Dresden 2006 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 18: Superconductivity: Borides, Borocarbides, Carbides, ...
TT 18.3: Vortrag
Dienstag, 28. März 2006, 15:30–15:45, HSZ 02
Density functional theory for superconductors: Applications to MgB2 and Pb — •A. Floris1, N. Lathiotakis1, A. Sanna2, C. Franchini2, M. Marques3, M. Lueders4, G. Profeta5, A. Continenza5, S. Massidda2, and E.K.U. Gross1 — 1Freie Universitaet Berlin, Arnimallee 14, D-14195 Berlin, Germany — 2INFM SLACS and Dipartimento di Scienze Fisiche, Universita’ degli Studi di Cagliari, Italy — 3Institut de Minéralogie et de Physique des Milieux Condensés, Université Pierre et Marie Curie - Paris VI, France — 4Daresbury Laboratory, Warrington WA4 4AD, United Kingdom — 5C.A.S.T.I. - INFM and Dipartimento di Fisica, Universita’ degli studi dell’Aquila, Italy
Predicting the properties of superconductors is of both fundamental and technological importance. The discovery of superconductivity in MgB2 (Tc=39.5 K), with a clear presence of two gaps, has renewed the interest in conventional superconductivity. Here we present two applications of a novel approach to superconductivity that allows one to calculate material-specific properties without using any adjustable parameters. Within this approach, we have obtained the critical temperature and the two gaps of MgB2 in good agreement with experiment, taking into account the strong anisotropy of both the electron-phonon and the Coulomb interactions. Moreover, in a fully k-resolved formalism, we find two different gaps also in Pb, and we relate this fact to the difference in strength of the electron-phonon coupling associated with the two bands crossing the Fermi level. This calculation shows how our formalism is able to capture, in absence of any ad-hoc model, the features of multi-gap superconductors.