Effects of Impurities with Singlet--Triplet Configuration on Multiband Superconductors

概要

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Roles of multipole degrees of freedom in multiband superconductors are investigated in a case of impurities whose low-lying states consist of singlet ground and triplet excited states, which is related to the experimental fact that the transition temperature T_{\text{c}} is increased by Pr substitution for La in LaOs4Sb12. The most important contribution to the T_{\text{c}} increase comes from the inelastic interband scattering of electrons coupled to quadrupole or octupole moments of impurities. It is found that a magnetic field modifies an effective pairing interaction and the scattering anisotropy appears in the field-orientation dependence of the upper critical field H_{\text{c2}} in the vicinity of T_{\text{c}}, although a uniaxial anisotropic field is required for experimental detection. This would be proof that the Pr internal degrees of freedom are relevant to the stability of superconductivity in (La1-xPrx)Os4Sb12.
2011-06-15