Equilibrium phases of dipolar lattice bosons in the presence of random diagonal disorder

TL;DR

This study investigates how disorder and dipolar interactions influence the phases of two-dimensional lattice bosons, revealing the emergence of Bose glass and checkerboard solid phases through large-scale quantum Monte Carlo simulations.

Contribution

It provides the first detailed phase diagram of disordered dipolar lattice bosons, highlighting the stability of superfluidity and the formation of Bose glass and checkerboard phases.

Findings

Superfluidity is suppressed by weak disorder, leading to a Bose glass.

Superfluidity persists at certain interaction strengths despite disorder.

Checkerboard patterns emerge at high interactions with disorder-induced defects.

Abstract

Ultracold gases offer an unprecedented opportunity to engineer disorder and interactions in a controlled manner. In an effort to understand the interplay between disorder, dipolar interaction and quantum degeneracy, we study two-dimensional hard-core dipolar lattice bosons in the presence of on-site bound disorder. Our results are based on large-scale path-integral quantum Monte Carlo simulations by the Worm algorithm. We study the ground state phase diagram at fixed half-integer filling factor for which the clean system is either a superfluid at lower dipolar interaction strength or a checkerboard solid at larger dipolar interaction strength. We find that, even for weak dipolar interaction, superfluidity is destroyed in favor of a Bose glass at relatively low disorder strength. Interestingly, in the presence of disorder, superfluidity persists for values of dipolar interaction strength for which the clean system is a checkerboard solid. At fixed disorder strength, as the dipolar interaction is increased, superfluidity is destroyed in favor of a Bose glass. As the interaction is further increased, the system eventually develops extended checkerboard patterns in the density distribution. Due to the presence of disorder, though, grain boundaries and defects, responsible for a finite residual compressibility, are present in the density distribution. Finally, we study the robustness of the superfluid phase against thermal fluctuations.