Proton pairing, electron pairing, and the phase structure of dense hydrogen

Dense hydrogen can be viewed as the superimposition of two standard many-body problems, namely those of the interacting electron gas and the corresponding interacting proton gas, taken at equal average densities. The known low-density instability towards proton pairing appears to be preserved to about as inferred from a determination of electronic total energies. Prior to this in density, a transition to a metallic state occurs in which proton pairing persists. In this band-overlap state, electron pairing via a phonon and electronic mechanism is predicted to occur with a transition temperature higher than that found for the eventual monatomic state. This phase is itself preceded by one where electronic symmetry is broken at low temperatures resulting in a state of spontaneous polarization.