Mass flux and solid growth in solid He4 for 60-700 mK

Abstract

We use the thermomechanical effect to confirm that a flux of atoms takes place in hcp solid He4 below ∼600mK. We find that the flux falls abruptly in the vicinity of 80mK and rises with further reduction of temperature. Samples freshly made at 60mK do not allow mass flux and cannot be grown off the melting curve even when raised in temperature to 200mK. Solids created above ∼300mK and cooled to 60mK can be grown further and demonstrate finite mass flux. ©2010 The American Physical Society.