Scientific Results

Transport of an interacting Bose gas in 1D disordered lattices

Year: 2014

Authors: D’Errico C., Chaudhuri S., Gori L., Kumar A., Lucioni E., Tanzi L., Inguscio M., Modugno G.

Autors Affiliation: LENS and Dipartimento di Fisica e Astronomia, Università di Firenze, and CNR-INO 50019 Sesto Fiorentino, Italy

Abstract: We use ultracold atoms in a quasiperiodic lattice to study two outstanding problems in the physics of disordered
systems: a) the anomalous diffusion of a wavepacket in the presence of disorder, interactions and noise; b) the transport
of a disordered superfluid. a) Our results show that the subdiffusion, observed when interaction alone is present, can be
modelled with a nonlinear diffusion equation and the peculiar shape of the expanding density profiles can be connected to the
microscopic nonlinear diffusion coefficients. Also when noise alone is present we can describe the observed normal diffusion
dynamics by existing microscopic models. In the unexplored regime in which noise and interaction are combined, instead, we
observe an anomalous diffusion, that we model with a generalized diffusion equation, where noise- and interaction-induced
contributions add each other. b) We find that an instability appearing at relatively large momenta can be employed to locate
the fluid-insulator crossover driven by disorder. By investigating the momentum-dependent transport, we observe a sharp
crossover from a weakly dissipative regime to a strongly unstable one at a disorder-dependent critical momentum. The set of
critical disorder and interaction strengths for which such critical momentum vanishes, can be identified with the separation
between a fluid regime and an insulating one and can be related to the predicted zero-temperature superfluid-Bose glass

Conference title: 15th International Conference on
Transport in Interacting Disordered Systems

More Information: This work was supported by ERC ( grants 203479 and 247371) and by MIUR ( grants PRIN2009FBKLN and RBFR12NLNA).
KeyWords: Diffusion; Glass transition; Momentum; Partial differential equations, Disorder; Interaction; Noise; Out-of-equilibrium; Transport, Diffusion in liquids
DOI: 10.1063/1.4893506