Phase Diagram of Interacting Bosons on the Honeycomb Lattice

TL;DR

This study uses quantum Monte Carlo simulations to explore the phase diagram of interacting bosons on a honeycomb lattice, revealing phase transitions from solid to superfluid and the emergence of supersolid phases with varying interaction strengths.

Contribution

It provides the first detailed quantum Monte Carlo analysis of phase transitions and supersolid phases in bosons on a honeycomb lattice, including effects of finite on-site repulsion.

Findings

Hard-core bosons exhibit a first-order transition from a solid to superfluid phase.

Supersolid phases appear when the bosons are soft-core, with superfluid density suppressed at large on-site repulsion.

No intermediate supersolid phase exists in the hard-core limit, only a direct transition.

Abstract

We study the ground state properties of repulsively interacting bosons on the honeycomb lattice using large-scale quantum Monte Carlo simulations. In the hard-core limit the half-filled system develops long ranged diagonal order for sufficiently strong nearest-neighbor repulsion. This staggered solid melts at a first order quantum phase transition into the superfluid phase, without the presence of any intermediate supersolid phase. Within the superfluid phase, both the superfluid density and the compressibility exhibit local minima near particle- (hole-) density one quarter, while the density and the condensate fraction show inflection points in this region. Relaxing the hard-core constraint, supersolid phases emerge for soft-core bosons. The suppression of the superfluid density is found to persist for sufficiently large, finite on-site repulsion.