Macroscopic quantum tunneling of vortices in He II

Abstract

Experimental evidence is presented showing that the creation of vortices in He II involves macroscopic quantum tunneling through, or thermal activation over, a potential-energy barrier e. The investigations, based on measurements of the rate at which negative ions create vortex rings in the isotopically pure superfluid within the temperature range 50 < T < 500 mK, have yielded a barrier height of e/kn^lA ± 0.1 K, in excellent agreement with the theoretical value predicted by Muirhead, Vinen, and Donnelly.

Observation of the turbulent flow in superfluid 4He using a vibrating wire

“…The critical velocity caused by the oscillators is much smaller than the intrinsic creation velocity of a vortex, which is about 60 m/s [8]. So the turbulence should be generated by the motion of remnant vortices on the wire.…”

Vortex nucleation in phase-slippage experiments in ultrapure superfluid4Hebelow 0.5 K

“…The crossover temperature reported by Hendry et al, 47 at which the nucleation rate saturates in ion propagation experiments, a rather different instance of vortex nucleation, lies at around 200 to 240 mK. In terms of the corresponding attempt frequencies, these different figures lie at in the same range.…”

“…21 Hosts of other mesoscopic systems are thought to exhibit quantum-tunneling phenomena, for instance, charge-density waves in quasi-one-dimensional conductors, 34,35 vortices in superconductors, 36,37 vortices and spin domains in BoseEinstein condensates, 38,39 cavitation of bubbles in helium, [40][41][42] crystalization in 4 He, 43 magnetic clusters. 44,45 They are also believed to occur in the nucleation of superfluid vortices, both in ion propagation 46,47 and in orifice flow, 10,13,16 -18,48,49 as well as for vortices in cosmology. 50 In all these last instances, the evidence stemming from experiments is less convincing and the applicability of theory conveys less confidence than that for the Josephson devices.…”

Untitled

“…A considerable amount is known about the properties [12][13][14][15] of vortices, and about how they are created at very low temperatures [16][17][18] but the mechanism responsible for the vorticity that appears 19,8 as a result of passing through the λ-transition (which separates the normal helium-I and the superfluid helium-II phases) is not understood. One possibility is that preexisting rotational flow caused by e.g.…”