Supersolid Helium at High Pressure

TL;DR

This study investigates how the supersolid fraction of helium varies with pressure, revealing a peak around 55 bar and decreasing to zero near 170 bar, using torsional oscillator measurements.

Contribution

It provides the first detailed pressure dependence of the supersolid fraction in helium, identifying a maximum and the pressure at which supersolidity vanishes.

Findings

Supersolid fraction increases from 0.6% to 1.5% with pressure.

Maximum supersolid fraction occurs near 55 bar.

Supersolidity disappears near 170 bar.

Abstract

We have measured the pressure dependence of the supersolid fraction by a torsional oscillator technique. Superflow is found from 25.6 bar up to 136.9 bar. The supersolid fraction in the low temperature limit increases from 0.6 % at 25.6 bar near the melting boundary up to a maximum of 1.5% near 55 bar before showing a monotonic decrease with pressure extrapolating to zero near 170 bar.