Bulletin of the American Physical Society
2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009; Pittsburgh, Pennsylvania
Session J16: Focus Session: Disorder in Ultra-Cold Gases |
Hide Abstracts |
Sponsoring Units: DAMOP Chair: Maxim Olshanyi, University of Massachusetts, Boston Room: 317 |
Tuesday, March 17, 2009 11:15AM - 11:27AM |
J16.00001: The Role of Interactions in Disorder Induced Damping of Dipole Oscillations of a Bose-Einstein Condensate Scott Pollack, D. Dries, T.A. Corcovilos, R.G. Hulet We investigate the damping of dipole oscillations of a $^7$Li Bose-Einstein condensate (BEC) in a disordered optical potential. In our highly tunable system we vary the disorder strength $V_D$, the initial velocity of the BEC, and the chemical potential $\mu$ by adjusting the $s$-wave scattering length $a$ via a Feshbach resonance. We observe the breaking of superfluid flow, for values of $V_D$ as small as $0.1\,\mu$, and cessation of motion for $V_D \sim \mu$. Counter-intuitively, at supersonic velocities the flow becomes asymptotically dissipationless regardless of the disorder strength. We test the validity of the scaling $V_D/\mu$ over several decades of $a$, including values of $a$ as small as $0.01\,a_0$, where magnetic dipole effects dominate. We also report on observations of dissipative flow of nearly non-interacting ideal quantum gases and bright matter-wave solitons. [Preview Abstract] |
Tuesday, March 17, 2009 11:27AM - 11:39AM |
J16.00002: Disorder effects in the evolution from BCS to BEC superfluidity Li Han, Carlos A. R. Sa de Melo We discuss the effects of disorder on the critical temperature of superfluids during the evolution from BCS to BEC. For s-wave superfluids we find that the critical temperature is weakly affected by disorder in the BCS regime as described in Anderson’s theorem, even less affected by disorder at zero chemical potential (near unitarity), but strongly affected by disorder in the BEC regime, where Anderson's theorem does not apply. This suggests that the superfluid is more robust to the effects of disorder at the interaction parameter where the chemical potential vanishes (close to unitarity). We construct a three dimensional phase diagram of critical temperature, disorder and interaction parameter [1], and show that there are regions of localized superfluidity, as well as insulating regions due to Anderson localization of fermions (BCS regime) and molecular bosons (BEC regime). The phase diagram for higher angular momentum (e.g. p-wave and d-wave) is also analyzed, where the effects of disorder are much more dramatic in the BCS regime in comparison to the s-wave case because pair breaking is strong, while the disorder effects in BEC regime are similar to what occurs in the s-wave case. \newline [1] Li Han, C. A. R. Sa de Melo, arXiv:0812.xxxx [Preview Abstract] |
Tuesday, March 17, 2009 11:39AM - 11:51AM |
J16.00003: Magnetizm Localization and Hole Localization in Fermionic Atoms Loaded on Optical Lattice Masahiko Okumura, Susumu Yamada, Nobuhiko Taniguchi, Masahiko Machida In order to study an interplay of disorder, correlation, and spin imbalance on antiferromagnetism, we systematically explore the ground state of one-dimensional spin-imbalanced Fermionic atoms loaded on an optical lattice by using the density-matrix renormalization group method [1]. We find that disorders localize the antiferromagnetic spin density wave induced by imbalanced fermions and the increase of the disorder magnitude shrinks the areas of the localized antiferromagnetized regions. Moreover, the antiferromagnetism finally disappears above a large disorder. We also study hole doped cases [2]. Concentrating on the doped-hole density profile, we find in a large $U/t $regime that the clean system exhibits a simple fluid-like behavior whereas finite disorders create locally Mott regions which expand their area with increasing the disorder strength contrary to the conventional sense. References [1] M. Okumura, S. Yamada, N. Taniguchi, and M. Machida, arXiv:0810:3953. [2] M. Okumura, S. Yamada, N. Taniguchi, and M. Machida, Phys. Rev. Lett. \textbf{101} 016407 (2008). [Preview Abstract] |
Tuesday, March 17, 2009 11:51AM - 12:03PM |
J16.00004: ABSTRACT WITHDRAWN |
Tuesday, March 17, 2009 12:03PM - 12:15PM |
J16.00005: Dynamical Effects of Disorder in Optical Lattices M. Beeler, E.E. Edwards, Tao Hong, S.L. Rolston The precise control available in systems of neutral atoms confined in optical lattices makes them an ideal place to investigate the effects of disorder on crystal structure. We experimentally investigate how disorder affects the dynamical properties of these systems. Using a 1D optical lattice with the addition of one or two weak incommensurate lattices, we investigate the adiabaticity criteria for loading the ground state of the disordered lattice. We find that even a very small amount of disorder greatly increases the timescale needed for adiabatic loading. We attribute this change to the large change in the ground state of the wavefunction with the addition of disorder, as the wavefunction becomes localized. In addition, we will report on experimental efforts to study the effects of disorder in two-dimensional systems and on the timescales of thermalization in one dimension. [Preview Abstract] |
Tuesday, March 17, 2009 12:15PM - 12:27PM |
J16.00006: Impurity crystal in a Bose-Einstein condensate David Roberts, Sergio Rica We investigate the behavior of impurity fields immersed in a larger condensate field. The conditions for stability and collapse of this system will be presented. We discuss the localization of a single impurity field within a condensate and note the effects of surface energy. We derive the functional form of the attractive interaction between two impurities due to mediation from the condensate in 1, 2, and 3 dimensions. Generalizing the analysis to $N$ impurity fields, we show that within various parameter regimes a crystal of impurity fields can form spontaneously in the condensate. Finally, we show the system of condensate and crystallized impurity structure to have nonclassical rotational inertia, which is characteristic of superfluidity, i.e. the system can be seen to exhibit supersolid behavior. [Preview Abstract] |
Tuesday, March 17, 2009 12:27PM - 1:03PM |
J16.00007: Experiments on Disordered Quantum Gases Invited Speaker: |
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