Mechanical and superfluid properties of dislocations in solid He4

TL;DR

This paper investigates the mechanical and superfluid behaviors of dislocations in solid helium-4, proposing mechanisms for observed shear modulus softening and superfluid suppression related to temperature-dependent dislocation interactions.

Contribution

It introduces a theoretical framework explaining dislocation smoothness at zero temperature and the temperature-induced softening and superfluid suppression in solid helium-4.

Findings

Dislocations are smooth at zero temperature due to Coulomb-like interactions.

Finite temperature causes roughening of dislocations, softening the shear modulus.

Thermal kinks suppress superfluidity along dislocation cores.

Abstract

Dislocations are shown to be smooth at zero temperature because of the effective Coulomb-type interaction between kinks. Crossover to finite temperature rougnehing is suggested to be a mechanism responsible for the softening of \he4 shear modulus recently observed by Day and Beamish (Nature, {\bf 450}, 853 (2007)). We discuss also that strong suppresion of superfuidity along the dislocation core by thermal kinks can lead to locking in of the mechanical and superfluid responses.