Neutron-scattering profile of Q≠0 phonons in BCS superconductors

Abstract

Phonons in a metal interact with conduction electrons. In the normal state, this gives rise to a linewidth γQ which is small compared with the frequency ωQ. In the superconducting state, the line shape can be altered if ħωQ≲(1+2r)2Δ where Δ is the superconducting gap, and r is the ratio γQ/ωQ, which scales with the strength of the electron-phonon coupling λ. As long as ωQ≪QvF where vF is the Fermi velocity, BCS theory predicts a line shape which is a universal function of the dimensionless parameters r, ωQ/2Δ, ω/2Δ, and T/Tc where Tc is the superconducting transition temperature. Formulas and curves are given for the full range of these parameters. The BCS predictions correspond well to key features seen in recent experiments on YNi2B2C and LuNi2B2C.

Source-reported materials — not catalogue approval

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