Superfluid transition of the second layer of 4He on graphite: Does substrate corrugation matter?

Abstract

The second layer of 4He adsorbed on a graphite substrate is studied by Quantum Monte Carlo simulations. We make use of a microscopic model of the substrate fully accounting for its corrugation, and compare the results to those obtained with a smooth substrate. The only effect of corrugation is a ∼20% reduction of the value of the superfluid fraction of the top layer, in the limit of zero temperature. No evidence of any commensurate (7/12) crystalline and/or “supersolid” phase is found; the superfluid transition temperature is estimated to be ∼0.75 K. We discuss the implication of these findings on the interpretation of recent experiments.

Keywords

• Superfluidity
• Quantum Monte Carlo
• Helium films
• Kosterlitz–Thouless transition
• Supersolid