Unconventional Superconductivity arising from Multipolar Kondo Interactions

TL;DR

This paper explores how multipolar Kondo interactions in cubic heavy fermion compounds can lead to unconventional superconductivity with diverse pairing symmetries and complex quasiparticle spectra.

Contribution

It introduces a theoretical framework linking multipolar fluctuations to superconducting instabilities, revealing novel pairing states with higher angular momentum and mixed parity.

Findings

Multiple superconducting states with different angular momenta ($J=0,1,2,3$) identified.

Both odd and even parity pairing functions are possible, independent of total angular momentum.

Coexistence of various pairing symmetries with gapped and nodal quasiparticle spectra.

Abstract

The nature of unconventional superconductivity is intimately linked to the microscopic nature of the pairing interactions. In this work, motivated by cubic heavy fermion compounds with embedded multipolar moments, we theoretically investigate superconducting instabilities instigated by multipolar Kondo interactions. Employing multipolar fluctuations (mediated by RKKY interaction) coupled to conduction electrons via two-channel Kondo and novel multipolar Kondo interactions, we uncover a variety of superconducting states characterized by higher-angular momentum Cooper pairs, $J=0,1,2,3$. We demonstrate that both odd and even parity pairing functions are possible, regardless of the total angular momentum of the Cooper pairs, which can be traced back to the atypical nature of the multipolar Kondo interaction that intertwines conduction electron spin and orbital degrees of freedom. We determine that different (point-group) irrep classified pairing functions may coexist with each other, with some of them characterized by gapped and point node structures in their corresponding quasiparticle spectra. This work lays the foundation for discovery and classification of superconducting states in rare-earth metallic compounds with multipolar local moments.