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Group expansions for impurities in superconductors

Yu. G. Pogorelov·V. M. Loktev
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Abstract

A new method is proposed for practical calculation of the effective interaction between impurity scatterers in superconductors, based on algebraic properties of related Nambu matrices for Green functions. In particular, we show that the density of states within the s-wave gap can have a non-zero contribution (impossible either in Born and in T-matrix approximation) from non-magnetic impurities with concentration $c \ll 1$, beginning from $\sim c^{3}$ order.

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Yu. G. Pogorelov, V. M. Loktev. 2003-11-17. Group expansions for impurities in superconductors. https://doi.org/10.1103/physrevb.69.214508

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