Local Superfluidity of Parahydrogen Clusters

TL;DR

This study uses Quantum Monte Carlo simulations to investigate the local superfluid response of small parahydrogen clusters at ultra-low temperatures, revealing uniform superfluidity throughout the clusters rather than confinement at the surface.

Contribution

It demonstrates that superfluidity in small parahydrogen clusters is uniform and involves long exchange cycles, challenging previous claims of surface-confined superfluidity.

Findings

Superfluidity is uniform throughout the clusters.

Superfluidity involves long exchange cycles.

Clusters with shell structure are essentially superfluid.

Abstract

We study by Quantum Monte Carlo simulations the local superfluid response of small (up to 27 molecules) parahydrogen clusters, down to temperatures as low as 0.05 K. We show that at low temperature superfluidity is not confined at the surface of the clusters, as recently claimed by Khairallah et al. [Phys. Rev. Lett. 98, 183401 (2007)]. Rather, even clusters with a pronounced shell structure are essentially uniformly superfluid. Superfluidity occurs as a result of long exchange cycles involving all molecules.