Differential Conductance and Defect States in the Heavy Fermion Superconductor CeCoIn$_5$

TL;DR

This study combines experimental spectroscopy and theoretical modeling to analyze the electronic structure and defect states in the heavy fermion superconductor CeCoIn$_5$, revealing multiple $d_{x^2-y^2}$-symmetry gaps.

Contribution

It demonstrates how the bandstructure and superconducting gap models can explain the observed conductance lineshape and impurity states in CeCoIn$_5$, supporting a microscopic theory of its unconventional superconductivity.

Findings

The $dI/dV$ lineshape reflects multiple $d_{x^2-y^2}$-symmetry gaps.

Impurity states show spatial structures consistent with the superconducting gap symmetry.

Results support a microscopic origin of the unconventional superconducting state.

Abstract

We demonstrate that the electronic bandstructure extracted from quasi-particle interference spectroscopy [Nat. Phys. 9, 468 (2013)] and the theoretically computed form of the superconducting gaps [Proc. Nat. Acad. Sci. 111, 11663 (2014)] can be used to understand the $dI/dV$ lineshape measured in the normal and superconducting state of CeCoIn$_5$ [Nat. Phys. 9, 474 92103)]. In particular, the $dI/dV$ lineshape, and the spatial structure of defect-induced impurity states, reflects the existence of multiple superconducting gaps of $d_{x^2-y^2}$-symmetry. These results strongly support a recently proposed microscopic origin of the unconventional superconducting state.