Abstract
We discuss different ways to produce liquid hydrogen at temperatures below its normal freezing temperature, where it can enter a superfluid state. Our consideration is based on the fact that solid and liquid phases may coexist in equilibrium at different pressures. To provide this pressure difference we take a look at the effect of a one-sided mechanical pressure on the solid phase and an external electrical field. We calculate thermodynamical functions for hydrogen both in stable and metastable domains, and its phase diagram, and find a domain of possible superfluidity, using a semiempirical thermodynamical model and recent data on critical temperatures of Bose liquids. We estimate both the value of the excess pressure on solid hydrogen and the electrical field strength necessary to stabilize the superfluid domain.