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Extreme Electron-Phonon Coupling in Boron-based Layered Superconductors

J. M. An·S. Y. Savrasov·H. Rosner·W. E. Pickett
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Abstract

The phonon-mode decomposition of the electron-phonon coupling in the MgB2-like system Li_{1-x}BC is explored using first principles calculations. It is found that the high temperature superconductivity of such systems results from extremely strong coupling to only ~2% of the phonon modes. Novel characteristics of E_2g branches include (1) ``mode lambda'' values of 25 and greater compared to a mean of $\sim 0.4$ for other modes, (2) a precipitous Kohn anomaly, and (3) E_2g phonon linewidths within a factor of ~2 of the frequency itself, indicating impending breakdown of linear electron-phonon theory. This behavior in borne out by recent inelastic x-ray scattering studies of MgB2 by Shukla et al.

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J. M. An, S. Y. Savrasov, H. Rosner, W. E. Pickett. 2002-09-10. Extreme Electron-Phonon Coupling in Boron-based Layered Superconductors. https://doi.org/10.1103/physrevb.66.220502

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