Anomalously Small Excitation Gaps as a Precursor of Dislocation Core Superfluidity in Solid Helium-4

TL;DR

This paper investigates how dislocations in solid helium-4 near a quantum phase transition support tiny excitation gaps, which could be observed through thermoactivation effects and ultrasound absorption, indicating a precursor to dislocation core superfluidity.

Contribution

It reveals the presence of anomalously small excitation gaps in dislocation cores of solid helium-4 near a quantum phase transition using Worm Algorithm simulations and visualization techniques.

Findings

Small excitation gaps detected via thermoactivation behavior.

Dislocations associated with these gaps visualized in simulations.

Potential experimental observation through ultrasound absorption.

Abstract

In the vicinity of the insulator-to-superfluid quantum phase transition in its core, a dislocation in a He-4 crystal supports particle-hole excitations with arbitrary small gaps. These exotic analogs of Frenkel interstitial-vacancy pairs should manifest themselves in various threshold and thermoactivation effects. In Worm Algorithm simulations, we reveal the presence of corresponding small gaps via anomalous thermoactivation behavior of particle number fluctuations, which we unambiguously associate with dislocations by "visualization" techniques. Experimentally, the related threshold and thermoactivation dependencies could be observed in the ultrasound absorption.