Bosons in a double-well potential: Understanding the interplay between disorder and interaction in a simple model

TL;DR

This paper introduces an exactly solvable model of interacting bosons in a double-well potential with disorder, revealing how combined disorder and interaction can enhance phase coherence, contrary to their individual effects.

Contribution

The study presents a simple, exactly solvable model that captures the interplay between disorder and interaction in bosonic systems, explaining phenomena observed in complex models and experiments.

Findings

Disorder and interaction together enhance phase coherence.

The model reproduces features of the disordered Bose-Hubbard model.

Finite temperature results align with experimental observations.

Abstract

We propose an exactly solvable model to reveal the physics of the interplay between interaction and disorder in bosonic systems. Considering interacting bosons in a double-well potential, in which disorder is mimicked by taking the energy level mismatch between the two wells to be randomly distributed, we find "two negatives make a positive" effect. While disorder or interaction by itself suppresses the phase coherence between the two wells, both together enhance the phase coherence. This model also captures several striking features of the disordered Bose-Hubbard model found in recent numerical simulations. Results at finite temperatures may help explain why a recent experiment did not find any evidence for the enhancement of phase coherence in a disordered bosonic system.