Superfluid response of parahydrogen clusters in superfluid He-4

TL;DR

This study uses first-principles simulations to demonstrate that small parahydrogen clusters in superfluid helium exhibit significant superfluidity at very low temperatures, with superfluid fractions increasing as temperature decreases.

Contribution

It provides the first detailed simulation-based evidence of superfluid response in parahydrogen clusters within superfluid helium, highlighting temperature-dependent behavior.

Findings

Superfluid fraction is about 44% at 0.25 K.

Superfluid fraction increases to 66% at 0.15 K.

Superfluid response is reduced compared to isolated clusters due to molecular localization.

Abstract

First principle computer simulations yield evidence of a finite superfluid response at low temperature of a parahydrogen cluster of 15 molecules in bulk superfluid He-4. The superfluid fraction is worth ~44% at T=0.25 K, growing to about 66% at T=0.15 K, i.e., it is substantially reduced compared to that of the same cluster in vacuo, due to higher molecular localization. The implications of these findings on the interpretation of experiments with linear molecules embedded in parahydrogen clusters immersed in superfluid helium are discussed.