Texture and hydrodynamics of a thin slab of superfluid3He-A in a torsional oscillator. II. Experiment

Hook, J. R.; Faraj, E.; Gould, S. G.; Hall, H. E.

doi:10.1007/bf00681752

Cited by 73 publications

(16 citation statements)

References 25 publications

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“…The results for ␤ 245 agree well with those from other experiments. 4,10,11 On the other hand, the present values ␤ 24 are in agreement with those reported by Tang et al 11 from the A-B transition measurement, but inconsistent with those of Bastea et al 12 In our analysis mentioned above, we have neglected strong-coupling corrections to the gradient term of the free energy, because they cannot be reliably extracted from experiments. Eqs.…”

Section: B Gl Coefficientscontrasting

confidence: 47%

“…Such a transition was also observed in a torsional oscillator experiment for the A phase by Berthord et al 3 and then investigated extensively by Hook et al 4 They reported a change of the normal fluid fraction due to the texture transition caused by the applied magnetic field and the liquid flow. In these phases with anisotropic energy gap, the texture plays an important role.…”

Section: Introductionsupporting

confidence: 52%

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Normal fluid fraction of superfluidA13in a high magnetic field

1997

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The normal fluid fraction nЌ / of superfluid 3 He-A 1 has been measured up to 12 T between 0 bar and 29 bars by use of a torsional oscillator. After taking into account a Fermi-liquid correction, the bare normal fluid fraction in the A 1 phase gives a combination of the Ginzburg-Landau coefficients ␤ 24 . At low pressures the value approaches the weak-coupling limit, and a strong-coupling correction increases with pressure. The results agree with thermodynamic measurements on the A-B phase transition in a magnetic field, but are inconsistent with recent spin-entropy-wave measurements.

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Section: B Gl Coefficientscontrasting

confidence: 47%

Section: Introductionsupporting

confidence: 52%

Normal fluid fraction of superfluidA13in a high magnetic field

1997

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“…Experimental information on the generalized Ginzburg-Landau fourth-order free energy coefficients pl, pz, ps, p4, and p5 suggests that the axiplanar state [4] might be more stable than the axial state over at least part of the A-phase region of the phase diagram. In addition, our own measurements of the A-phase superfluid density anisotropy at 29.3 bars [5] give a value for (p,~-ps~~) /p,~o f 0.42 +0.03 as T~T~, this represents a possibly significant departure from the value of 0.5 predicted for the axial state in the direction expected for an axiplanar order parameter. At the melting pressure strong coupling corrections [6] make the predicted anisotropy for the axial state slightly larger, 0.515.…”

Section: Identi6cation Of the Order Parameter Of She-amentioning

confidence: 70%

“…In addition, our own measurements of the A-phase superfluid density anisotropy at 29.3 bars [5] give a value for (p,~-ps~~) /p,~o f 0.42 +0.03 as T~T~, this represents a possibly significant departure from the value of 0.5 predicted for the axial state in the direction expected for an axiplanar order parameter. At the melting pressure strong coupling corrections [6] make the predicted anisotropy for the axial state slightly larger, 0.515.…”

mentioning

confidence: 70%

Identification of the order parameter ofA3using low-field NMR measurements

et al. 1994

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We have made simultaneous measurements of the longitudinal and transverse NMR frequencies of He-A in fields of the order of 30 G in a parallel plate geometry, defined by Mylar films 100pm apart, so that 1 is well oriented perpendicular to the static magnetic field. Comparison of our measurements with the quadratic axial-state frequency relation indicates that the A phase is axial in the pressure range 22.6 to 29.3bars. PACS numbers: 67.57.Lm, 76.60.Jx It has recently been suggested [1,2] that the conventional identification of the Cooper pair state in the A phase of superfluid 3He with the Anderson-Brinkman-Morel [3] (or axial) state might be incorrect. Experimental information on the generalized Ginzburg-Landaufourth-order free energy coefficients pl, pz, ps, p4, and p5 suggests that the axiplanar state [4] might be more stable than the axial state over at least part of the A-phase region of the phase diagram. In addition, our own measurements of the A-phase superfluid density anisotropy at 29.3 bars [5] give a value for (p,~-ps~~) /p,~o f 0.42 +0.03 as T~T~, this represents a possibly significant departure from the value of 0.5 predicted for the axial state in the direction expected for an axiplanar order parameter. At the melting pressure strong coupling corrections [6] make the predicted anisotropy for the axial state slightly larger, 0.515.Since the identification of the A phase with the axial state is the basis for much theoretical work and also for the interpretation of a substantial number of experiments, it is important that its validity should be thoroughly checked and that was the purpose of the work described in this Letter. The relationship between the longitudinal and transverse NMR frequencies, O~~a nd Ag, of the A phase provides a precise method for doing this. For t;he axial state in an applied magnetic Beld there is a simple quadratic relation between these frequencies ll 2 2 w here AL, is the Larmor frequency of the He nucleus. For the axiplanar state O~e xceeds 0& -0& by an amount which measures the cleparture of the order parameter from the axial form. Previously, Eq.(1) has been checked carefully only at the melting pressure 34.3 bars, [7] where the identification of the A phase with the axial state seems secure. The axiplanar order parameter is specified by angles 8 and P and it can conveniently be written in terms of the spin-space unit vector triad (d, e, f) and orbit-space unit vector triad (1, m, fl) [8] as proportional to We see that spin-up and spin-down states have diferent orbital anisotropy axes at angles +P to 1; the axial phase corresponds to the limit P~0 , 8~z/4. For P g 0 and 8 P z/4 expression (2) indicates a state with a coherent sum of orbital angular momentum up and down for each spin state.The axiplanar state is more stable than the axial state if p45 = p4 + ps ) 0, in which case the angles p and 8 are given in terms of the P's by [4] tan 2P13P45 P345(2PI + Ps)' cos 8= P3(2Pl + P345) 2[Ps(2P1 + P345) + P45(2P1 + P3)](3) We note that in the limit T~Tc the order parameter(2...

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“…We do not have any explanation for this observation. Although the parasitic resonances were absent we were still unable to determine the superfluid density within the aerogel because the addition of the 4 He also introduced a large thermal boundary resistance between the LCMN and the 3 He which preventing us from measuring the temperature.…”

Section: Measurements For 1% Aerogelmentioning

confidence: 99%

Torsional oscillator studies of the superfluidity of 3He in aerogel

Alles

Kaplinsky

Wootton

et al. 1998

Physica B: Condensed Matter

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We have made simultaneous torsional oscillator and transverse NMR measurements (at ∼ 165 kHz) on 3 He contained within aerogels with nominal densities of 1% and 2% of solid glass. The superfluid transition is seen simultaneously by both techniques and occurs at a temperature which agrees semi-quantitatively with that expected for homogeneous isotropic pair-breaking scattering of 3 He atoms by strands of silica. Values obtained for the superfluid density ρ s in the 2% sample are in reasonable agreement with those observed previously. Coupling of the torsional mode to a parasitic resonance prevented accurate determination of ρ s for the 1% aerogel. We have identified other resonances coupling to the torsional oscillations as sound modes within the helium/aerogel medium.

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Texture and hydrodynamics of a thin slab of superfluid3He-A in a torsional oscillator. II. Experiment

Cited by 73 publications

References 25 publications

Normal fluid fraction of superfluidA13in a high magnetic field

Normal fluid fraction of superfluidA13in a high magnetic field

Identification of the order parameter ofA3using low-field NMR measurements

Torsional oscillator studies of the superfluidity of 3He in aerogel

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