Seminar
Tuesday, 29 June, 2010
Group Seminar LMU: Anderson localization with ultracold atoms: from the 1D direct observation to the quantum simulation of the 3D transition
Tuesday, 29.06.2010 10 a.m. (s.t.) in H107, Fakultät für Physik LMU
Alain Bernard, Atom Optics group, Laboratoire Charles Fabry, Institut d'Optique
One of the main challenges of modern condensed matter physics is the understanding of the electronic quantum transport in a disordered medium at the mesoscopic scale. There, interferences originating from coherent random scattering can lead to suppression of transport; this is the so-called Anderson localization [1]. Despite huge experimental efforts, many important questions remain, such as the accurate value of the critical exponents of the Anderson metal-insulator phase transition, or the effects of interactions. For these studies, ultracold atomic systems reveal themselves a very adapted tool to mimic the phenomenon with higher control and tunability [2].
Two years ago, we demonstrated the possibility to observe directly Anderson localization of 1D matterwaves, in an optically created correlated disorder [3]. In this geometry, even though all states should be localized, effective mobility edges appear due to the correlated nature of the disorder. This involves a crossover between different steady states, which has been experimentally observed.
This experiment paved the way for further studies: localization of interacting 1D matterwaves have been realized recently [4, 5] and our group is now focusing on the higher dimension cases [6]. In my talk, I will give you the key features and the most recent progresses of the experiment we are now carrying out, which aims to observe directly the Anderson transition expected in the 3D geometry. As the dynamic of localization is expected to be very slow, we have implemented a magnetic levitation system that might allow us to observe time of flights of several seconds. I will also show you that the experiment requires large numerical apertures to be performed, since the design of the disordered potential is much more critical than for the 1D case.
[1] Anderson, P. W., Absence of Diffusion in Certain Random Lattices, Phys. Rev. 109, 1492 (1958)
[2] Sanchez-Palencia, L. & Lewenstein, M., Disordered quantum gases under control, Nat. Phys. 6, 87 (2010)
[3] Billy, J.; Josse, V.; Zuo, Z.; Bernard, A.; Hambrecht, B.; Lugan, P.; Clément, D.; Sanchez-Palencia, L.; Bouyer, P. & Aspect, A., Direct Observation of Anderson localization of matter-waves in a controlled disorder, Nature 453, 891 (2008)
[4] Deissler, B.; Zaccanti, M.; Roati, G.; D'Errico, C.; Fattori, M.; Modugno, M.; Modugno, G. & Inguscio, M., Delocalization of a disordered bosonic system by repulsive interactions, Nat. Phys., 6, 354 (2010)
[5] Dries, D.; Pollack, S. E.; Hitchcock, J. M. & Hulet, R. G, Dissipative Transport of a Bose-Einstein Condensate, arXiv, 1004:1891v1 (2010)
[6] Robert-de-Saint-Vincent, M.; Brantut, J.-P.; Allard, B.; Plisson, T.; Pezze, L.; Sanchez-Palencia, L.; Aspect, A.; Bourdel, T. & Bouyer, P., Anisotropic 2D diffusive expansion of ultra-cold atoms in a disordered potential, arXiv, 1004.0312v1 (2010)