Scope for realizing the Josephson and proximity direct-current effects in helium II

Kiknadze, L.V.; Mamaladze, Yu.G.; Cheishvili, O.D.

doi:10.1007/bf00862125

Cited by 2 publications

(1 citation statement)

References 8 publications

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“…It is impossible to understand these effects if one thinks in terms of a mean field transition. This is the approach taken some time ago by Mamaladze and Cheishvili [38,39] in considering the possibility of what would constitute a weak link to couple two region of helium and display Josephson effects [40]. This mean field approach does not work for the effects discussed here as has been calculated explicitly [10].…”

Section: Dmentioning

confidence: 96%

Long-distance correlation-length effects and hydrodynamics ofHe4films in a Corbino geometry

2016

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Previous measurements of the superfluid density ρs and specific heat for 4 He have identified effects that are manifest at distances much larger than the correlation length ξ3D [1-3]. We report here new measurements of the superfluid density which are designed to explore this phenomenon further. We determine the superfluid fraction ρs/ρ from the resonance of 34 nm films of varying widths 4 ≤ W ≤ 100 µm. The films are formed across a Corbino ring separating two chambers where a thicker 268 nm film is formed. This arrangement is realized using lithography and direct Si-wafer bonding. We identify two effects in the behavior of ρs/ρ : one is hydrodynamic, for which we present an analysis; and the other, a correlation-length effect which manifests as a shift in the transition temperature Tc relative to that of a uniform 34 nm film uninfluenced by proximity effects. We find that one can collapse both ρs/ρ and the quality factor of the resonance onto universal curves by shifting Tc as ∆Tc ∼ W −ν. This new scaling is a surprising result on two counts: it involves a very large length scale W relative to the magnitude of ξ3D; and, the dependence on W is not what is expected from correlation-length finite-size scaling which would predict ∆Tc ∼ W −1/ν .

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Section: Dmentioning

confidence: 96%

Long-distance correlation-length effects and hydrodynamics ofHe4films in a Corbino geometry

2016

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Critical Point Coupling and Proximity Effects inHe4at the Superfluid Transition

Perron

Gasparini

2012

Phys. Rev. Lett.

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We report measurements of the superfluid fraction ρ(s)/ρ and specific heat c(p) near the superfluid transition of 4He when confined in an array of (2 μm)3 boxes at a separation of S=2 μm and coupled through a 32.5 nm film. We find that c(p) is strongly enhanced when compared with data where coupling is not present. An analysis of this excess signal shows that it is proportional to the finite-size correlation length in the boxes ξ(t,L), and it is measurable as far as S/ξ∼30-50. We obtain ξ(0,L) and the scaling function (within a constant) for ξ(t,L) in an L3 box geometry. Furthermore, we find that ρ(s)/ρ of the film persists a full decade closer to the bulk transition temperature T(λ) than a film uninfluenced by proximity effects. This excess in ρ(s)/ρ is measurable even when S/ξ>100, which cannot be understood on the basis of mean field theory.

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Scope for realizing the Josephson and proximity direct-current effects in helium II

Cited by 2 publications

References 8 publications

Long-distance correlation-length effects and hydrodynamics ofHe4films in a Corbino geometry

Long-distance correlation-length effects and hydrodynamics ofHe4films in a Corbino geometry

Critical Point Coupling and Proximity Effects inHe4at the Superfluid Transition

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