Propagation of collective pair excitations in disordered Bose superfluids

TL;DR

This paper investigates how disorder affects the propagation of collective excitations in a disordered Bose superfluid, revealing complex localization behavior and mobility spectra influenced by disorder, screening, and density depletion.

Contribution

It introduces a meanfield approach incorporating local density depletion and formulates the transport as a screened scattering problem, uncovering a non-monotonic energy dependence of disorder effects.

Findings

Disorder causes a non-monotonic energy dependence of the disorder parameter.

Four classes of mobility spectra with varying mobility edges are identified.

Implications for experiments with disordered ultracold atoms are discussed.

Abstract

We study the effect of disorder on the propagation of collective excitations in a disordered Bose superfluid. We incorporate local density depletion induced by strong disorder at the meanfield level, and formulate the transport of the excitations in terms of a screened scattering problem. We show that the competition of disorder, screening, and density depletion induces a strongly non-monotonic energy dependence of the disorder parameter. In three dimensions, it results in a rich localization diagram with four different classes of mobility spectra, characterized by either no or up to three mobility edges. Implications on experiments with disordered ultracold atoms are discussed.