12,000

We have over 12,000 students, from over 100 countries, within one of the safest campuses in the UK

93%

93% of Lancaster students go into work or further study within six months of graduating

Home > Research > Publications & Outputs > Experiments on the rapid mechanical expansion o...
View graph of relations

« Back

Experiments on the rapid mechanical expansion of liquid 4He through its superfluid transition.

Research output: Contribution to journalJournal article

Published

Journal publication date16/11/2006
JournalPhysical Review E
Journal number5
Volume74
Pages056305
Original languageEnglish

Abstract

Phenomena following a rapid mechanical quench of liquid 4He from its normal to its superfluid phase are reported and discussed. The mechanical expansion apparatus is an improved version of that described previously. It uses a double-cell geometry to effect a partial separation of the sample from the convolutions of the bellows that form the outer wall of the cell. Consistent with earlier work, no evidence is found for the production of quantized vortices via the Kibble-Zurek (KZ) mechanism. Although the expansion is complete within 15 ms, the second-sound velocity and attenuation continue to increase for a further ∼60 ms; correspondingly the temperature decreases. Subsequently, the temperature rises again toward its final value as the second-sound velocity and attenuation decrease. It is shown that this unexpected behavior is apparently associated with a large-amplitude second-sound oscillation produced by the expansion, and it is suggested that the observed vortices are created by the normal fluid–superfluid counterflow that constitutes the second-sound wave. If production of large-amplitude second sound is inherent to the mechanical expansion of liquid 4He through the superfluid transition, as appears to be the case for final temperatures more than 3 mK from the λ transition, the phenomenon sets a lower bound on the density of KZ vortices that can be detected in this type of experiment.