Unpaired Electrons in the Heavy-Fermion Superconductor CeCoIn_{5}

TL;DR

This study investigates the effects of impurities on the superconducting properties of CeCoIn_{5}, revealing coexistence of uncondensed electrons and nodal quasiparticles, and proposing a multiband superconductivity model.

Contribution

It provides new insights into the multiband nature of superconductivity in CeCoIn_{5} and the coexistence of uncondensed electrons with nodal quasiparticles.

Findings

Residual electronic specific heat increases with impurity concentration.

Residual electronic thermal conductivity decreases with impurity concentration.

Evidence supports a multiband superconductivity scenario with different gap structures.

Abstract

Thermal conductivity and specific heat were measured in the superconducting state of the heavy fermion material Ce_{1-x}La_{x}CoIn_{5}. With increasing impurity concentration x, the suppression of T_{c} is accompanied by the increase in the residual electronic specific heat expected of a d-wave superconductor, but it occurs in parallel with a decrease in residual electronic thermal conductivity. This contrasting behavior reveals the presence of uncondensed electrons coexisting with nodal quasiparticles. An extreme multiband scenario is proposed, with a d-wave superconducting gap on the heavy-electron sheets of the Fermi surface and a negligible gap on the light, three-dimensional pockets.