Dislocation induced anomalous softening of solid helium

TL;DR

This paper proposes that dislocation motion in solid helium causes elastic anomalies and softening of the shear modulus, providing a dislocation-based explanation for observed behaviors traditionally linked to supersolidity.

Contribution

It introduces a dislocation motion model that explains elastic softening and dissipation in solid helium without invoking supersolidity.

Findings

Dislocation glide causes strong temperature-dependent softening of shear modulus.

The model reproduces stress-strain behavior and work hardening rate observed experimentally.

Dislocation motion leads to dissipation peaks consistent with experimental observations.

Abstract

The classical motion of gliding dislocation lines in slip planes of crystalline solid helium leads to plastic deformation even at temperatures far below the Debye temperature and can affect elastic properties. In this work we argue that the gliding of dislocations and plasticity may be the origin of many observed elastic anomalies in solid He-4, which have been argued to be connected to supersolidity. We present a dislocation motion model that describes the stress-strain $\tau$-$\epsilon$ curves and work hardening rate $d\tau/d\epsilon$ of a shear experiment performed at constant strain rate $\dot{\epsilon}$ in solid helium. The calculated $d\tau/d\epsilon$ exhibits strong softening with increasing temperature due to the motion of dislocations, which mimics anomalous softening of the elastic shear modulus $\mu$. In the same temperature region the motion of dislocations causes dissipation with a prominent peak.