Impurity effect in a holographic superconductor

TL;DR

This paper investigates how homogeneous impurities affect a holographic superconductor by coupling a massive gauge field, revealing impurity-induced condensation, gap disappearance, and resonance features in optical conductivity.

Contribution

It introduces a novel coupling between the gauge field and a massive impurity field in a holographic superconductor model, analyzing impurity effects in the probe limit.

Findings

Impurity coupling induces condensation of the massive gauge field.

Large coupling eliminates the optical gap.

Resonance peak appears in the conductivity for the impurity field.

Abstract

We consider a holographic superconductor with homogeneous impurities added. We start with the holographic Abelian-Higgs model for s-wave superconductivity, and turn on a coupling between the gauge field and a new massive gauge field that is introduced for impurities, whose effect is examined in the probe limit. We find that the condensation of the massive gauge field is induced in the superconducting phase. When the coupling is sufficiently large, the mass gap in the optical conductivity disappears. A resonance peak is found in the conductivity for the massive vector field.