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arXiv · 1106.5322

On the Question of Coincidence Between Energy Gaps and Kohn Anomalies

S. Johnston·A. P. Sorini·B. Moritz·T. P. Devereaux·D. J. Scalapino
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Abstract

Recently, neutron scattering spin echo measurements have provided high resolution data on the temperature dependence of the linewidth $\Gamma({\bf q},T)$ of acoustic phonons in conventional superconductors Pb and Nb. [P. Aynajian, et al, Science 319, 1509 (2008)]. At low temperatures the merging of the $2\Delta(T)$ structure in the linewidth with a peak associated with a low lying $\hbar\omega_{\bf q_{KA}}$ Kohn anomaly suggested a coincidence between $2\Delta(0)$ and $\hbar\omega_{\bf q_{KA}}$ 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 $2\Delta(0)/\hbar\omega_{\bf q_{KA}}$ must be to unity in order to be consistent with the neutron data.

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S. Johnston, A. P. Sorini, B. Moritz, T. P. Devereaux, D. J. Scalapino. 2011-06-27. On the Question of Coincidence Between Energy Gaps and Kohn Anomalies. https://doi.org/10.1103/physrevb.84.174523

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