3He film flow on a round rim beaker

Steel, Stephen C.; Harrison, John P.; Zawadzki, P.; Sachrajda, A. S.

doi:10.1007/bf00754714

Cited by 20 publications

(17 citation statements)

References 35 publications

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“…At temperatures T ∼ 1 mK, where 3 He is superfluid, the scattering occurs only on aerogel strands and boundary conditions may be varied by a small amount of 4 He which covers the strands by a few atomic layers. In pure 3 He the strands are covered by ∼ 2 atomic layers of paramagnetic solid 3 He [2] and the scattering is diffusive but in presence of more than ≈ 2.5 layers of 4 He it is nearly specular at low pressures and becomes purely diffusive above ≈ 25 bar [3][4][5][6][7]. The 4 He coverage also removes the solid 3 He, and spin is conserved during the scattering.…”

mentioning

confidence: 99%

Effect of Magnetic Boundary Conditions on SuperfluidHe3in Nematic Aerogel

2018

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We report results of experiments with superfluid 3 He confined in aerogels with parallel strands which lead to anisotropic scattering of 3 He quasiparticles. We vary boundary conditions for the scattering by covering the strands by different numbers of atomic 4 He layers and observe that the superfluid phase diagram and the nature of superfluid phases strongly depend on the coverage. We assume that the main reason of these phenomena is a magnetic channel of the scattering which becomes important at low coverages. Our results show that the magnetic channel also may be important in other Fermi systems with the triplet pairing.Introduction.-In many Fermi systems, e.g. in liquid 3 He, in some cold atomic gases, and unconventional superconductors, a triplet Cooper pairing occurs that results in superfluid (superconducting) states. An ideal object to study an effect of impurities on such states is 3 He: it has a spherical Fermi surface, its superfluid phases (A, B and A 1 ) are well understood, and its superfluid coherence length can be varied by pressure in range of 20-80 nm [1]. Although superfluid 3 He is originally pure, a well defined system of impurities can be introduced by a high porosity aerogel. In such experiments silica aerogels are typically used. The main effect of the aerogel is to scatter 3 He quasiparticles. At temperatures T ∼ 1 mK, where 3 He is superfluid, the scattering occurs only on aerogel strands and boundary conditions may be varied by a small amount of 4 He which covers the strands by a few atomic layers. In pure 3 He the strands are covered by ∼ 2 atomic layers of paramagnetic solid 3 He [2] and the scattering is diffusive but in presence of more than ≈ 2.5 layers of 4 He it is nearly specular at low pressures and becomes purely diffusive above ≈ 25 bar [3][4][5][6][7]. The 4 He coverage also removes the solid 3 He, and spin is conserved during the scattering. In contrast, in pure 3 He spin is not conserved due to a fast exchange between atoms of liquid and solid 3 He that should result in an additional spin-exchange (magnetic) scattering channel. However, experiments with silica aerogels do not show a clear evidence of the magnetic channel. In particular, the observed A-like and B-like phases correspond to A and B phases of bulk 3 He, regardless of presence or absence of 4 He [8][9][10][11][12][13][14]. Moreover, the superfluid transition temperature of 3 He in aerogel (T ca ) is independent on the coverage at high pressures [8,12] but slightly higher in presence of the coverage at lower pressures [15,16] probably due to the change of the scattering specularity. In most of theoretical models of 3 He in aerogel the magnetic channel is neglected except only a few papers where it was shown that the magnetic scattering may affect A-A 1 transition in high magnetic fields [17][18][19] and a heat transport in the normal phase [20].Presumably, the magnetic scattering in 3 He in silica aerogels is masked due to their small global anisotropy.

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confidence: 99%

Effect of Magnetic Boundary Conditions on SuperfluidHe3in Nematic Aerogel

2018

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“…The superfluidity of the 3 He film has been demonstrated in a series of film flow experiments: the classic emptying beaker experiment [10]; a torsional oscillator measurement of the superfluid density [11]; the detection of third sound [12]; and electrostatically driven and detected film flow [13,14]. In these cases the surfaces are polished metal and not well characterised.…”

Section: Superfluid 3 He Filmmentioning

confidence: 99%

“…10 The suppression of the superfluid transition temperature as a function of effective confinement. Data from RHUL [6], Queens [10], Purdue [11], RIKEN [14]. Inset shows blow up of RHUL and RIKEN data.…”

Section: Superfluid 3 He Confined In a Nanoscale Geometry: Review Of mentioning

confidence: 99%

Study of Superfluid $$^3$$ 3 He Under Nanoscale Confinement

et al. 2014

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“…3 He quasiparticles at the boundary either with pure 3 He or with 4 He pre-plating [21][22][23][24]. For pure 3 He on very flat carbon (Grafoil) substrates the first monolayer has solid-like density and is a Curie-law paramagnet.…”

Section: Scattering Ofmentioning

confidence: 99%

“…Freeman and Richardson [22] and Steel et al [24] studied superfluidity in thin films of 3 He, on mylar and copper substrates respectively. Both groups found suppression of the transition temperature for pure 3 He; the suppression was consistent with zero order parameter at the interface, as expected for diffuse scattering of the 3 He quasiparticles.…”

Section: Scattering Ofmentioning

confidence: 99%

Giant thermomechanical effect in normal liquid ³He

Sawkey¹,

Deptuck²,

Greenwood³

et al. 1998

Can. J. Phys.

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Measurements are presented of the thermomechanical coefficient of normal liquid3 He confined in a porous plug pre-plated with four monolayers of 4 He. These nonmagnetic monolayers displace the magnetic solid-like 3 He monolayers that are adjacent to the pore surfaces when the plug is filled with pure 3 He. In the low temperature limit (T ≤ 10 mK) the coefficient can be described by ∆P/∆T ∼ s/6v where ∆P is the pressure difference across the plug generated by the temperature difference ∆T and s and v are the molar entropy and molar volume. This low temperature limit corresponds to the condition d ≪ ℓq where d is the pore diameter and ℓq is the bulk liquid 3 He quasiparticle mean free path; that is, the quasiparticles are predominantly boundary scattered in the pores. The measured coefficient is half that calculated by Edwards, Culman and He. When compared with this new experimental result for the 4 He-plated porous plug, the earlier result for pure liquid 3 He is strikingly larger (by up to 30× at 2 mK). This enhancement is reminiscent of the giant thermopowers measured in Kondo and other dilute magnetic alloys. It is speculated that the enhanced thermomechanical coefficient for pure liquid 3 He is due to magnetic scattering of the 3 He quasiparticles by the two magnetic solid-like 3 He monolayers adjacent to the pore surfaces.

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3He film flow on a round rim beaker

Cited by 20 publications

References 35 publications

Effect of Magnetic Boundary Conditions on SuperfluidHe3in Nematic Aerogel

Effect of Magnetic Boundary Conditions on SuperfluidHe3in Nematic Aerogel

Study of Superfluid $$^3$$ 3 He Under Nanoscale Confinement

Giant thermomechanical effect in normal liquid ³He

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3He film flow on a round rim beaker

Cited by 20 publications

References 35 publications

Effect of Magnetic Boundary Conditions on SuperfluidHe3in Nematic Aerogel

Effect of Magnetic Boundary Conditions on SuperfluidHe3in Nematic Aerogel

Study of Superfluid $$^3$$ 3 He Under Nanoscale Confinement

Giant thermomechanical effect in normal liquid 3He

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Giant thermomechanical effect in normal liquid ³He