%0 Journal Article
%T A theory of the strain-dependent critical field in Nb3Sn, based on anharmonic phonon generation
%A Davide Filippo Valentinis
%A Christophe Berthod
%A Bernardo Bordini
%A Lucio Rossi
%J Physics
%D 2014
%I arXiv
%R 10.1088/0953-2048/27/2/025008
%X 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.
%U http://arxiv.org/abs/1401.2843v1