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.
Highlights
In the single-impurity limit, so-called multipolar Kondo interactions lead to the development of both multi-channel as well as exotic non-Fermi liquid states, where both the conduction electron spin and orbital degrees of freedom become intertwined under scattering events with the moment [42,43,44,45]
In this work, motivated by superconducting behaviours in ferro-quadrupolar PrTi2Al20 [64], we investigate the superconducting instability instigated by multipolar Kondo interactions
The cubic nature of the interactions necessitates that the Cooper pair operators of total angular momentum bJ†,M;k be organized into the irreducible representations of the associated point-group Oh, rather than the good quantum number of spherical symmetry, J [70,71,72]
Summary
The instability of the Fermi liquid state to interactions is at the heart of a wealth of emergent phenomena. In the single-impurity limit, so-called multipolar Kondo interactions lead to the development of both multi-channel as well as exotic non-Fermi liquid states, where both the conduction electron spin and orbital degrees of freedom become intertwined under scattering events with the moment [42,43,44,45]. Employing a Ginzburg-Landau theory of ferro-multipolar ordering (mediated by RKKY interaction), we consider Gaussian multipolar fluctuations in the high-symmetry paramagnetic phase These fluctuations (and the associated order parameters) are symmetry-permitting and coupled to conduction electrons possessing spin (↑, ↓) and orbital ( = 1) degrees of freedom.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
