Bose-Einstein Condensates in Strongly Disordered Traps

TL;DR

This paper theoretically investigates Bose-Einstein condensates in combined harmonic and random potentials, revealing how disorder affects their size, shape, excitation energy, and stability, including fragmentation and metastability phenomena.

Contribution

It provides a semi-quantitative analysis of BEC behavior in disordered traps, highlighting the effects of disorder strength on condensate fragmentation and stability, and generalizing results to anisotropic traps.

Findings

Condensate fragments into Larkin-length-sized pieces under strong disorder.

Breathing mode frequency scales as inverse square of Larkin length.

Metastable condensate states can exist with negative scattering length.

Abstract

A Bose-Einstein condensate in an external potential consisting of a superposition of a harmonic and a random potential is considered theoretically. From a semi-quantitative analysis we find the size, shape and excitation energy as a function of the disorder strength. For positive scattering length and sufficiently strong disorder the condensate decays into fragments each of the size of the Larkin length ${\cal L}$. This state is stable over a large range of particle numbers. The frequency of the breathing mode scales as $1/{\cal L}^2$. For negative scattering length a condensate of size ${\cal L}$ may exist as a metastable state. These finding are generalized to anisotropic traps.