Vacancy supersolid of hard-core bosons on the square lattice

TL;DR

This paper investigates the phase diagram of hard-core bosons on a square lattice, revealing vacancy-induced supersolid phases with specific ordering patterns through Quantum Monte Carlo simulations.

Contribution

It identifies new vacancy supersolid phases with star and stripe orderings, expanding understanding of quantum phases in lattice boson systems.

Findings

Vacancy supersolid with star ordering found below quarter filling

Supersolid phase exists between star and stripe phases above quarter filling

No supersolid phase above quarter filling if half-filling state is crystal or superfluid

Abstract

The ground state of hard-core bosons on the square lattice with nearest and next-nearest neighbor repulsion is studied by Quantum Monte Carlo simulations. A supersolid phase with vacancy condensation and 'star' diagonal ordering is found for filling less than a quarter. At fillings above one quarter, a supersolid phase exists between the star and the stripe crystal at half-filling. No supersolid phase occurs above quarter-filling, if the ground state at half-filling is either a checkerboard crystal or a superfluid. No commensurate supersolid phase is observed.