Anomaly of the Internal Friction in the Helium Crystals Grown in the Burst-like Growth Mode

TL;DR

This study investigates the internal friction in helium crystals grown in slow and burst-like modes, revealing additional damping and softening effects with a relaxation time of about 3ms, and discusses their possible origins.

Contribution

It presents new measurements of internal friction in helium crystals grown in different modes, highlighting anomalous effects specific to burst-like growth.

Findings

Additional damping and softening observed in burst-like growth

Relaxation to equilibrium occurs within approximately 3 milliseconds

Differences in internal friction between growth modes are identified

Abstract

The internal friction in the crystals grown in two modes, namely, slow and anomalously fast (burst-like growth) modes, is measured in the temperature range 0.49-0.75K at a frequency of about 75kHz. An additional contribution to the damping decrement and softening of the dynamic modulus are detected, and their relaxation to equilibrium values at a time constant of about 3ms is observed. Possible origins of this effect are discussed.