Criterion for Weak Spin–Orbit Coupling in Heavy-Fermion Superconductivity: Numerical Renormalization-Group Study

Abstract

A criterion for effective irrelevancy of the spin–orbit coupling in heavy-fermion superconductivity is discussed on the basis of the impurity Anderson model with two sets of Kramers doublets. Using Wilson’s numerical renormalization-group method, we demonstrate a formation of the quasi-particle as well as the renormalization of the rotational symmetry-breaking interaction in the lower Kramers doublet (quasi-spin) space. A comparison with the quasi-spin conserving interaction exhibits the effective irrelevancy of the rotational symmetry-breaking interaction for the splitting of two doublets Δ larger than the characteristic energy of the local spin fluctuation T_K. The relevance to lattice models is briefly discussed.