The solid phase of He-4: A Monte Carlo simulation study

TL;DR

This study uses Monte Carlo simulations to analyze the thermodynamics of solid helium-4 at very low temperatures, revealing temperature independence of key properties and minimal quantum exchanges, with results aligning with experimental data.

Contribution

It extends previous theoretical work by exploring lower temperatures, larger systems, and including quantum statistics effects in solid helium-4 simulations.

Findings

Thermodynamic properties are temperature-independent below 1 K.

Quantum exchanges are negligible even at 60 mK.

Results agree with experimental measurements within uncertainties.

Abstract

The thermodynamics of solid (hcp) He-4 is studied theoretically by means of unbiased Monte Carlo simulations at finite temperature, in a wide range of density. This study complements and extends previous theoretical work, mainly by obtaining results at significantly lower temperatures (down to 60 mK) and for systems of greater size, by including in full the effect of quantum statistics, and by comparing estimates yielded by different pair potentials. All the main thermodynamic properties of the crystal, e.g., the kinetic energy per atom, are predicted to be essentially independent of temperature below 1 K. Quantum-mechanical exchanges are virtually non-existent in this system, even at the lowest temperature considered. However, effects of quantum statistics are detectable in the momentum distribution. Comparison with available measurements shows general agreement within the experimental uncertainties.