Bulletin of the American Physical Society
47th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 61, Number 8
Monday–Friday, May 23–27, 2016; Providence, Rhode Island
Session C3: Invited Session: Localization in Disordered PotentialsInvited Press
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Chair: Ken O'Hara, Pennsylvania State University Room: Ballroom D |
Tuesday, May 24, 2016 2:00PM - 2:30PM |
C3.00001: Holographic Scaling and Dynamical Gauge Effects in Disordered Atomic Gases Invited Speaker: Nathan Gemelke Quantum systems with strong disorder, and those far from equilibrium or interacting with a thermal reservior, present unique challenges in a range of physical contexts, from non-relativistic condensed-matter settings, such as in study of localization phenomena, to relativistic cosmology and the study of fundamental interactions. Recently, two related concepts, that of the entropy of entanglement, and the controversial suggestion of entropic emergent gravity, have shed insight on several long-standing questions along these lines, suggesting that strongly disordered systems with causal barriers (either relativistic or those with Lieb-Robinson-like bounds) can be understood using holographic principles in combination with the equivalence between quantum vacuua thermal baths via the Unruh effect. I will discuss a range of experiments performed within a strong, topologically disordered medium for neutral atoms which simultaneously introduces quenched disorder for spin and mass transport, and provides simple mechanisms for open coupling to various types of dissipative baths. Under conditions in which a subset of quantum states are continuously decoupled from the thermal bath, dark state effects lead to slow light phenomena mimicking gravitational lensing in general relativity in a characterizable table-top disordered medium. Non-equilibrium steady-states are observed in direct analogy with the evaporation of gravitational singularities, and we observe scaling behaviors that can be directly connected to holographic measures of the information contained in disorder. Finally, I will show how a dynamic-gauge-field picture of this and similar systems can lead to a natural description of non-equilibrium and disordered phenomena, and how it provides some advantages over the Harris and Luck criteria for describing critical phenomena. Connections between out-of-equilibrium dynamics and some long-unresolved issues concerning the existence of a gauge-boson mass gap in certain Yang-Mills models will also be discussed, as will dynamic gauge effects in experimental many-body systems. [Preview Abstract] |
Tuesday, May 24, 2016 2:30PM - 3:00PM |
C3.00002: Anderson localization of matter waves in 3D anisotropic disordered potentials Invited Speaker: Marie Piraud We study quantum transport and Anderson localization of matterwaves in 3 dimensional correlated disorder, focusing on the effects of the anisotropy. Indeed, understanding the anisotropy effects is fundamental for experiments with ultracold atoms as well as for several other systems, such as electrons in MOSFETs, light in biological medium, liquid crystals. A major challenge is to understand whether the anisotropy of the diffusion tensor is altered by the interference terms at the origin of Anderson localization. In particular, its anisotropy at the mobility edge remains to be investigated. So far, all theoretical analysis have assumed - more or less implicitly - that the anisotropy of the diffusion tensor is preserved by interference effects [1], and have focussed on the vanishing of diffusion as a whole. \medskip In this talk, I will start by presenting the usual description of matterwave transport in disordered medium. I will then present our method to go beyond the standard self-consistent theory, which includes in particular the full anisotropic structure of the spectral function. It thus avoids the infrared divergence [2] of the usual self-consistent theory and, most importantly, does not make any assumption on the anisotropy of the renormalized diffusion tensor when including quantum interference terms. Using a generic model of disorder with elongated correlations, we find that the diffusion tensor is strongly affected by the quantum interference terms and that the anisotropy strongly diminishes in the vicinity of the mobility edge [3]. \medskip Our work paves the way to further investigation with speckle potentials, which are directly relevant to ultracold-atom experiments. It will permit comparison with previous predictions for the mobility edge [4,5] and shed new light on ongoing experiments in the field of ultracold atoms. \medskip \\ {[1]} P. W\"olfle and R. N. Bhatt, Phys. Rev. B {\bf 30}, 3542 (1984)\\ {[2]} A. Yedjour and B. A. van Tiggelen, Eur. Phys. J. D {\bf 59}, 249 (2010)\\ {[3]} M. Piraud, L. Sanchez-Palencia, and B. van Tiggelen, Phys. Rev. A {\bf 90}, 063639 (2014)\\ {[4]} M. Piraud, L. Pezz\'e, and L. Sanchez-Palencia, Europhys. Lett. {\bf 99}, 50003 (2012)\\ {[5]} D. Delande and G. Orso, Phys. Rev. Lett. {\bf 113}, 060601 (2014) [Preview Abstract] |
Tuesday, May 24, 2016 3:00PM - 3:30PM |
C3.00003: Direct weak localization signature with ultracold atoms: the CBS revival Invited Speaker: Vincent Josse Ultracold atomic systems in presence of disorder have attracted a lot of interest over the past decade, in particular to study the physics of Anderson localization (AL) in a renewed perspective. Landmark experiments have been demonstrated, in 1D \cite{Billy,Roati} and 3D \cite{Kondov,Jendrzejewskia,Semeghini} geometries. However many challenges remain and new ideas have emerged, as for instance the search for original signatures of Anderson localization in momentum space \cite{Karpiuk}. \\ Here I will describe our progresses along that line where a weak localization effect has been directly observed, i.e. the Coherent Backscattering (CBS) phenomenon \cite{Jendrzejewskib}. In particular I will report on the recent observation of suppression and revival of CBS when a controlled dephasing kick is applied to the system \cite{Muller}. This observation demonstrates a novel and general method, introduced by T. Micklitz and coworkers \cite{Micklitz}, to study probe phase coherence in disordered systems by manipulating time reversal symmetry. J. Billy \textit{et al.,}, Nature \textbf{453}, 891 (2008). G. Roati \textit{et al.,}, Nature \textbf{453}, 895 (2008). S. Kondov \textit{et al.,} Science \textbf{334}, 66 (2011). F. Jendrzejewki \textit{et al.,} \textit{Nat. Phys. }\textbf{8}, 398 (2012). S. Semeghini \textit{et al.} \textit{Nat. Phys. }\textbf{11}, 554 (2015). T. Karpiuk \textit{et al.}, \textit{Phys. Rev. Lett.} \textbf{109,} 190601 (2012). F. Jendrzejewski \textit{et al., Phys. Rev. Lett. }\textbf{109}, 195302 (2012). K. M\"{u}ller \textit{et al., Phys. Rev. Lett.} \textbf{114}, 205301 (2015). T. Micklitz\textit{ et al}., \textit{Phys. Rev. B} \textbf{91}, 064203 (2015). [Preview Abstract] |
Tuesday, May 24, 2016 3:30PM - 4:00PM |
C3.00004: Anderson localization and beyond with disordered quantum gases Invited Speaker: Giovanni Modugno Ultracold atoms in disordered optical potentials allow to simulate fundamental aspects of the physics of disordered quantum systems. Employing non interacting atoms we have been able to verify the existence of the mobility edge in 3D predicted by P.W. Anderson more than 50 years ago. We are currently exploring the complex phases that arise in presence of disorder, interactions and finite temperature. [Preview Abstract] |
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