Bulletin of the American Physical Society
APS March Meeting 2011
Volume 56, Number 1
Monday–Friday, March 21–25, 2011; Dallas, Texas
Session W18: Many Body |
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Sponsoring Units: DCOMP Chair: Munehisa Matsumoto, University of California, Davis Room: D172 |
Thursday, March 24, 2011 11:15AM - 11:27AM |
W18.00001: Exact asymptotes of static and dynamic correlation functions of the 1D Bose gas Aditya Shashi, Leonid Glazman, Jean-Sebastien Caux, Adilet Imambekov Recent experiments with ultracold atomic gases have provided realizations of one-dimensional systems of bosons with contact interactions, described by the Lieb-Liniger model. These experiments have revived interest in the correlation functions for this model. Since a fully analytical calculation of the correlation functions is still lacking, our results [1] represent a significant step forward. We have combined field theoretical approaches with an analysis of the finite size scaling of exact form factors of the Lieb-Liniger model to analytically calculate ``non-universal'' prefactors in the long-distance behavior of correlation functions as well as prefactors of singularities in dynamic response functions such as the density structure factor and spectral function. We have also proved the existence of singularities within a continuum spectrum. \\[4pt] [1] A. Shashi, L. I. Glazman, J-S. Caux and A. Imambekov, arXiv:1010.2268. [Preview Abstract] |
Thursday, March 24, 2011 11:27AM - 11:39AM |
W18.00002: Correlation functions of nonlinear Luttinger liquids as Fredholm determinants Yinbin Ma, Adilet Imambekov One dimensional quantum liquids are often described within an effective linear hydrodynamic approach known as Luttinger liquid theory. As the principal simplification, a generic spectrum of the constituent particles is replaced by a linear one, which leads to a linear hydrodynamic theory. It has been shown recently [1] that the nonlinearity of the generic spectrum leads to a significant modification of the dynamic response functions. Their description can be achieved within the universal framework of nonlinear Luttinger liquid theory. We show here that correlation functions within such approach can be expressed as Fredholm determinants, and evaluate them in low energy regions for arbitrary interaction strength and small temperatures. \\[4pt] [1] ``Universal theory of nonlinear Luttinger liquids,'' A. Imambekov and L.I. Glazman, Science 323, 228 (2009) [Preview Abstract] |
Thursday, March 24, 2011 11:39AM - 11:51AM |
W18.00003: Ab initio Low-Dimensional Physics Opened Up by Constrained RPA for Energy and Space: Applications to LaFeAsO and $\kappa $-(BEDT-TTF)$_{2}$X Kazuma Nakamura, Yoshihide Yoshimoto, Yoshiro Nohara, Masatoshi Imada Studies on outstanding electron correlation effects such as non-Fermi liquid behavior and unconventional superconductivity discovered in systems with low-dimensional anisotropy have continuously been at a front of condensed matter physics. Analyses for 1D or 2D simplified models have played a primary role in understanding essence of correlation effects, but to a large extent, the studies rely on ad hoc adjustable parameters as in the Hubbard models. We develop a new ab initio downfolding scheme for deriving effective low-energy models with low spatial dimensions [1]. The scheme is based on constrained random-phase-approximations by imposing constraints not only in ``energy'' but also in ``space''. We show real applications for 2D-layered superconductors of LaFeAsO and $\kappa $-(BEDT-TTF)$_{2}$X. The derived interactions in the effective models become short ranged essentially within up to next-nearest neighbors and thus justify multiband 2D Hubbard models as effective models for these materials from first principles. This work is supported from MEXT Japan under grant numbers 22740215 and 22104010.\\[0pt] [1] K. Nakamura, Y. Yoshimoto, Y. Nohara, and M. Imada, arXiv:1007.4429. [Preview Abstract] |
Thursday, March 24, 2011 11:51AM - 12:03PM |
W18.00004: Beyond Landau Adiabacity: Weak Interaction Quenches in a Fermi Gas Stefan Kehrein, Michael Moeckel The crossover from Landau's Fermi-liquid paradigm with adiabatic switching on of the interaction to a sudden interaction quench is investigated [Phys. Rev. Lett. 100, 175702 (2008); Ann. Phys. 324, 2146 (2009); New J. Phys. 12, 055016 (2010)]. The real time dynamics for weak interactions is calculated in a systematic expansion and one finds three clearly separated time regimes: (i) An initial buildup of correlations where the quasiparticles are formed. (ii) An intermediate quasi-steady prethermalized regime resembling a zero temperature Fermi liquid with a nonequilibrium quasiparticle distribution function. (iii) The long-time limit described by a quantum Boltzmann equation leading to thermalization of the momentum distribution function. This thermalization behavior is contrasted with interaction quenches in 1d models. [Preview Abstract] |
Thursday, March 24, 2011 12:03PM - 12:15PM |
W18.00005: Dynamical Freezing of Response in Driven Many-Body Quantum System Arnab Das We show, that the response of a periodically driven quantum many- body system may freeze drastically, when driven with certain combinations of driving parameters (amplitude and frequency). We demonstrate this effect with analytical results for a broad class of integrable quantum spin models (illustrated particularly for one-dimensional Transverse Ising Model)and direct numerical integration data for large system-size. We show that the immunity of the freezing behavior to external noise can be controlled arbitrarily by controlling the strength of the local (on-site) field. [Preview Abstract] |
Thursday, March 24, 2011 12:15PM - 12:27PM |
W18.00006: Bethe-Salpeter Equation calculations of transition metal L$_{2,3}$ edge x-ray spectra including multiplet effects J. Vinson, E.L. Shirley, J.J. Rehr Calculations of x-ray spectra at transition metal L$_{2,3}$ edges often present theoretical difficulties due to strong core-hole multiplet effects. Here we discuss an {\it ab initio} method for treating these effects following the Bethe-Salpeter Equation (BSE) approach of Shirley.\footnote{E. L. Shirley, J. Electron Spectrosc. Relat. Phenom. {\bf 144}, 1187 (2005).} The method builds in spin-orbit interactions, intra-atomic Coulomb integrals, core-hole screening, and band-structure effects, and thus accounts for multiplet effects without the need for phenomenological ligand-field parameters. The method has been implemented in the core-level BSE code OCEAN,\footnote{J. Vinson, E. L. Shirley, J. J. Rehr, and J. J. Kas, arXiv:1010.0025} which uses as input wavefunctions from planewave, pseudopotential DFT calculations and PAW transition matrix elements. Examples are presented for several transition metal systems and compared with experiment. [Preview Abstract] |
Thursday, March 24, 2011 12:27PM - 12:39PM |
W18.00007: ABSTRACT WITHDRAWN |
Thursday, March 24, 2011 12:39PM - 12:51PM |
W18.00008: Real Space Green's Function Calculations of RIXS J.J. Kas, J.J. Rehr, J.A. Soininen We present an {\it ab initio} theory of resonant inelastic x-ray scattering (RIXS) based on the real-space multiple scattering Green's function (RSGF) formalism and a quasi-boson model Hamiltonian. It is shown that the RIXS spectrum is quasi-local in nature, depending primarily on the Green's function close to the absorbing site. Based on several assumptions, we derive an approximation to the RIXS spectrum in terms of a convolution of the x-ray absorption and x-ray emission spectra. In addition, quasi-particle self-energy and other many-body effects are calculated using a many-pole model dielectric function, and included via a convolution of the RIXS spectrum with an energy dependent spectral function. Core hole effects are also investigated. The method is implemented in an extension of the RSMS code FEFF90\footnote{J.J. Rehr et al., Comptes Rendus Phys. \textbf{10}, 548 (2009)} and illustrated with several examples. Results are found to be in qualitative agreement with experiment. [Preview Abstract] |
Thursday, March 24, 2011 12:51PM - 1:03PM |
W18.00009: Finite-Temperature Constraint-Pairing Mean Field Theory Jianmin Tao, Gustavo Scuseria Recently Tsuchimochi and Scuseria have developed a constrained-pairing mean-field theory (CPMFT), based on the Hartree-Fock-Bogoliubov theory. Application to molecular systems shows that CPMFT can accurately describe the binding energy curve in the dissociation of molecules, where electron correlation is strong. However, because CPMFT is a zero-temperature theory, it is not suitable for the description of high-temperature superconductivity and normal state of high-temperature superconductors. Here a finite-temperature generalization is formulated for the thermodynamic state of quantum many-body systems. [Preview Abstract] |
Thursday, March 24, 2011 1:03PM - 1:15PM |
W18.00010: Fermionic duality approach to strongly-interacting lattice models Joe Mitchell, Tigran Sedrakyan, Victor Galitski We derive an exact Grassmann path-integral representation for strongly interacting fermion systems that is dual to the conventional Hubbard-Stratonovich approach. In contrast to the latter, we decouple the interaction Hamiltonian by introducing additional (dual) fermionic fields. This fermionic decoupling naturally forms in particle-hole channels and leads to alternative order parameters given in terms of the dual fields. The new formalism is tested by calculating the partition function in a simple solvable model with four-fermion interaction and is argued to be very effective for strong or repulsive interactions. [Preview Abstract] |
Thursday, March 24, 2011 1:15PM - 1:27PM |
W18.00011: ABSTRACT WITHDRAWN |
Thursday, March 24, 2011 1:27PM - 1:39PM |
W18.00012: Breakdown of the coherent state path integral: two simple examples Justin Wilson, Victor Galitski We show how the time-continuous coherent state path integral breaks down for both the single-site Bose-Hubbard model and the spin path integral. Specifically, when the Hamiltonian is quadratic in a generator of the algebra used to construct coherent states, the path integral fails to produce correct results following from an operator approach. As suggested by previous authors, we note that the problems do not arise in the time-discretized version of the path integral. Further, a na\"ive use of the semiclassics agrees with our conclusions. [Preview Abstract] |
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