Enhanced transport of spin-orbit coupled Bose gases in disordered potentials

TL;DR

This paper demonstrates that spin-orbit coupling combined with a Zeeman field in Bose gases reduces disorder effects, increasing localization length and conductivity, as shown through theoretical analysis and numerical simulations.

Contribution

It reveals how SOC and Zeeman fields suppress back scattering in disordered Bose gases, enhancing transport properties, a novel insight into disorder manipulation in quantum gases.

Findings

SOC suppresses back scattering in disordered Bose gases.

States in the SOC gap exhibit negligible back-scattering.

Without SOC, states rapidly localize in disorder.

Abstract

Anderson localization is a single particle localization phenomena in disordered media that is accompanied by an absence of diffusion. Spin-orbit coupling (SOC) describes an interaction between a particle's spin and its momentum that directly affects its energy dispersion, for example creating dispersion relations with gaps and multiple local minima. We show theoretically that combining one-dimensional spin-orbit coupling with a transverse Zeeman field suppresses the effects of disorder, thereby increasing the localization length and conductivity. This increase results from a suppression of back scattering between states in the gap of the SOC dispersion relation. Here, we focus specifically on the interplay of disorder from an optical speckle potential and SOC generated by two-photon Raman processes in quasi-1D Bose-Einstein condensates. We first describe back-scattering using a Fermi's golden rule approach, and then numerically confirm this picture by solving the time-dependent 1D Gross Pitaevskii equation for a weakly interacting Bose-Einstein condensate with SOC and disorder. We find that on the 10's of millisecond time scale of typical cold atom experiments moving in harmonic traps, initial states with momentum in the zero-momentum SOC gap evolve with negligible back-scattering, while without SOC these same states rapidly localize.