Quasi-2D Liquid He-3

TL;DR

This study uses quantum Monte Carlo simulations to demonstrate the existence of a stable, ultra-low density liquid He-3 monolayer on Alkali substrates, which may become superfluid at very low temperatures.

Contribution

It provides the first evidence of a thermodynamically stable quasi-2D liquid He-3 monolayer on Alkali substrates, highlighting the role of zero-point motion in its stability.

Findings

Stable liquid He-3 monolayer on Alkali substrates identified

Effective 2D density is approximately 0.02 Å⁻², the lowest in nature

Predicted superfluid transition temperature around 1 mK

Abstract

Quantum Monte Carlo simulations at zero temperature of an ensemble of He-3 atoms adsorbed on Mg and Alkali substrates yield strong evidence of a thermodynamically stable liquid He-3 monolayer on all Alkali substrates, with the possible exception of Li. The effective 2D density is close to 0.02$ inverse square Angstroms on Na, making it the lowest density liquid in Nature. Its existence is underlain by zero-point atomic motion perpendicular to the substrate, whose effect is softening the short-range repulsion of the helium interatomic potential. The monolayer films should turn superfluid at a temperature of order 1 mK. No liquid film is predicted to form on Mg, or on stronger substrates such as graphite.