cupping and to adjust the parameters of the projection-based scatter correction for the next iteration accordingly. The potential of this iterative scatter correction approach is demonstrated using voxelized Monte Carlo scatter simulations as ground truth. Using the proposed iterative scatter correction method, remarkable scatter correction performance was achieved both using simple parametric heuristic techniques as well as by optimizing previously published scatter estimation schemes. For the human head, scatter induced artifacts were reduced from initially 148 HU to less than 8.1 HU to 9.1 HU for different studied methods, corresponding to an artifact reduction exceeding 93%.

  7. 2004 Photon Correlation and Scattering Conference

    NASA Technical Reports Server (NTRS)

    Meyer, William (Editor); Smart, Anthony (Editor); Wegdam, Gerard (Editor); Dogariu, Aristide (Editor); Carpenter, Bradley (Editor)

    2004-01-01

    The Photon Correlation and Scattering (PCS) meeting welcomes all who are interested in the art and science of photon correlation and its application to optical scattering. The meeting is intended to enhance interactions between theory, applications, instrument design, and participants.

  8. Surface wave dispersion from small vertical scatterers

    NASA Astrophysics Data System (ADS)

    van Wijk, K.; Levshin, A. L.

    2004-10-01

    Heterogeneity in the subsurface creates conflicting types of dispersion of seismic waves. A laboratory and numerical experiment show that multiple scattering of elastic waves from isolated heterogeneities near the surface not only attenuates, but also delays coherent events. Because scattering off these impedance contrasts is frequency dependent, multiple scattering is a source of dispersion. If ignored, multiple scattering dispersion could be erroneously attributed to a model with horizontal homogeneous layers of different wave speeds.

  9. Nonstationary interference and scattering from random media

    SciTech Connect

    Nazikian, R.

    1991-12-01

    For the small angle scattering of coherent plane waves from inhomogeneous random media, the three dimensional mean square distribution of random fluctuations may be recovered from the interferometric detection of the nonstationary modulational structure of the scattered field. Modulational properties of coherent waves scattered from random media are related to nonlocal correlations in the double sideband structure of the Fourier transform of the scattering potential. Such correlations may be expressed in terms of a suitability generalized spectral coherence function for analytic fields.

  10. Electromagnetic wave scattering by an external field

    NASA Astrophysics Data System (ADS)

    Sannikov, S. S.

    1995-08-01

    The quantum electrodynamics of bilocal fields is used to calculate the triangular Feynman diagrams describing the elastic scattering of a classical electromagnetic wave by an external Coulomb field. The total contribution of the diagrams is nonzero because of the violation of both the Furry theorem (CP or T symmetries) and the Ward identities. The cross section for this scattering process is found for low and high energies. A comparison with Compton scattering and Euler—Heisenberg scattering is given.

  11. Brillouin scattering self-cancellation.

    PubMed

    Florez, O; Jarschel, P F; Espinel, Y A V; Cordeiro, C M B; Mayer Alegre, T P; Wiederhecker, G S; Dainese, P

    2016-01-01

    The interaction between light and acoustic phonons is strongly modified in sub-wavelength confinement, and has led to the demonstration and control of Brillouin scattering in photonic structures such as nano-scale optical waveguides and cavities. Besides the small optical mode volume, two physical mechanisms come into play simultaneously: a volume effect caused by the strain-induced refractive index perturbation (known as photo-elasticity), and a surface effect caused by the shift of the optical boundaries due to mechanical vibrations. As a result, proper material and structure engineering allows one to control each contribution individually. Here, we experimentally demonstrate the perfect cancellation of Brillouin scattering arising from Rayleigh acoustic waves by engineering a silica nanowire with exactly opposing photo-elastic and moving-boundary effects. This demonstration provides clear experimental evidence that the interplay between the two mechanisms is a promising tool to precisely control the photon-phonon interaction, enhancing or suppressing it. PMID:27283092

  12. Positron scattering from vinyl acetate

    NASA Astrophysics Data System (ADS)

    Chiari, L.; Zecca, A.; Blanco, F.; García, G.; Brunger, M. J.

    2014-09-01

    Using a Beer-Lambert attenuation approach, we report measured total cross sections (TCSs) for positron scattering from vinyl acetate (C4H6O2) in the incident positron energy range 0.15-50 eV. In addition, we also report an independent atom model with screening corrected additivity rule computation results for the TCSs, differential and integral elastic cross sections, the positronium formation cross section and inelastic integral cross sections. The energy range of these calculations is 1-1000 eV. While there is a reasonable qualitative correspondence between measurement and calculation for the TCSs, in terms of the energy dependence of those cross sections, the theory was found to be a factor of ˜2 larger in magnitude at the lower energies, even after the measured data were corrected for the forward angle scattering effect.

  13. Brillouin scattering self-cancellation

    NASA Astrophysics Data System (ADS)

    Florez, O.; Jarschel, P. F.; Espinel, Y. A. V.; Cordeiro, C. M. B.; Mayer Alegre, T. P.; Wiederhecker, G. S.; Dainese, P.

    2016-06-01

    The interaction between light and acoustic phonons is strongly modified in sub-wavelength confinement, and has led to the demonstration and control of Brillouin scattering in photonic structures such as nano-scale optical waveguides and cavities. Besides the small optical mode volume, two physical mechanisms come into play simultaneously: a volume effect caused by the strain-induced refractive index perturbation (known as photo-elasticity), and a surface effect caused by the shift of the optical boundaries due to mechanical vibrations. As a result, proper material and structure engineering allows one to control each contribution individually. Here, we experimentally demonstrate the perfect cancellation of Brillouin scattering arising from Rayleigh acoustic waves by engineering a silica nanowire with exactly opposing photo-elastic and moving-boundary effects. This demonstration provides clear experimental evidence that the interplay between the two mechanisms is a promising tool to precisely control the photon-phonon interaction, enhancing or suppressing it.

  14. Brillouin scattering self-cancellation

    PubMed Central

    Florez, O.; Jarschel, P. F.; Espinel, Y. A. V.; Cordeiro, C. M. B.; Mayer Alegre, T. P.; Wiederhecker, G. S.; Dainese, P.

    2016-01-01

    The interaction between light and acoustic phonons is strongly modified in sub-wavelength confinement, and has led to the demonstration and control of Brillouin scattering in photonic structures such as nano-scale optical waveguides and cavities. Besides the small optical mode volume, two physical mechanisms come into play simultaneously: a volume effect caused by the strain-induced refractive index perturbation (known as photo-elasticity), and a surface effect caused by the shift of the optical boundaries due to mechanical vibrations. As a result, proper material and structure engineering allows one to control each contribution individually. Here, we experimentally demonstrate the perfect cancellation of Brillouin scattering arising from Rayleigh acoustic waves by engineering a silica nanowire with exactly opposing photo-elastic and moving-boundary effects. This demonstration provides clear experimental evidence that the interplay between the two mechanisms is a promising tool to precisely control the photon–phonon interaction, enhancing or suppressing it. PMID:27283092

  15. Advanced studies of electromagnetic scattering

    NASA Technical Reports Server (NTRS)

    Ling, Hao

    1994-01-01

    In radar signature applications it is often desirable to generate the range profiles and inverse synthetic aperture radar (ISAR) images of a target. They can be used either as identification tools to distinguish and classify the target from a collection of possible targets, or as diagnostic/design tools to pinpoint the key scattering centers on the target. The simulation of synthetic range profiles and ISAR images is usually a time intensive task and computation time is of prime importance. Our research has been focused on the development of fast simulation algorithms for range profiles and ISAR images using the shooting and bouncing ray (SBR) method, a high frequency electromagnetic simulation technique for predicting the radar returns from realistic aerospace vehicles and the scattering by complex media.

  16. Thermal neutron scattering in graphite

    NASA Astrophysics Data System (ADS)

    Al-Qasir, Iyad Ibrahim

    Generation IV Very High Temperature Reactor (VHTR) concepts, are graphite moderated and gas cooled thermal spectrum reactors. The characteristics of the low energy (E < 1 eV) neutron spectrum in these reactors will be dictated by the process of neutron slowing-down and thermalization in the graphite moderator. The ability to accurately predict this process in these reactors can have significant neutronic and safety implications. In reactor design calculations, thermal neutron scattering cross section libraries are needed for the prediction of the thermal neutron environment in the core. Currently used libraries (ENDF/B-VII) are a product of the 1960s and remain based on many physical approximations. In addition, these libraries show noticeable discrepancies with experimental data. In this work, investigation of thermal neutron scattering in graphite as a function of temperature was performed. The fundamental input for the calculation of thermal neutron scattering cross sections, i.e., the phonon frequency distribution and/or the dispersion relations, was generated using a modern approach that is based on quantum mechanical electronic structure (ab initio) simulations combined with a lattice dynamics direct method supercell approach. The calculations were performed using the VASP and PHONON codes. The VASP calculations used the local density approximation, and the projector augmented-wave pseudopotential. A supercell of 144 atoms was used; and the integration over the Brillouin zone was confined to a 3x3x4 k-mesh generated by the Monkhorst-Pack scheme. A plane-wave basis set with an energy cutoff of 500 eV was applied. The corresponding dispersion relations, heat capacity, and phonon frequency distribution show excellent agreement with experimental data. Despite the use of the above techniques to produce more accurate input data, the examination of the results indicated persistence of the inconsistencies between calculations and measurements at neutron energies

  17. Stochastic approximation to multiple scattering in clouds.

    PubMed

    Zahavi, E

    1979-05-15

    The problem of multiple radiation scattering in a 3-D cloud is considered. The radiation is considered as energy bundles that impinge on the cloud's particles and are scattered around. The probabilistic expressions for bundle distribution are developed. An expression for radiation diffusivity for the nonisotropic scatter is presented. Two numerical examples show the application of the present theory.

  18. Neutron Scattering Studies of Cement

    NASA Astrophysics Data System (ADS)

    Allen, Andrew

    2010-03-01

    Despite more than a century of research, basic questions remain regarding both the internal structure and the role of water in Ordinary Portland cement (OPC) concrete, the world's most widely used manufactured material. Most such questions concern the primary hydration product and strength-building phase of OPC paste, the calcium silicate hydrate (C-S-H) gel. When cement and water are mixed, this phase precipitates as clusters of nanoscale (nearly amorphous) colloidal particles with an associated water-filled inter-particle pore system. Most attempts to characterize the C-S-H gel and the behavior of the associated water involve drying or other processes that, themselves, change the bound water content within and around the gel. Neutron scattering methods do not suffer from this disadvantage. Furthermore, the neutron isotope effect and the neutron's sensitivity to molecular motion have enabled considerable progress to be made in recent years by: (i) determining the C-S-H composition, density and gel structure in small-angle neutron scattering (SANS) H/D contrast variation studies; (ii) elucidating the changing state of water within cement as hydration progresses using quasielastic neutron scattering (QENS); and (iii) measuring the production and consumption of nanoscale calcium hydroxide (CH), a by-product of cement hydration that co-exists with the C-S-H gel, using inelastic neutron scattering (INS). These experiments have provided new insights into the physics and chemistry of cement hydration, and have implications for the design of new concretes with pozzolanic cement additions that are intended to address environmental concerns and sustainability issues.

  19. Spectroscopy, scattering, and KK molecules

    SciTech Connect

    Weinstein, J.

    1994-04-01

    The author presents a pedagogical description of a new theoretical technique, based on the multichannel Schroedinger equation, for simultaneously applying the quark model to both meson spectroscopy and meson-meson scattering. This is an extension of an earlier analysis which led to the prediction that the f{sub o}(975) and a{sub o}(980) scalar mesons are K{bar K} molecular states.

  20. Parity Violation in Electron Scattering

    SciTech Connect

    Beise, Elizabeth

    2007-10-26

    About thirty years ago, electron scattering from nucleons was used [1] to identify, and then measure, the properties of the weak interaction, the only force of nature known to violate the symmetry parity. The basic technique has not fundamentally changed, which is to look for a small asymmetry in count rate from scattering a polarized electron beam from an unpolarized target. Since then, parity-violating (PV) electron scattering has developed substantially, a result of significant improvements in polarized electron beams, accelerator advancements, and developments in cryogenic targets that make it possible to carry out experiments with much higher statistical precision. In the last decade PV experiments have focused on using the complementary electron-quark flavor coupling of the weak interaction to identify and place limits on contributions of strange quark-antiquark pairs to the charge and magnetism of the proton. This observable provides a unique window into the structure of the proton since strange quark contributions can arise only from the sea of quarks and gluons that are responsible for the vast majority of the nucleon's mass. This paper will report on recent results aimed at this goal, along with a brief overview of future directions.