Bulletin of the American Physical Society
APS March Meeting 2011
Volume 56, Number 1
Monday–Friday, March 21–25, 2011; Dallas, Texas
Session D45: Many Body Physics of Quantum Gases in Reduced Dimension |
Hide Abstracts |
Sponsoring Units: DAMOP Chair: Ana Maria Rey, JILA/University of Colorado Room: A310 |
Monday, March 21, 2011 2:30PM - 2:42PM |
D45.00001: Moving Impurities and Spin-Boson Systems in One-Dimensional BECs Thomas Schmidt, Peter Orth, Karyn Le Hur We theoretically investigate the dynamics of two moving impurities immersed in a one-dimensional interacting Bose liquid. Interactions between the two impurities are mediated via excitations in the quantum liquid, and lead to correlations between them. For certain parameter regimes, the system can be mapped onto a spin-boson model, in which the relative momentum of the impurities plays the role of a spin-1/2 or spin-1. We will discuss the implications of the spin-impurity model onto observables of the liquid and impurities. [Preview Abstract] |
Monday, March 21, 2011 2:42PM - 2:54PM |
D45.00002: Exact result for the three-body local correlator in the 1D Bose gas at finite temperature Marton Kormos, Adilet Imambekov The 1D Bose gas with Dirac-delta interaction (Lieb--Liniger model) gives a very good description of cold atomic gases confined in quasi one-dimensional waveguides. While the model is integrable by means of the Bethe Ansatz it can also be regarded as a particular non-relativistic limit of an integrable relativistic quantum field theory, the sinh-Gordon model. This fact can be exploited to calculate form factors and correlation functions for the Bose gas. We derive an exact expression for the finite temperature expectation value of the third power of the density operator $:\rho^3:$, a quantity which is closely related to the three-body losses in cold atom experiments. We achieve this by summing up an infinite integral series obtained using the connection with the sinh-Gordon model. Our method can be generalized to other local correlators. [Preview Abstract] |
Monday, March 21, 2011 2:54PM - 3:06PM |
D45.00003: The density profile of interacting Fermions in a one-dimensional optical trap Sebastian Eggert, Stefan Soeffing The density distribution of the Hubbard model in a one-dimensional external harmonic potential is investigated in order to study the effect of the confining trap. The broadening of the Fermion cloud with increasing interaction is analyzed in detailed, which can be described by a surprisingly simple scaling form. Strong superimposed ``Friedel'' oscillations are always present despite the absence of any hard wall boundaries. The wavelength of the dominant oscillation changes with interaction, which indicates the crossover to a spin-incoherent regime. We present an analytical formula, which describes the behavior of the oscillations very well for all interactions strengths and in return gives some insight for the use of bosonization in a trapping potential. [Preview Abstract] |
Monday, March 21, 2011 3:06PM - 3:18PM |
D45.00004: Pairing correlations in one-dimensional Bose-Fermi mixtures with molecular boundstates Shimul Akhanjee, Masahisa Tsuchiizu, Akira Furusaki We study the ground-state properties of one-dimensional (1D) 3-component mixtures of Tonks bosons having infinite repulsion and nearly free fermionic atoms that can combine to form molecular fermions. Using a bosonization scheme, the form of the interaction is equivalent to the hopping term between weakly coupled spinless Tomonaga Luttinger liquids (TLL). Upon reduction of the energy scale, the 3-component TLL system scales down into a phase with coupled massive modes accompanied by pairing correlations. [Preview Abstract] |
Monday, March 21, 2011 3:18PM - 3:30PM |
D45.00005: Scaling of noise correlations in one-dimensional lattice hard-core boson systems Kai He, Marcos Rigol Noise correlations are studied for systems of hard-core bosons in one-dimensional lattices. We use an exact numerical approach based on the Bose-Fermi mapping and properties of Slater determinants. We focus on the scaling of the noise correlations with system size in superfluid and insulating phases, which are generated in the homogeneous lattice, with period-two superlattices, and with uniformly distributed random diagonal disorder. For the superfluid phases, the leading contribution is shown to exhibit a density independent scaling proportional to the system size, while the first subleading term exhibits a density dependent power-law exponent. [Preview Abstract] |
Monday, March 21, 2011 3:30PM - 3:42PM |
D45.00006: Double occupancy as a probe of the Mott transition for fermions in one-dimensional optical lattices Jorge Quintanilla, Vivaldo L. Campo, Jr, Vito Scarola, Chris Hooley, Klaus Capelle We study theoretically double occupancy D as a probe of the Mott transition for trapped fermions in one-dimensional optical lattices and compare our results to the three-dimensional case. The ground state is described using the Bethe Ansatz in a local density approximation and the behavior at finite temperatures is modelled using a high-temperature series expansion. In addition, we solve analytically the model in the limit in which the interaction energy is the dominant energy scale. We find that enhanced quantum fluctuations in one dimension lead to increased double occupancy in the ground state, even deep in the Mott insulator region of the phase diagram. Similarly, thermal fluctuations lead to high double occupancies at high temperatures. Nevertheless, D is found to be a good indicator of the Mott transition just as in three dimensions. We discuss possible experiments to verify these results and argue that the one-dimensional Hubbard model could be used as a benchmark for quantitative quantum analogue simulations. [Preview Abstract] |
Monday, March 21, 2011 3:42PM - 3:54PM |
D45.00007: ABSTRACT WITHDRAWN |
Monday, March 21, 2011 3:54PM - 4:06PM |
D45.00008: Analysis of the single-particle excitation spectrum of ultracold fermions in 1D optical lattices Atsushi Yamamoto, Susumu Yamada, Masahiko Machida We present single-particle excitation spectra of ultracold fermions in one-dimensional(1D) optical lattices by using dynamical density-matrix renormalization group (DDMRG) method. Our model is described by a Hubbard model with the harmonic trap potential. We find that the spectra show many kinds of intriguing structures owing to the harmonic trap potential and on-site interaction. In an analysis of weakly-interaction regimes, we find that the spectrum structure changes from a typical Hubbard band as obtained from periodical 1D lattice to band branching as increasing the trap potential, and finally, we observe clear discrete bound-state levels. On the other hand, in case of strongly-interacting regimes, we confirm the multiple flat bound-state levels lying above 1D Tomonaga-Luttinger (TL) liquid spectrum on a central Mott-plateau phase surrounded by metallic regions. Furthermore, we also investigate spectral changes as a metallic state partially emerges at the center region and find one-dimensional TL spectrum breakdown with an emergence of a new dispersive band due to the central metal portion. The observed features are closely related with the spectral changes when doping into Mott insulator. We will show the more details of spectra in 1D fermionic optical lattices by comparing non-trapped uniform 1D spectra. [Preview Abstract] |
Monday, March 21, 2011 4:06PM - 4:18PM |
D45.00009: A quantum Monte Carlo study of the two-component mixture of hard-core bosons in one dimension Min-Chul Cha, Jong-Geun Shin, Inho Jeon The two-component mixture of hard-core bosons in one dimension is studied by quantum Monte Carlo simulations. A rich variety of phases exists in the parameter space of the inter-species interaction strengths, the ratio of the hopping amplitudes between two species, and the filling fractions. Physical properties of different phases are investigated by measuring the superfluid stiffness, the counter-flow stiffness, the compressibility, and the structure factor. We examine the nature of some phase transitions between a superfluid and an insulator and the 1st-order transition in the occurrence of phase separations. [Preview Abstract] |
Monday, March 21, 2011 4:18PM - 4:30PM |
D45.00010: Fermionic Cold Atom Systems in Mixed Dimensions Kyle Irwin, Shan-Wen Tsai Cold atom experiments can now realize mixtures of components that move in different dimensions [1]. We investigate such a system with two species of fermions. One species, f-fermions, moves on a two-dimensional square lattice. Another species, c-fermions, is constrained to move on a one-dimensional lattice embedded in the square lattice of f-fermions. We investigate the effective one-dimensional system who's interactions are mediated by the two-dimensional system, and explore effective theories, quantum phases, correlations, and relevant energy scales for various fillings of the mixed dimensional system using a functional renormalization group approach. \\[4pt] [1] G. Lamporesi, J. Catani, G. Barontini, Y. Nishida, M. Inguscio, and F. Minardi, Phys. Rev. Lett. 104, 153202 (2010) [Preview Abstract] |
Monday, March 21, 2011 4:30PM - 4:42PM |
D45.00011: Long range bosonic correlations in 2D optical lattice traps K.W. Mahmud, E.N. Duchon, Y. Kato, N. Kawashima, R.T. Scalettar, N. Trivedi We use quantum Monte Carlo (QMC) simulations to study the combined effects of harmonic confinement and temperature for bosons in a two dimensional optical lattice. We present the scale invariant, finite temperature, state diagram for the Bose- Hubbard model in terms of experimental parameters - the particle number, confining potential and interaction strength. We examine the correlation decay of the superfluid trapped in annular rings, and find that the width of the superfluid ring determines a distance after which the correlation decays faster than in an equivalent 2D superfluid. At zero temperature, the correlation decay is intermediate between 1D and 2D decay, while at finite temperature, the decay is similar to a 1D decay at a much lower temperature. These provide the strongest evidence for the breakdown of the local density approximation (LDA) in trapped superfluid bosons. [Preview Abstract] |
Monday, March 21, 2011 4:42PM - 4:54PM |
D45.00012: Interference signatures of thermal and quantum phase fluctuations in the two dimensional Bose-Hubbard Model Mason Swanson, Yen Lee Loh, Nandini Trivedi Superfluidity in the Bose-Hubbard model is destroyed by the interplay of thermal and quantum phase fluctuations. In two dimensions, Berezinskii-Kosterlitz-Thouless theory predicts that deep in the superfluid phase quasi-long-range order is destroyed by the proliferation of thermally induced free vortices. As the Mott insulator regime is approached, the effect of quantum phase fluctuations must also be taken into account. By using a (2 + 1)-dimensional XY phase model, we investigate the signatures of thermal and quantum vortices in interference patterns. The possibility of extracting spatial and temporal correlation lengths from such interference images provides a new experimental probe for characterizing the state of ultracold atomic gases in 2D optical lattices. [Preview Abstract] |
Monday, March 21, 2011 4:54PM - 5:06PM |
D45.00013: The Fluctuation-Dissipation Theorem at Low Temperatures in a 2D Optical Lattice Eric Duchon, Yasuyuki Kato, Naoki Kawashima, Nandini Trivedi We calculate local density fluctuations and the local compressibility\footnote{Q. Zhou, et al., {\em Phys. Rev. Lett.} {\bf 103}, 085701 (2009).} of bosons in a two dimensional optical lattice as a function of temperature $T$ and the tuning parameter $U/t$, the on-site boson repulsion strength in units of hopping, using worldline Quantum Monte Carlo. Our numerical results, coupled with the quantum fluctuation-dissipation theorem applied locally, make significantly different predictions for direct simulations of lattice bosons in a harmonic trap versus simulations that treat the trap within a local density approximation, especially at low temperatures. We discuss implications of our results for local thermometry, equilibration and characterization of the quantum critical regime. [Preview Abstract] |
Monday, March 21, 2011 5:06PM - 5:18PM |
D45.00014: The Effects of Disorder on a Quasi-2D System of Ultracold Atoms Matthew Beeler, Matthew Reed, Tao Hong, Steven Rolston An ultra-cold gas of atoms can be used to create many different model Hamiltonians. When tightly confined in one spatial dimension, the gas can become effectively two-dimensional. At low temperature, a quasi-2D Bose gas undergoes a Berezinskii-Kosterlitz-Thouless phase transition to a superfluid, mediated by the binding and unbinding of vortex pairs. As disorder affects vortex transport properties, a slight amount of fine-grain disorder in the potential energy may alter the properties of this phase transition. We will present experimental observations of a 2D Bose gas of rubidium atoms in the presence of disorder created by a laser speckle field. [Preview Abstract] |
Monday, March 21, 2011 5:18PM - 5:30PM |
D45.00015: Atomic Fermi superfluids in a honeycomb optical lattice: Supercurrents and dynamical instabilities Shunji Tsuchiya, Ramachandran Ganesh, Arun Paramekanti Cold Fermi and Bose atoms on a honeycomb lattice have been of great recent interest given the possibility to simulate graphene physics and to realize interesting topological phases of matter.\footnote{A. H. Castro Neto et al., Rev. Mod. Phys. 81, 109 (2009).}$^,$\footnote{C. L. Kane and E. J. Mele, Phys. Rev. Lett, 95, 226801 (2005).}$^,$\footnote{A. Kitaev, Ann. Phys. (N.Y.) 321, 2 (2006).} We study the attractive Hubbard model of fermions on the honeycomb lattice in order to explore the strongly correlated superfluid state in this lattice geometry. We calculate the superfluid order parameter and collective modes in the presence of a superfluid flow in order to investigate the superflow stability. We find that the superfluid order parameter and density fluctuations exhibit nontrivial dependence on the flow, and these collective modes lead to novel dynamical instabilities. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700