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Temperature-dependent vortex nucleation in isotopically pure superfluid 4He.

Research output: Contribution to journalJournal article

Published

Journal publication date1981
JournalJournal of Physics C: Solid State Physics
Volume14
PagesL681-L686
Original languageEnglish

Abstract

We have investigated the temperature dependence of the rate nu which negative ions nucleate vortex rings in isotopically pure superfluid 4He. Measurements of nu(E,T) are presented for a pressure of 23 bar with electric fields E in 5.8 < E < 1.2 x l0^6 V m-l and temperatures T in 0.3 < T < 0.8 K. Provided that due allowance is made for the drag arising from ion-excitation scattering, (nu - nu0) is proportional to Nr, where Nr is the thermal roton density and nu0 is the temperature-dependent limiting value of nu below 0.5 K. We show that this discovery is consistent with the existence of an additional vortex nucleation mechanism, characterised by a critical velocity reduced by roton absorption, but ultimately determined by a requirement for the conservation of energy and momentum.