Equation of State of Overpressurized Liquid 4He at Zero Temperature

In recent experiments, Balibar and collaborators have been able to produce metastable superfluids 4He up to 163 ± 20 bar, a pressure much higher than the freezing point (25 bar). Interpretation of some of their experimental data requires the knowledge of the equation of state of bulk 4He in this high-pressure regime. As this is not experimentally known, they extrapolate to these high pressures using analytical fits to the well-known equation of state in the stable regime. Using the same theoretical analysis that allowed in the past to reproduce accurately the equation of state of liquid 4He in the stable domain, we present now extended results for this equation of state up to ∼ 350 bar. Our calculations, based on the diffusion Monte Carlo method, show some significant differences with the proposed extrapolations, which could be relevant for future experiments.