Quasi-2D $$\hbox {H}_2$$: On the Verge of Turning Superfluid?

Abstract

First principle computer simulations of a thin parahydrogen film adsorbed on a silica substrate at low temperature (below 6 K) yield no evidence that the top layer is liquid and/or in the proximity of a superfluid transition, as claimed in recent experimental work (Makiuchi et al. in Phys Rev Lett 123:245301, 2019). Computed values of first and second layer completion densities are in quantitative agreement with experiment, but as observed also on other substrates, the top layer is an insulating crystal, quantum-mechanical exchanges of molecules are non-existent, and the overall physical behavior of the system can be understood largely along classical lines.