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

Research output: Contribution to Journal/MagazineJournal articlepeer-review

<mark>Journal publication date</mark>1981
<mark>Journal</mark>Journal of Physics C: Solid State Physics
Pages (from-to)L681-L686
Publication StatusPublished
<mark>Original language</mark>English


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.