Wilson ratio in Yb-substituted CeCoIn5

TL;DR

This study examines how Yb substitution affects the superconducting properties of CeCoIn$_5$, revealing that the Wilson ratio can be determined from key thermodynamic parameters and remains unaffected by disorder.

Contribution

We introduce a method to determine the Wilson ratio in Pauli limited superconductors using thermodynamic measurements, applicable in the clean limit.

Findings

Yb acts as a non-magnetic hole dopant in CeCoIn$_5$.

The upper critical field remains Pauli limited despite Yb doping.

The Wilson ratio is unaffected by disorder in the studied system.

Abstract

We have investigated the effect of Yb substitution on the Pauli limited, heavy fermion superconductor, CeCoIn$_5$. Yb acts as a non-magnetic divalent substituent for Ce throughout the entire doping range, equivalent to hole doping on the rare earth site. We found that the upper critical field in (Ce,Yb)CoIn$_5$ is Pauli limited, yet the reduced (H,T) phase diagram is insensitive to disorder, as expected in the purely orbitally limited case. We use the Pauli limiting field, the superconducting condensation energy and the electronic specific heat coefficient to determine the Wilson ratio ($R_{W}$), the ratio of the specific heat coefficient to the Pauli susceptibility in CeCoIn$_5$. The method is applicable to any Pauli limited superconductor in the clean limit.