Superfluidity of quasi-2D He-4 droplets on graphite

TL;DR

This study uses computer simulations to explore superfluidity in nanoscale quasi-2D He-4 droplets on graphite, revealing size-dependent phases and superfluid behavior at ultra-low temperatures.

Contribution

It provides new insights into the size-dependent superfluid and solid phases of He-4 droplets on graphite, including the emergence of a 1D Luttinger liquid at the surface.

Findings

Clusters of ~20 atoms are fully superfluid.

Larger clusters develop a crystalline core with a superfluid surface.

Superfluidity persists at temperatures below 0.15 K.

Abstract

The superfluid response of nanoscale size quasi-2D He-4 droplets adsorbed on a graphite substrate is investigated by computer simulations. It is found that clusters comprising as few as 7 atoms are stable at temperatures lower than < 0.15 K. Clusters of ~20 atoms or less are liquid-like and ~100% superfluid. As the size is increased, the central region crystallizes, forming the commensurate C_1/3 phase, with a surface sliver of superfluidity evolving into a perimetral 1D Luttinger liquid with increasing cluster size. The relevance to quasi-2D molecular spectroscopy and to transverse quantum superfluidity is discussed.