paper

Exchange-driven self-diffusion of nanoscale crystalline parahydrogen clusters on graphite

arXiv:2508.10883 · doi:10.1063/5.0299668

Abstract

Computer simulations yield evidence of superfluid behavior of nanoscale size clusters of parahydrogen adsorbed on a graphite substrate at low temperature (). Clusters with a number of molecules between 7 and 12 display concurrent superfluidity and crystalline order, reflecting the corrugation of the substrate. Remarkably, it is found that specific clusters with a number of molecules ranging between 7 and 12 self-diffuse on the surface like free particles, despite the strong pinning effect of the substrate. This effect is underlain by coordinated quantum-mechanical exchanges of groups of identical molecules, i.e., it has no classical counterpart.

6 pages, 4 figures

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