The fate of vacancy-induced supersolidity in 4He

TL;DR

This paper uses quantum Monte Carlo simulations to investigate vacancy-induced supersolidity in solid 4He, finding vacancies tend to separate rather than induce superflow, but non-equilibrium vacancies on defects might explain experimental results.

Contribution

The study provides the first computational evidence that vacancies in 4He crystals do not promote supersolidity but suggests non-equilibrium vacancies could account for experimental observations.

Findings

Vacancies in 4He tend to separate instead of forming a supersolid.

Non-equilibrium vacancies on defects may explain experimental supersolid signals.

Vacancy-induced superflow is unlikely in ideal 4He crystals.

Abstract

The supersolid state of matter, exhibiting non-dissipative flow in solids, has been elusive for thirty five years. The recent discovery of a non-classical moment of inertia in solid 4He by Kim and Chan provided the first experimental evidence, although the interpretation in terms of supersolidity of the ideal crystal phase remains subject to debate. Using quantum Monte Carlo methods we investigate the long-standing question of vacancy-induced superflow and find that vacancies in a 4He crystal phase separate instead of forming a supersolid. On the other hand, non-equilibrium vacancies relaxing on defects of poly-crystalline samples could provide an explanation for the experimental observations.