Studies of the decay of persistent currents in unsaturated films of superfluid<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">He</mml:mi></mml:mrow><mml:mprescripts /><mml:mrow /><mml:mrow><mml:mn>4</mml:mn></mml:mrow><mml:mrow /><mml:mrow /></mml:mmultiscripts></mml:mrow></mml:math>

Ekholm, D. T.; Hallock, R. B.

doi:10.1103/physrevb.21.3902

Cited by 40 publications

(21 citation statements)

References 26 publications

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“…Various predictions coming from the Kosterlitz-Thouless theory 1 of such a transition have been verified via measurements of the superfluid density, 2,3 thermal transport, 4 " 7 and persistent currents. 8 The transition is in the same universality class as, for instance, 2D melting, the superconducting transition in thin films, and some transitions in liquid crystals. It is thus of considerable theoretical and experimental interest.…”

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confidence: 96%

Universality of the Kosterlitz-Thouless Transition inHe4Films as a Function of Thickness

Finotello

Gasparini

1985

Phys. Rev. Lett.

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We report new measurements of thermal transport in 4 He films near the superfluid transition. We have done this to check on the universality of this transition as a function of thickness or T c between 1.37 and 1.88 K. Results from this study show for the first time a thickness or T c dependence of the two characteristic parameters for the thermal conduction, the ratio of diffusion constant to vortex core radius, D/a 2 , and the nonuniversal constant b. We suggest that the increase of b with film thickness is related to the bulk correlation length. PACS numbers: 64.70.-p, 67.40.pm, 67.70. + nThe superfluid transition in 4 He films has been studied extensively as one of the realizations of a twodimensional (2D) x-y system. Various predictions coming from the Kosterlitz-Thouless theory 1 of such a transition have been verified via measurements of the superfluid density, 2,3 thermal transport, 4 " 7 and persistent currents. 8 The transition is in the same universality class as, for instance, 2D melting, the superconducting transition in thin films, and some transitions in liquid crystals. It is thus of considerable theoretical and experimental interest. There are still, however, several aspects of the superfluid transition which merit further attention. Among these is the question of how this transition is modified when one deals with helium films substantially thicker than a few monolayers. One expects that as long as one is in a temperature region where the 3D correlation length would tend to be larger than the film thickness, then the 2D behavior should be manifest. It is clear, however, that aspects of this behavior must be modified in thick films, if for no other reason but the fact that the critical behavior is relegated to a progressively smaller region in temperature as the film's T c approaches the bulk 7\. We report in this Letter a study of thermal transport to look at this behavior. Our work can be viewed from the perspective of finite-size scaling and dimensionality crossover 9 but, perhaps more importantly, it should be viewed as a universality study of the KosterlitzThouless transition. This is analogous to the study of the critical behavior at the 3D superfluid transition along the A line on the pressure or 3 He-concentration plane. 10

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confidence: 96%

Universality of the Kosterlitz-Thouless Transition inHe4Films as a Function of Thickness

Finotello

Gasparini

1985

Phys. Rev. Lett.

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“…Equation (12) allows the determination of s in a nonequilibrium flow situation, while Eq. (13) gives s also at equilibrium where v s = 0. Note, from Eqs.…”

Section: Modelmentioning

confidence: 99%

“…18 One may justify using this model to study the dissipation properties of two-dimensional superfluids by recalling that experiments on 4 He films 19 show that the transition to the superfluid phase is indeed in the KT universality class and that these films have finite critical velocity. 13,20 In addition, most explanations of dissipation in superfluid flow [21][22][23][24] are based on vortex formation which is certainly a defining property of the two-dimensional XY model. It is, therefore, reasonable to use this model to address the questions of superfluid stability and dissipation.…”

Section: Modelmentioning

confidence: 99%

Metastable states in the planar two-dimensionalXYmodel and dissipation in superfluid flow

Batrouni

2004

Phys. Rev. B

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We use the Metropolis algorithm to study the stability of superfluid flow in a model system, namely the two-dimensional planar XY model. Flow properties are examined by studying the behavior of the system in metastable "twisted" states. We demonstrate the stability of superfluidity in this model and we discuss the Meissner effect and velocity quantization. We also study the critical velocity and dissipation by vortex creation and rotational flow and their dependence on the geometry of the system. An expression for the average superfluid velocity as a function of time, v s ͑t͒, is obtained and compared with experimental results.where n ͑ s ͒ is the normal (super) fluid density. The superfluid component does not carry entropy and flows without dissipation. The total particle current is thenwhere v s ͑v n ͒ is the velocity of the superfluid (normal) component. To obtain the expression for v s , we write the superfluid wave function as ͑r͒ = e i͑r͒ 0 ͑r͒, ͑4͒where 0 ͑r͒ is real. Then, PHYSICAL

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“…These data are taken for Tmuch below T c . 9 It is found that the addition of 3 He greatly enhances the decay. This is consistent with a greater density of free vortices in addition to those induced by finite velocity or perhaps depinning or other effects.…”

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confidence: 98%

“…1 Measurements which yield the superfluid density-third sound, 2 " 5 quartz microbalance, 6 and torsional oscillator 3,7 -as well as experiments on thermal transport, 8 persistent currents, 9 and vortex diffusivity 10 have provided tests for the static and dynamic aspects of this theory. A first series of measurements on aspects of 2D to 3D crossover and the universal character of the transition as a function of film thickness have also been reported.…”

mentioning

confidence: 98%

Critical Behavior of the Thermal Conductance ofHe3-He
Finotello
¹
,
Yu
²
,
Gasparini
³

1986
Phys. Rev. Lett.
15
0
0
0
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We report measurements of the connective conductance of 3 He-4 He films near the superfluid transition. This thermal response is tested for the critical behavior observed in pure 4 He films. We find that this is preserved for mixtures. The parameters 6 and D/a 2 , however, show a strong renormalization, and an unusual 3 He dependence. The conductance at fixed T-T c decreases upon addition of 3 He implying a decrease of the 2D correlation length. We observe a decrease in the maximum value of conductance which we attribute to a residual free-vortex density, even for T< T c .The superfluid transition of 4 He films when physisorbed on a two-dimensional (2D) substrate can be described by the vortex-antivortex unbinding theory of Kosterlitz and Thouless. 1 Measurements which yield the superfluid density-third sound, 2 " 5 quartz microbalance, 6 and torsional oscillator 3,7 -as well as experiments on thermal transport, 8 persistent currents, 9 and vortex diffusivity 10 have provided tests for the static and dynamic aspects of this theory. A first series of measurements on aspects of 2D to 3D crossover and the universal character of the transition as a function of film thickness have also been reported. 11 There is, in addition, in the case of liquid helium, the possibility to study the universal character of the transition in the presence of 3 He. Mixture films are, of course, the 2D analog of 3D mixtures; but, in fact, they are substantially richer in possibilities because of the important roles of the liquid-solid and liquid-vapor interfaces, and the arrangement of the 3 He relative to and along these interfaces. As regards the critical behavior, mixture films have been studied near the superfluid transition in several realizations: a submonolayer of 4 He and 3 He 12 ; multilayer films of 4 He with a more substantial amount of 3 He, concentrations up to 50% 13 ' 14 ; and a near monolayer of 4 He with a large amount of 3 He. 7 All of these realizations are of interest because, among other effects, the boundary conditions on the superfluid are quite different. In the first case one is dealing with a monolayer mixture bounded by a solid substrate on one side and effectively vacuum on the other. In the second case, larger amounts of 3 He and 4 He, one is dealing with what one may call a "slab" of a 3D mixture with the twist that the concentration is not quite uniform because of the underlying van der Waals field. In the last case one has a submonolayer mixture "sandwiched" between the solid substrate and a 3D-like layer of 3 He. There are aspects of these realizations having to do with location of the 3 He and 4 He, and possible mass rearrangement as the temperature is changed. Many of these questions are still not settled, and the extent to which they affect the critical behavior at the superfluid transition is not clear.The existing measurements with mixtures-mostly of the superfluid density-yield a picture of the transition which is qualitatively very similar to that of pure 4 He. The transition has the universal jum...

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Studies of the decay of persistent currents in unsaturated films of superfluidHe4

Cited by 40 publications

References 26 publications

Universality of the Kosterlitz-Thouless Transition inHe4Films as a Function of Thickness

Universality of the Kosterlitz-Thouless Transition inHe4Films as a Function of Thickness

Metastable states in the planar two-dimensionalXYmodel and dissipation in superfluid flow

Critical Behavior of the Thermal Conductance ofHe3-He
Finotello
¹
,
Yu
²
,
Gasparini
³

1986
Phys. Rev. Lett.
15
0
0
0
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Studies of the decay of persistent currents in unsaturated films of superfluidHe4

Cited by 40 publications

References 26 publications

Universality of the Kosterlitz-Thouless Transition inHe4Films as a Function of Thickness

Universality of the Kosterlitz-Thouless Transition inHe4Films as a Function of Thickness

Metastable states in the planar two-dimensionalXYmodel and dissipation in superfluid flow

Critical Behavior of the Thermal Conductance ofHe3-HeFinotello1, Yu2, Gasparini3 1986Phys. Rev. Lett.15000View full textAdd to dashboardCite

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Critical Behavior of the Thermal Conductance ofHe3-He
Finotello
¹
,
Yu
²
,
Gasparini
³

1986
Phys. Rev. Lett.
15
0
0
0
View full text Add to dashboard Cite