The low temperature elastic anomalies in solid helium

TL;DR

This paper investigates the elastic anomalies in solid helium at low temperatures, proposing a dislocation-based model that explains observed stiffening and inertia drops.

Contribution

It introduces a novel dislocation layer model that quantitatively explains low-temperature elastic anomalies in solid helium.

Findings

Model accounts for experimental elastic stiffening.

Model explains drops in rotational inertia.

Dislocation layers are key to anomalies.

Abstract

The elastic properties of hcp $^4$He samples have been shown to display various anomalies. The elastic shear modulus stiffens and the moment of rotational inertia drops when the temperature is lowered below $\sim$ 0.2 K. The relation between these two quantities is studied within the framework of classical deformable-body mechanics. A model based on the formation by plastic flow of extremely soft two-dimensional layers of dislocations is studied analytically and numerically. This model accounts quantitatively for a number of experiments. Other situations, in which it may seem less relevant, are discussed.