Superconductivity from a non-Fermi liquid metal : Kondo fluctuation mechanism in the slave-fermion theory

TL;DR

This paper proposes a novel mechanism for superconductivity driven by Kondo fluctuations in a non-Fermi liquid metal, leading to multi-gap superconductivity near an antiferromagnetic quantum critical point, distinct from traditional spin-fluctuation models.

Contribution

It introduces a new hybridization-based mechanism involving charge and spin fluctuations within the slave-fermion framework, explaining multi-gap superconductivity beyond conventional theories.

Findings

Identification of two resonance modes in spin and charge fluctuations.

The ratio of superconducting gaps to transition temperature matches experimental data for CeCoIn5.

Superconductivity arises from Kondo fluctuation mechanisms, not just spin fluctuations.

Abstract

We find new mechanism of superconductivity beyond the spin-fluctuation theory, the standard model for unconventional superconductivity in the weak coupling approach, where Kondo fluctuations result in multi-gap superconductivity around an antiferromagnetic quantum critical point of the slave-fermion theory. Fingerprints of the hybridization mechanism are two kinds of resonance modes in not only spin but also charge fluctuations, originating from $d-wave$ pairing of conduction electrons and spinless holons, respectively, thus differentiated from the spin-fluctuation mechanism. We show that the ratio between each superconducting gap for conduction electrons $\Delta_{c}$ and holons $\Delta_{f}$ and the transition temperature $T_{c}$ is $2\Delta_{c} / T_{c} \sim 9$ and $2\Delta_{f} / T_{c} \sim \mathcal{O}(10^{-1})$, remarkably consistent with $CeCoIn_{5}$.