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

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.

10 pages, 3 figures

References in corpus (2)

• Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials
• A Review of the Properties of Nb3Sn and Their Variation with A15 Composition, Morphology and Strain State

Cited by in corpus (4)

• Anharmonic theory of superconductivity in the high-pressure materials
• Superconducting dome in ferroelectric-type materials from soft mode instability
• Superconducting properties variation with A15 composition in Nb3Sn
• Impact of strain and field ramp functional form on thermomagnetic instabilities in composite Nb3Sn wires with multi-filaments inside the superconducting coil