The dipolar Bose-Hubbard model

TL;DR

This paper investigates a dipolar Bose-Hubbard model where bosons conserve both number and dipole moment, revealing novel phases like a Bose-Einstein insulator that combines insulating and condensate properties.

Contribution

It introduces and analyzes a dipolar Bose-Hubbard model demonstrating unique phases arising from dipole conservation, including a novel Bose-Einstein insulator phase.

Findings

Identification of gapped Mott insulators and gapless condensates.

Discovery of a Bose-Einstein insulator phase with simultaneous insulating and condensate features.

Analysis of phase transitions controlled by chemical potential and hopping strength.

Abstract

We study a simple model of interacting bosons on a d-dimensional cubic lattice whose dynamics conserves both total boson number and total boson dipole moment. This model provides a simple framework in which several remarkable consequences of dipole conservation can be explored. As a function of chemical potential and hopping strength, the model can be tuned between gapped Mott insulating phases and various types of gapless condensates. The condensed phase realized at large hopping strengths, which we dub a Bose-Einstein insulator, is particularly interesting: despite having a Bose condensate, it is insulating, and despite being an insulator, it is compressible.