Role of d-wave pairing in $A15$ superconductors

TL;DR

This paper proposes that a d-wave pairing state coexists with s-wave superconductivity in V$_3$Si, explaining various experimental observations such as vortex core shrinking and anisotropic critical fields.

Contribution

It introduces a microscopic model for d-wave pairing in A15 superconductors and links it to experimental phenomena previously unexplained.

Findings

D-wave order explains the vortex core shrinking at low magnetic fields.

D-wave pairing accounts for the large anisotropy in the upper critical field.

Raman spectroscopy observations are consistent with a competing d-wave state.

Abstract

We argue that the recent Raman spectroscopy observation of a sharp mode in s-wave superconducting V$_3$Si is due to a competing d-wave pairing state. We present microscopic arguments for the origin of this d-wave order. We further argue that the d-wave order explains the observed shrinking of the vortex core structure at anomalously low magnetic fields and the large anisotropy observed in the upper critical field.