Inversion of coherent backscattering with interacting Bose-Einstein condensates in two-dimensional disorder : a Truncated Wigner approach

TL;DR

This paper investigates how interactions in a Bose-Einstein condensate affect coherent backscattering in a disordered 2D system, revealing an inversion of the backscattering cone and the persistence of weak antilocalisation effects.

Contribution

It introduces a Truncated Wigner simulation approach to study interaction effects on coherent backscattering, extending beyond mean-field approximations.

Findings

Inversion of the coherent backscattering cone with non-zero interactions.

Dephasing suppresses the antilocalisation signature at high densities.

Weak antilocalisation persists at finite interactions, suggesting experimental observability.

Abstract

We theoretically study the propagation of an interacting Bose-Einstein condensate in a two-dimensional disorder potential, following the principle of an atom laser. The constructive interference between time-reversed scattering paths gives rise to coherent backscattering, which may be observed under the form of a sharp cone in the disorder-averaged angular backscattered current. As is found by the numerical integration of the Gross-Pitaevskii equation, this coherent backscattering cone is inversed when a non-vanishing interaction strength is present, indicating a crossover from constructive to destructive interferences. Numerical simulations based on the Truncated Wigner method allow one to go beyond the mean-field approach and show that dephasing renders this signature of antilocalisation hidden behind a structureless and dominant incoherent contribution as the interaction strength is increased and the injected density decreased, in a regime of parameters far away from the mean-field limit. However, despite a partial dephasing, we observe that this weak antilocalisation scenario prevails for finite interaction strengths, opening the way for an experimental observation with $^{87}$Rb atoms.