Abstract
This paper presents a conserving approximation for a single magnetic impurity embedded in a BCS superconductor according to the Anderson model. The calculation generalizes the second-order selfenergy theory of a normal metal host into a superconducting medium. Within the second-order theory, both spin and pairing fluctuations contribute to the selfenergy. The second-order theory removes the unphysical spontaneous symmetry breaking of the Hartree-Fock approximation but results in a doubling of the bound-state spectrum within the energy gap. The HF bound states may be recovered in the small-U limit as the average of the two separate bound states. For increasing U, the novel pronounced low-energy bound states tend towards the center of the gap while the other bound states approach the gap edge and their spectral weights vanish.
Original language | English |
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Pages (from-to) | 193-203 |
Number of pages | 11 |
Journal | Journal of Magnetism and Magnetic Materials |
Volume | 438 |
DOIs | |
Publication status | Published - 15 Sept 2017 |
MoE publication type | A1 Journal article-refereed |