Mass flux and solid growth in solid 4He: 60 mK - 700 mK

TL;DR

This study investigates mass flux and solid growth in helium-4 at temperatures between 60 mK and 700 mK, revealing temperature-dependent flux behavior and solid growth limitations.

Contribution

It demonstrates the temperature dependence of atom flux in solid helium-4 and identifies a flux drop near 80 mK, providing new insights into solid helium behavior.

Findings

DC atom flux occurs below 600 mK

Flux drops abruptly near 80 mK

Solid growth and density addition depend on initial temperature

Abstract

We use the thermo-mechanical effect to create a chemical potential difference between two liquid reservoirs connected to each other through Vycor rods in series with solid hcp 4He to confirm that a DC flux of atoms takes place below 600 mK, but find that the flux falls abruptly in the vicinity of 80 mK. It is impossible to add density to a solid freshly made at 60 mK and samples freshly made at 60 mK do not allow mass flux, even when raised in temperature to 200 mK. Solids created above 300 mK and cooled to 60 mK accept added density and demonstrate finite mass flux.