Ground-state Properties of a Supersolid in RPA

TL;DR

This paper analyzes the ground-state properties of a supersolid phase in a hard-core boson lattice model using RPA, highlighting the roles of vacancies, interstitials, and quantum fluctuations in phase stability.

Contribution

It provides a detailed RPA-based analysis of the supersolid phase, including all pair correlations and the effects of vacancies and interstitials, which is a novel approach.

Findings

Supersolid phase is stabilized by vacancies and interstitials.

Quantum fluctuations are crucial for the phase's properties.

Transition from superfluid to supersolid involves roton minimum collapse.

Abstract

We investigate the newly discovered supersolid phase by solving in random-phase approximation the anisotropic Heisenberg model of the hard-core boson ${}^4$He lattice at zero temperature. We include nearest and next-nearest neighbor interactions and calculate exactly all pair correlation functions in a cumulant decoupling scheme. We demonstrate the importance of vacancies and interstitials in the formation of the supersolid phase. The supersolid phase is characterised by strong quantum fluctuations which are taken into account rigorously. Furthermore we confirm that the superfluid to supersolid transition is triggered by a collapsing roton minimum however is stable against spontaneously induced superflow, i.e. vortex creation.