3He adsorbed on molecular hydrogen surfaces

TL;DR

This study uses diffusion Monte Carlo simulations to explore the phase diagram of 3He adsorbed on molecular hydrogen surfaces, revealing a stable 2D gas phase and its relation to commensurate structures, aligning well with experimental data.

Contribution

First detailed quantum Monte Carlo analysis of 3He on molecular hydrogen surfaces, identifying stable phases and their structural properties.

Findings

2D helium gas spans from dilute to specific density

Gas is in equilibrium with a 7/12 commensurate structure

Results align with experimental observations

Abstract

Using a diffusion Monte Carlo (DMC) technique, we calculated the phase diagram of 3He adsorbed on a first solid layer of a molecular hydrogen isotope (H2,HD and D2) on top of graphite. The results are qualitatively similar in all cases: a two-dimensional gas spanning from the infinite dilution limit to a second-layer helium density of 0.048 +/- 0.004 Ang^{-2}. That gas is in equilibrium with a 7/12 commensurate structure, more stable than any incommensurate triangular solid of similar density. These findings are in reasonably good agreement with available experimental data.