⁴He monolayer on graphene: a quantum Monte Carlo study

Abstract

We revisit the problem of adsorption of a single 4He layer on graphene, focusing on the commen-
surate (C 1/3) crystalline phase, specifically on whether it may possess a nonzero superfluid response,
and on the existence of superfluid phases, either (metastable) liquid or vacancy-doped crystalline.
We make use of canonical Quantum Monte Carlo simulations at zero and finite temperature, based
on a realistic microscopic model of the system. Our results confirm the absence of any superfluid
response in the commensurate crystal, and that no thermodynamically stable uniform phase exists at
lower coverage. No evidence of a possibly long-lived, metastable superfluid phase at C 1/3 coverage is
found. Altogether, the results of ground-state projection methods and finite-temperature simulations
are entirely consistent.