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arXiv · 1401.2843

A theory of the strain-dependent critical field in Nb3Sn, based on anharmonic phonon generation

Davide Filippo Valentinis·Christophe Berthod·Bernardo Bordini·Lucio Rossi
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Abstract

We propose a theory to explain the strain dependence of the critical properties in A15 superconductors. Starting from the strong-coupling formula for the critical temperature, and assuming that the strain sensitivity stems mostly from the electron-phonon alpha^2F function, we link the strain dependence of the critical properties to a widening of alpha^2F. This widening is attributed to the nonlinear generation of phonons, which takes place in the anharmonic deformation potential induced by the strain. Based on the theory of sum- and difference-frequency wave generation in nonlinear media, we obtain an explicit connection between the widening of alpha^2F and the anharmonic energy. The resulting model is fit to experimental datasets for Nb3Sn, and the anharmonic energy extracted from the fits is compared with first-principles calculations.

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Davide Filippo Valentinis, Christophe Berthod, Bernardo Bordini, Lucio Rossi. 2014-01-13. A theory of the strain-dependent critical field in Nb3Sn, based on anharmonic phonon generation. https://doi.org/10.1088/0953-2048%2F27%2F2%2F025008

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