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

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 supersolidphase 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.

Automated summary

The second layer of 4He adsorbed on a graphite substrate is studied using Quantum Monte Carlo simulations. The substrate's corrugation is fully taken into account in a microscopic model, and the results are compared to those obtained with a smooth substrate. The main effect of the corrugation is a 20% reduction in the superfluid fraction of the top layer at zero temperature. No evidence of any commensurate (7/12) crystalline and/or supersolid phase is found, and the superfluid transition temperature is estimated to be -0.75 K. The implications of these findings on recent experiments are discussed.