Creation of Quantized Vortex Rings by Charge Carriers in Superfluid Helium

Vortex nucleation limited mobility of free electron bubbles in the Gross-Pitaevskii model of a superfluid

“…This is also in agreement with theoretical models proposed by Schwarz and Jang [39], and by Bowley [40] for the initial stages of the process of vortex nucleation. However, it appears that this scenario which is consistent with the mechanism depicted in Fig.…”

Macroscopic quantum tunneling of vortices in He II

“…2) in stronger electric fields (also observed in earlier work at higher pressures 11 ' 12 ) can be interpreted either as evidence for a complicated velocity dependence of TVo or, alternatively, as an indication that additional nucleation mechanisms come into play when the ionic velocity is large enough. Thus, the present data do not necessarily preclude the occurrence of, for example, axially symmetric nucleation processes, 16,22 even though the latter have associated critical velocities and energy barriers that are higher 26 than those for vortex loop creation.…”

Flux Creep, Pinning Potential and Critical Current Density in Bi2Sr2Ca1Cu2Ox Single Crystals

“…Under our experimental conditions, roton emission from the ion (Allum et al 1977) occurs very much more frequently than does the scattering of thermal rotons in the bath, and it is by no means evident through what mechanism the latter process might be able to influence the nucleation of vortex rings. If we try to interpret our data using the approach of Schwarz and Jang (1973) and Bowley (1976), we are forced to conclude either that the ionic instantaneous critical velocity decreases as T increases or that the attempt rate ( R in Bowley's paper) increases with ' T: Neither of these two possibilities was anticipated and neither seems particularly plausible.…”

“…In particular, it seemed that values of v measured for temperatures Tabove 0.9 K were an order of magnitude greater than the almost temperature-independent value found below 0.6 K. No such rapid temperature dependence had been anticipated on the basis of the nucleation model proposed by Schwarz and Jang (1973), or in the light of its subsequent extension by Bowley (1976). Unfortunately, however, the method used to measure v for T > 0 9 K differed from that used for T < 0.6 K and the intermediate range of temperatures could not be covered.…”

“…We note that (i) as pointed out by Donnelly and Roberts, the probability of finding a thermal roton in the right position close to the ion, and in the correct orientation for subsequent growth into a vortex ring, is far too small to account for the observed values of v; (ii) that the utility of the concept of localised roton states, introduced by Donnelly and Roberts to avoid this difficulty, appears to have been cast into considerable doubt by Schwarz and Jang (1973); (iii) that the experiments of Rayfield (1967), which provided the original stimulus for developing the peeling model of vortex creation have in any case been given an alternative and entirely satisfactory explanation (Zoll and Schwarz 1973). If the rotons are to be regarded as the proto-rings which, given the right conditions, can grow into fully fledged vortex rings, then it may be necessary to take explicit account of the rotons which are emitted by the ion itself.…”