Superfluidity inH2Films

Path integral Monte Carlo calculations were used to study a 2D system of ${\mathrm{H}}_2$ molecules. The ground state on a flat substrate is a triangular lattice, a localized solid. We find that the introduction of some weakly attractive impurities (specifically alkali metal atoms) in the right concentration $\left(\sim 0.01{Å}^{-2\mathrm{}}\right)$ stabilizes a liquid hydrogen phase of concentration $0.04{Å}^{-2\mathrm{}}$ which undergoes a Kosterlitz-Thouless superfluid transition below approximately 1.2 K.