Manifestation of impurity induced s_{+-} -> s_{++} transition: multiband model for dynamical response functions

TL;DR

This paper explores how disorder induces a transition from s_{+-} to s_{++} symmetry in multiband superconductors, affecting their dynamical response functions and enabling phase-insensitive experimental detection.

Contribution

It provides a theoretical analysis of disorder effects on the superconducting gap and response functions, highlighting the gapless regime near the transition.

Findings

Disorder causes a transition from s_{+-} to s_{++} symmetry.

Gapless regime appears near the transition point.

Anomalies in response functions can reveal order parameter symmetry.

Abstract

We investigate effects of disorder on the density of states, the single particle response function and optical conductivity in multiband superconductors with s_{+-} symmetry of the order parameter, where s_{+-} -> s_{++} transition may take place. In the vicinity of the transition the superconductive gapless regime is realized. It manifests itself in anomalies in the above mentioned properties. As a result, intrinsically phase-insensitive experimental methods like ARPES, tunneling and terahertz spectroscopy may be used for revealing of information about the underlying order parameter symmetry.