Phase diagram of 4He adsorbed on graphite

TL;DR

This study uses the continuous space worm algorithm to explore the phase diagram of 4He films on graphite, revealing various phases in the first and second layers and clarifying the conditions for their stability.

Contribution

It provides a detailed theoretical analysis of 4He on graphite, identifying specific phases and the impact of zero-point fluctuations on phase stability.

Findings

First layer has domain-wall and (7/16) registered phases.

Second layer exhibits superfluid and incommensurate solid phases.

No evidence of supersolid phase was observed.

Abstract

We present results of a theoretical study of 4He films adsorbed on graphite, based on the continuous space worm algorithm. In the first layer, we find a domain-wall phase and a (7/16) registered structure between the commensurate (1/3) and the incommensurate solid phases. For the second layer, we find only superfluid and incommensurate solid phases. The commensurate phase found in previous simulation work is only observed if first layer particles are kept fixed; it disappears upon explicitly including their zero-point fluctuations. No evidence of any "supersolid" phase is found.