Bose systems in spatially random or time-varying potentials

TL;DR

This paper explores how external random and time-varying potentials affect Bose systems, revealing transitions from extended condensates to granular states and normal glass, using a stochastic mean-field approach.

Contribution

It introduces a stochastic mean-field approximation to analyze Bose systems under spatially random and time-dependent potentials, highlighting phase transitions and nonequilibrium states.

Findings

Disorder causes Bose-Einstein condensate to fragment into granular regions.

Increasing disorder strength leads to a transition into a normal glass.

Time-dependent potentials can induce nonequilibrium granular condensates.

Abstract

Bose systems, subject to the action of external random potentials, are considered. For describing the system properties, under the action of spatially random potentials of arbitrary strength, the stochastic mean-field approximation is employed. When the strength of disorder increases, the extended Bose-Einstein condensate fragments into spatially disconnected regions, forming a granular condensate. Increasing the strength of disorder even more transforms the granular condensate into the normal glass. The influence of time-dependent external potentials is also discussed. Fast varying temporal potentials, to some extent, imitate the action of spatially random potentials. In particular, strong time-alternating potential can induce the appearance of a nonequilibrium granular condensate.