Freezing and pressure-driven flow of solid helium in Vycor

TL;DR

This study investigates the flow and density changes of solid helium in Vycor to test for supersolid behavior, finding no evidence of pressure-driven flow that would indicate supersolidity.

Contribution

It provides direct measurements of helium density and flow in Vycor, setting upper limits on supersolid flow and clarifying previous torsional oscillator results.

Findings

No pressure-induced flow detected in Vycor pores.

Upper limit of 0.003 μm/s on supersolid flow.

Density measurements show no mass redistribution.

Abstract

The recent torsional oscillator results of Kim and Chan suggest a supersolid phase transition in solid He-4 confined in Vycor. We have used a capacitive technique to directly monitor density changes for helium confined in Vycor at low temperature and have used a piezoelectrically driven diaphragm to study the pressure-induced flow of solid helium into the Vycor pores. Our measurements showed no indication of a mass redistribution in the Vycor that could mimic supersolid decoupling and put an upper limit of about 0.003 um/s on any pressure-induced supersolid flow in the pores of Vycor.