Ground State Properties and Localized Excited States around a Magnetic Impurity Described by the Anisotropic s-d Interaction in Superconductivity

We investigate the electronic state around a magnetic impurity in the superconductivity in order to clarify how the anisotropy of the s-d interaction works in the presence of the superconducting energy gap. Using the numerical renormalization group method, we obtain regions induced by the anisotropy where two localized excited states with different energies appear at the same time; they cannot obtain as far as the isotropic interaction is considered. This means that the anisotropy of the s-d interaction works relevantly in some cases in the superconducting state. We also examine whether or not the bound state energy for the anisotropic and antiferromagnetic s-d interaction is scaled by T_K/Δ (T_K: Kondo temperature. Δ: superconducting order parameter), and find that it does not hold in the regions with two bound states.