Nonmagnetic impurity resonance states as a test of superconducting pairing symmetry in CeCoIn$_{5}$

TL;DR

This paper theoretically investigates how nonmagnetic impurities affect the local density of states in CeCoIn$_{5}$, proposing that impurity resonance states can distinguish between different pairing symmetries in this heavy fermion superconductor.

Contribution

It demonstrates that impurity resonance states are sensitive to pairing symmetry, specifically distinguishing $d_{x^{2}-y^{2}}$ from $d_{xy}$, aiding in identifying the superconducting pairing mechanism.

Findings

Only $d_{x^{2}-y^{2}}$ pairing shows robust impurity resonance states.

Both pairing symmetries produce similar V-shaped gap features in density of states.

Impurity resonance peaks can be detected by scanning tunneling microscopy.

Abstract

We theoretically study the effect of a nonmagnetic impurity in heavy fermion superconductor CeCoIn$_{5}$ within a realistic band model and the T-matrix approximation approach. By considering two known possible pairing symmetry candidates $d_{x^{2}-y^{2}}$ and $d_{xy}$, we find that although both total density of states exhibit a similar V-shaped gaplike feature, only the $d_{x^{2}-y^{2}}$-wave pairing symmetry gives rise to robust intragap impurity resonance states reflected by the resonance peaks near the Fermi energy in the local density of states. These features can be readily probed by scanning tunneling microscopy experiments, and are proposed to shed light on the pairing symmetry and provide hints on the microscopic mechanism of unconventional superconductivity in the Ce-based heavy fermion superconductors.