Spin and orbital effects of Cooper pairs coupled to a single magnetic impurity

Mikito Koga; Masashige Matsumoto

doi:10.1103/PhysRevB.65.094434

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Spin and orbital effects of Cooper pairs coupled to a single magnetic impurity

Mikito Koga, Masashige Matsumoto

DOI 10.1103/PhysRevB.65.094434 · Physical Review B

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Abstract

The Kondo effect strongly depends on spin and orbital degrees of freedom of unconventional superconductivity. We focus on the Kondo effect in uniformly gapped superconducting systems (the two-dimensional px+ipy-wave and dx2−y2+idxy-wave superconductors here) to compare the magnetic properties of the spin-triplet and spin-singlet Cooper pairs. The difference appears when both of the paired electrons couple to a local spin directly. For the px+ipy wave, the ground state is always a spin doublet for a Simp=1/2 local spin, and it is always a spin singlet for Simp=1. The latter is due to uniaxial spin anisotropy of the triplet Cooper pair. For the dx2−y2+idxy wave, the interchange of ground states occurs, which resembles a competition between the Kondo effect and the superconducting energy gap in s-wave superconductors. Thus the internal degrees of freedom of Cooper pairs give a variety to the Kondo effect.