Polarization of the spin-density waves in lead

Overhauser, A. W.; Tm, Giebultowicz

doi:10.1103/physrevb.47.14338

Cited by 13 publications

(6 citation statements)

References 27 publications

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“…The Chen-Overhauser matrix depends on a parameter, A, adjustable for data fitting [22]. Unfortunately an experiment in 1992 by Overhauser and Giebuttowicz was unable to demonstrate that spin-density waves were relevant to explaining lead phonon dispersion [23].…”

Section: Lead: Lattice Dispersionmentioning

confidence: 99%

BCS theory has to be overhauled: Reassurance from numerical survival rate

Zheng¹,

Walmsley²

2016

Solid State Communications

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The BCS theory has conceptual and numerical difficulties. We have previously overhauled it with a new scheme of phonon-mediated electron pairing that can be expressed analytically in terms of an empirical pairing survival rate factor, S(q) = 0 or 1/2, depending on phonon momentum, q. Now we evaluate S(q) numerically entirely from experimental data on normal state electrical resistivity and on superconducting tunnelling conductance. The empirical and numerical S(q) are reassuringly close in aluminium and lead and particularly so in two other cases, niobium and tantalum.

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Section: Lead: Lattice Dispersionmentioning

confidence: 99%

BCS theory has to be overhauled: Reassurance from numerical survival rate

Zheng¹,

Walmsley²

2016

Solid State Communications

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“…7 ͑referred to as Paper I͒, we discuss these and other experiments cited as evidence for SDWs in Pb. 8 Our experiments use high frequency ballistic phonons as an internal probe of superconducting Pb. Phonons with energies below the superconducting gap energy can travel ballistically across millimeter-sized crystals of pure Pb, occasionally scattering from thermally excited quasiparticles.…”

mentioning

confidence: 99%

Influence of nonequilibrium quasiparticles in phonon imaging of superconductors: Consistency with BCS theory in Pb crystals

Head

Wolfe

2008

Phys. Rev. B

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This paper is the second part of a study motivated by the prediction of Overhauser and Daemen ͓A. W. Overhauser and L. L. Daemen, Phys. Rev. Lett. 61, 1885 ͑1988͔͒ that the electronic ground state of Pb exhibits a spin-density wave ͑SDW͒ that leads to a highly anisotropic superconducting gap. The first part of our study ͓J. D. Short, T. L. Head, and J. P. Wolfe, Phys. Rev. B 78, 054515 ͑2008͔͒ extended the theoretical predictions to the actual Fermi surface of Pb and initiated phonon imaging experiments on high purity Pb. The temperature dependence of the phonon absorption by quasiparticles over a 1.45-2.1 K temperature range was found to be much weaker than the exp͑−⌬ o / k B T͒ form using the generally accepted gap parameter ⌬ o = 1.35 meV for Pb. In addition, the absorption coefficients obtained for two crystals of different thickness were not consistent with phonon absorption by quasiparticles in thermal equilibrium with the lattice. To explain these two anomalies in the context of the BCS theory of superconductivity, we examine the possible effects of nonequilibrium quasiparticles generated by the laser source and bolometer detector. Detailed experiments varying crystal length, source size, excitation power, and pulse duration over wide limits enable us to isolate the phonon absorption by both nonequilibrium and thermal-equilibrium quasiparticles. The wide variety of data yields an equilibrium quasiparticle density that varies as exp͑−⌬ / k B T͒ with ⌬ = 1.32Ϯ 0.07 meV, in good agreement with BCS theory with ⌬ o = 1.35 meV, and inconsistent with the electronic-specific-heat data of van der Hoeven and Keesom ͓B. J. C. van der Hoeven, Jr. and P. Keesom, Phys. Rev. 137, 103 ͑1965͔͒ that motivated the SDW hypothesis in Pb. In summary, the highly anisotropic absorption of ballistic phonons in superconducting Pb provides a unique measure of equilibrium quasiparticle density that agrees with BCS theory extending to exp͑−⌬ / k B T͒ = 2.6ϫ 10 −5 at 1.45 K.

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“…However the SDW polarization vectorê would have to be transverse. Longitudinally polarized SDW's in (nearly free-electron) metals are invisible to neutrons, as has been found in Pb [6]. (ii) The SDW may cause a local dip in the longitudinal phonon mode near ͑0, 0, 1 2 ͒ [7].…”

mentioning

confidence: 99%

Polarization of the spin-density waves in lead

Cited by 13 publications

References 27 publications

BCS theory has to be overhauled: Reassurance from numerical survival rate

BCS theory has to be overhauled: Reassurance from numerical survival rate

Influence of nonequilibrium quasiparticles in phonon imaging of superconductors: Consistency with BCS theory in Pb crystals

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