Measurement of the Equation of State of Superfluid Helium-4 at Negative Pressure

Abstract

We report a measurement of the equation of state of superfluid 4 He (T ∼ 1 K) at negative pressure. A stimulated Brillouin gain spectrometer, used together with an optical interferometer, allows us to probe simultaneously both the compressibility and the density of acoustically driven metastable states of the liquid. In the pressure range 0 > P > −1 bar, the measured equation of state is in agreement with available theories.