Hunds Rule Theory for Heavy Fermion Superconductors

TL;DR

This paper extends spin fluctuation theory to include orbital degeneracy effects in f electrons, predicting Hunds rule-based superconducting pair states consistent with experimental data in heavy fermion superconductors.

Contribution

It introduces a generalized theory incorporating orbital degeneracy, leading to predictions of Hunds rule-based superconducting states in heavy fermion materials.

Findings

Predicts a superconducting pair state obeying Hunds rules with specific quantum numbers.

Shows degeneracy breaking due to crystalline effects in UPt3.

Aligns theoretical predictions with experimental constraints.

Abstract

In this paper, a generalization of standard spin fluctuation theory is considered which takes into account orbital degeneracy effects which are critical for describing f electrons. This theory leads to an instability for a superconducting pair state which obeys Hunds rules. Such a state has L=5, S=1, and J=4. The degeneracy of this state is broken by crystalline effects, and realistic calculations for $UPt_3$ find a resultant pair state with $\Gamma_6^-$ symmetry, consistent with current experimental constraints.