Observation of thermo-mechanical equilibration in the presence of a solid 4He conduit

TL;DR

This study demonstrates a thermo-mechanical effect in solid helium-4, showing that a temperature difference induces a pressure difference consistent with superfluid helium behavior, confirming flux-limited flow below 600 mK.

Contribution

First experimental observation of thermo-mechanical equilibration in solid helium-4 with a quantitative match to superfluid helium effects.

Findings

Pressure difference grows with temperature difference in solid helium.

Flow through solid helium is flux-limited below 600 mK.

Thermo-mechanical effect aligns with superfluid helium predictions.

Abstract

We observe a thermo-mechanical effect when a chemical potential difference is created by a temperature difference imposed between two liquid reservoirs connected to each other through Vycor rods in series with solid hcp 4He. By creating a temperature difference, $\Delta T$, between the two reservoirs, we induce a rate-limited growth of a pressure difference between the two reservoirs, $\Delta P$. In equilibrium $\Delta P {\it vs.} \Delta T$ is in quantitative agreement with the thermo-mechanical effect in superfluid helium. These observations confirm that below $\sim$ 600 mK a flux-limited flow exists through the solid helium.