Phases of lattice hard core bosons in a periodic superlattice

TL;DR

This paper investigates the phase diagram of lattice hard core bosons with repulsive interactions under a superlattice, revealing crystal, supersolid, and superfluid phases through Quantum Monte Carlo simulations.

Contribution

It provides new insights into the phase behavior of hard core bosons in a superlattice, including the existence of supersolid phases, which were not well understood before.

Findings

Crystal phases aligned with the adsorption lattice.

Existence of supersolid phases on vacancy and interstitial sides.

Superfluid density vanishes at commensuration.

Abstract

We study by Quantum Monte Carlo simulations the phase diagram of lattice hard core bosons with nearest-neighbour repulsive interactions, in the presence of a super-lattice of adsorption sites. For a moderate adsorption strength, the system forms crystal phases registered with the adsorption lattice; a "supersolid" phase exists, on both the vacancy and interstitial sides, whereas at commensuration the superfluid density vanishes. The possible relevance of these results to experiments on $^4$He films adsorbed on graphite is discussed.