Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session K13: Application of Monte Carlo Techniques to Cold Atom SystemsInvited
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Sponsoring Units: DAMOP DCOMP Chair: Barry Schneider, NIST/NSF Room: 309 |
Wednesday, March 16, 2016 8:00AM - 8:36AM |
K13.00001: Coexistence, Interfacial Energy and the Fate of Microemulsions of 2D Dipolar Bosons Invited Speaker: Massimo Boninsegni The superfluid-crystal quantum phase transition of a system of purely repulsive dipolar bosons in two dimensions has been the subject of a lot of theoretical study, mainly because of some intriguing predictions by Spivak and Kivelson (2004) regarding an exotic, intermediate "microemulsion" that should appear at low temperature between the crystal and the superfluid. We investigated this scenario by means of Quantum Monte Carlo simulations at zero temperature, determined freezing and melting densities, and estimated the energy per unit length of a macroscopic interface separating the coexisting crystal and superfluid phases. The results rule out quantitatively the microemulsion scenario for any physical realization of this system, given the exceedingly large predicted size of the bubbles. Reference: S. Moroni and M. Boninsegni, Phys. Rev. Lett. {\bf 113}, 240407 (2014) [Preview Abstract] |
Wednesday, March 16, 2016 8:36AM - 9:12AM |
K13.00002: Quantum spin dynamics and entanglement in systems with long-range interactions Invited Speaker: Ana M Rey One of the fundamental goals of modern quantum sciences is to learn how to control and manipulate non-equilibrium many-body systems and use them to make powerful and improved quantum devices, materials and technologies. However, out-of-equilibrium systems are complex, typically strongly correlated and entangled, and thus to model them we are in an urgent need of new methodologies. In this talk I will discuss new theoretical methods that we have developed to investigate emergent non-equilibrium phenomena in driven-dissipative spin systems interacting via long-range interactions. I will show we can capture the dynamics of correlations and entanglement in close systems and the interplay between dissipation and entanglement in open quantum systems including spin-boson models. As a specific application I will discuss the use of our methods to model the spin dynamics exhibited by arrays of trapped ions with controllable long-range interactions. I will show that our predictions are consistent with recent experimental measurements. I will also discuss new protocols to diagnostic and characterize entanglement based on well-established NMR protocols [Preview Abstract] |
Wednesday, March 16, 2016 9:12AM - 9:48AM |
K13.00003: Universal scaling of density and momentum distributions in Lieb-Liniger gases Invited Speaker: Marcos Rigol We present numerically exact results for the scaling of density and momentum distribution functions of harmonically trapped one-dimensional bosons with repulsive contact interactions. We consider systems in the continuum [1], and in the presence of a lattice [2,3], both in the ground state [1,2] and at finite temperature [1,3]. We use path integral quantum Monte Carlo with worm updates in calculations at finite interaction strengths, and the Bose-Fermi mapping in the Tonks-Girardeau limit. We first discuss the homogeneous case and, within the local density approximation, use it to motivate the scaling in the presence of a harmonic trap. For the momentum distribution function, we pay special attention to the high momentum tails and their $k^{-4}$ asymptotic behavior. When available, we compare our results to experimental measurements of the momentum distribution function of ultracold bosonic gases in two-dimensional optical lattices.\\ References:\\ {[1]} W. Xu and M. Rigol. Universal scaling of density and momentum distributions in Lieb-Liniger gases. arXiv:1508.07011.\\ {[2]} M. Rigol and A. Muramatsu. Universal properties of hard-core bosons confined on one-dimensional lattices. Phys. Rev. A {\bf 70}, 031603(R) (2004).\\ {[3]} M. Rigol. Finite-temperature properties of hard-core bosons confined on one-dimensional optical lattices. Phys. Rev. A {\bf 72}, 063607 (2005). [Preview Abstract] |
Wednesday, March 16, 2016 9:48AM - 10:24AM |
K13.00004: Cooling Atomic Gases With Disorder Invited Speaker: Richard Scalettar Cold atomic gases have proven capable of emulating a number of fundamental condensed matter phenomena including Bose-Einstein condensation, the Mott transition, Fulde-Ferrell-Larkin-Ovchinnikov pairing and the quantum Hall effect. Cooling to a low enough temperature to explore magnetism and exotic superconductivity in lattices of fermionic atoms remains a challenge. We propose a method to produce a low temperature gas by preparing it in a disordered potential and following a constant entropy trajectory to deliver the gas into a non-disordered state which exhibits these incompletely understood phases. We show, using quantum Monte Carlo simulations, that we can approach the Ne\'el temperature of the three-dimensional Hubbard model for experimentally achievable parameters. Recent experimental estimates suggest the randomness required lies in a regime where atom transport and equilibration are still robust. Thereza Paiva, Ehsan Khatami, Shuxiang Yang, Valery Rousseau, Mark Jarrell, Juana Moreno, Randall G. Hulet, and Richard T. Scalettar, arXiv:1508.02613 [Preview Abstract] |
Wednesday, March 16, 2016 10:24AM - 11:00AM |
K13.00005: Diagrammatic Monte Carlo study of mass-imbalanced Fermi-polaron system Invited Speaker: Lode Pollet After a brief introduction and review of diagrammatic Monte Carlo, I present our results for the three-dimensional Fermi-polaron system with mass-imbalance, where an impurity interacts resonantly with a noninteracting Fermi sea whose atoms have a different mass. This method allows to go beyond frequently used variational techniques by stochastically summing all relevant impurity Feynman diagrams up to a maximum expansion order limited by the sign problem. The polaron energy and quasiparticle residue can be accurately determined over a broad range of impurity masses. Furthermore, the spectral function of an imbalanced polaron demonstrates the stability of the quasiparticle and allows to locate in addition also the repulsive polaron as an excited state. The quantitative exactness of two-particle-hole wave-functions is investigated, resulting in a relative lowering of polaronic energies in the mass-imbalance phase diagram. Tan’s contact coefficient for the mass-balanced polaron system is found in good agreement with variational methods. Mass-imbalanced systems can be studied experimentally by ultracold atom mixtures like $^6$Li-$^{40}$K. I will discuss some open questions and links with recent experiments. [Preview Abstract] |
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