Bulletin of the American Physical Society
43rd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 57, Number 5
Monday–Friday, June 4–8, 2012; Orange County, California
Session G1: Invited Session: Disorder in Cold Atoms Systems |
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Chair: Steven Rolston, University of Maryland Room: Grand Ballroom BCD |
Wednesday, June 6, 2012 8:00AM - 8:30AM |
G1.00001: Glassy Behavior in a Binary Atomic Mixture Invited Speaker: Dominik Schneble Atomic mixtures in component-specific optical lattices allow for the study of a broad range of interaction-induced phenomena. In a recent experiment [1], we have studied the effects of randomly localized impurity atoms on transport behavior of lattice-modulated 1D Bose gases, and compared them to quasidisorder from an incommensurate lattice. Whereas deeply in the strongly interacting regime the two realizations of disorder have comparable effects, both producing signatures of Bose-glass formation, we found dramatic difference near the superfluid-to-insulator transition. In this transition region, the random, uncorrelated disorder of the impurities leads to a shift of the critical lattice depth for the breakdown of transport in the 1D Bose gas, while no such shift is seen for the correlated quasidisorder of the incommensurate optical lattice. Our findings, which are consistent with recent predictions for interacting bosons in one dimension, illustrate the important role of correlations in disordered atomic systems. \\[4pt] [1] B. Gadway et al, PRL \textbf{107}, 145306 (2011) [Preview Abstract] |
Wednesday, June 6, 2012 8:30AM - 9:00AM |
G1.00002: Three-Dimensional Anderson Localization of Ultracold Matter Invited Speaker: Brian DeMarco Anderson localization (AL) is a ubiquitous interference phenomenon in which waves fail to propagate in a disordered medium. We observe three-dimensional AL of noninteracting ultracold matter by allowing a spin-polarized atomic Fermi gas to expand into a disordered potential. A two-component density distribution emerges consisting of an expanding mobile component and a nondiffusing localized component. We extract a mobility edge that increases with the disorder strength, whereas the thermally averaged localization length is shown to decrease with disorder strength and increase with particle energy. Progress toward combining disordered fermions with an optical lattice in order to realize the disordered (Fermi-)Hubbard model will be discussed. [Preview Abstract] |
Wednesday, June 6, 2012 9:00AM - 9:30AM |
G1.00003: Coexistence of Localized and Extended States in a Disordered Trap Invited Speaker: Laurent Sanchez-Palencia We study Anderson localization of matterwaves in a disordered potential combined with an inhomogeneous trap. We show that the spectrum displays both localized and extended states, which coexist at intermediate energies. The coexistence of localized and extended states is in apparent contradiction with the Mott argument, which is widely accepted and verified for several models of homogeneous disorder. We argue and prove numerically that the argument fails when an inhomogeneous trap is superimposed with the disorder. In the coexistence region, we find that the extended states result from confinement by the trap and are weakly affected by the disorder. Conversely, the localized states correspond to eigenstates of the disordered potential, which are only affected by the trap via an inhomogeneous energy shift. In addition to other inhomogeneous systems, these results are directly relevant to disordered quantum gases, which are confined in traps and we propose a realistic scheme to observe the coexistence of localized and extended states in these systems. \\[4pt] [1] L.~Pezz\'e and L.~Sanchez-Palencia, Phys. Rev. Lett. \textbf{106}, 040601 (2011). [Preview Abstract] |
Wednesday, June 6, 2012 9:30AM - 10:00AM |
G1.00004: Simulating quantum transport with atoms and light Invited Speaker: Vincent Josse The transport of quantum particles in non ideal material media (eg the conduction of electrons in an imperfect crystal) is strongly affected by scattering from impurities of the medium. Even for a weak disorder, semi-classical theories, such as those based on the Boltzmann equation for matter-waves scattering from the impurities, often fail to describe transport properties and full quantum approaches are necessary. The properties of the quantum systems are of fundamental interest as they show intriguing and non-intuitive phenomena that are not yet fully understood such as Anderson localization, percolation, disorder-driven quantum phase transitions and the corresponding Bose-glass or spin-glass phases. Understanding quantum transport in amorphous solids is one of the main issues in this context, related to electric and thermal conductivities. Ultracold atomic gases can now be considered to revisit the problem of quantum conductivity and quantum transport under unique control possibilities. Dilute atomic Bose-Einstein condensates (BEC) and degenerate Fermi gases (DFG) are produced routinely taking advantage of the recent progress in cooling and trapping of neutral atoms. Transport has been widely investigated in controlled potentials with no defects, for instance periodic potentials (optical lattices). Controlled disordered potentials can also be produced with various techniques such as the use of magnetic traps designed on atomic chips with rough wires, the use of localized impurity atoms, the use of radio-frequency fields or the use of optical potentials. This recently lead to the observation of the Anderson Localization of a BEC in 1D and 3D, and the study of diffusion properties during matter-wave transport. [Preview Abstract] |
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