Two-component Fermi-liquid theory: Equilibrium properties of liquid metallic hydrogen

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Abstract
Recent studies point to the possibility that condensed hydrogen will undergo a transition from an insulating molecular crystal phase to a metallic liquid phase at zero temperature and high pressure. Liquid metallic hydrogen (LMH) comprising interpenetrating proton and electron fluids, would constitute a two-component Fermi liquid having both long-range, species-dependent bare interactions and a very high component-mass ratio. We examine the low-temperature equilibrium properties of LMH (assuming that it is "normal") by means of a generalization to the case of two components of the phenomenological Landau Fermi-liquid theory. The general two-component formalism is discussed in some detail. Estimates for the relevant phenomenological Landau parameters for LMH are made, and results for low-temperature specific heat, compressibility, thermal expansion coefficient, and spin susceptibility are given. The specific heat and thermal expansion coefficient are found to be vastly greater in the liquid than in the corresponding solid due to the presence of proton quasiparticle excitations in the liquid. The possibility of a negative expansion coefficient of the liquid cannot be dismissed.