Multiband Superconductivity: Anisotropy, Scattering and Bound States

First principles modeling of phonon mediated s-wave superconductors has been largely successful for bulk crystals [1], however, the incorporation of impurities in such theories will be much harder. This problem becomes particularly relevant as impurities affect the superconducting state and magnetic impurities are pair breaking and lead to bound states [2]. Such states are a possible source of Majorana Fermions [3]. Here we present the implementation of the Bogoliubov-de Gennes (BdG) equation into a Green’s function (KKR) first principles method [4]. This method is ideal to model impurities and interfaces without the need of artificial supercells. We parameterize the pairing potential but solve the BdG equation self-consistently incorporating microscopic electronic properties of real materials. Our method allows us to investigate the rich complexity of gap anisotropy on the Fermi surface and also how real magnetic and non-magnetic impurities interfere with the superconducting state.

[1] F. Giustino, Rev. Mod. Phys., 89, 019901 (2019)
[2] B. W. Heinrich et al, Prog. Surf. Sci., 93, 1 (2018)
[3] S. Nadj-Perge et al, Science, 346, 1259327 (2014)
[4] G. Csire et al, Phys. Rev. B, 91, 165142 (2015)