Phase diagrams, critical and multicritical behavior of hard-core Bose-Hubbard models

TL;DR

This paper maps the phase diagram of the hard-core Bose-Hubbard model on a square lattice, revealing various supersolid phases, quantum critical points, and multicritical behaviors influenced by interaction strengths.

Contribution

It introduces a comprehensive mean-field and spin-wave analysis of the model, identifying new phases and critical behaviors not previously characterized.

Findings

Multiple supersolid phases stabilized by interactions

Identification of new quantum critical points

Three distinct phase diagram topologies

Abstract

We determine the zero-temperature phase diagram of the hard-core Bose-Hubbard model on a square lattice by mean-field theory supplemented by a linear spin-wave analysis. Due to the interplay between nearest and next-nearest neighbor interaction and cubic anisotropy several supersolid phases with checkerboard, stripe domain or intermediate symmetry are stabilized. The phase diagrams show three different topologies depending on the relative strength of nearest and next-nearest neighbor interaction. We also find a rich variety of new quantum critical behavior and multicritical points and discuss the corresponding effective actions and universality classes.