Magnetic impurity-induced states in the gap of an s± superconductor

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Abstract

We consider a two-band superconductor (SC) whose order parameter (OP) components in each band are constants of opposite sign. Conduction electrons interact with impurities described by the Anderson model. We calculate the density of states (DOS) of this system within a mean-field slave-boson approximation. The position of impurity-induced states in the energy gap depends strongly on the relative size of the energy of the impurity resonant level εf, its width Γ and the size of OP components Δ1, Δ2. In the Kondo limit the bound states are at the gap center or in its vicinity. In the mixed valence regime these bound states can be located far from the gap center. However they never reach the edge of the smaller of the two superconducting gaps. We also briefly discuss the consequences of varying the relative strengths of pairing and impurity coupling on low-energy properties of the system.

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