"Coincidence between energy gaps and Kohn anomalies in conventional superconductors"

S. Johnston: A. P. Sorini, B. Moritz, T. P. Devereaux, and D. J. Scalapino; Phys. Rev. B, 11/23/11.

Additional Authors: A. P. Sorini, B. Moritz, T. P. Devereaux, and D. J. Scalapino

Abstract:

Recently, neutron scattering spin-echo measurements have provided high-resolution data on the temperature dependence of the linewidth Γ(q,T) of acoustic phonons in conventional superconductors Pb and Nb [ P. Aynajian et al. Science 319 1509 (2008)]. At low temperatures, the merging of the 2Δ(T) structure in the linewidth with a peak associated with a low-lying ℏωqKA Kohn anomaly suggested a coincidence between 2Δ(0) and ℏωqKA in Pb and Nb. Here we carry out a standard BCS calculation of the phonon linewidth to examine its temperature evolution and explore how close 2Δ(0)/ℏωqKA must be to unity in order to be consistent with the neutron data.