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TT: Fachverband Tiefe Temperaturen

TT 7: SC: Properties, Electronic Structure, Mechanisms 2

TT 7.2: Talk

Monday, March 14, 2011, 14:15–14:30, HSZ 301

First principles study of the spin-orbit coupling effect on the Tl-Pb-Bi superconducting alloys — •Omar De la Peña-Seaman, Rolf Heid, and Klaus-Peter Bohnen — Karlsruher Institut für Technologie (KIT), Institut für Festkörperphysik, Germany

We have studied the influence of spin-orbit coupling (SOC) on the phonon properties, the electron-phonon (e-ph) coupling and on the superconducting properties for the Pb-Bi and Pb-Tl alloys in the stable fcc-phase doping regimes. These systems have been studied within the framework of density functional perturbation theory, using a mixed-basis pseudopotential method and the virtual crystal approximation (VCA) for modeling the alloys. The Eliashberg spectral function (α²F(ω)) and the electron-phonon coupling parameter (λ) have been calculated with and without SOC. The observed effects of SOC in the full phonon dispersion and α²F(ω) consist in a softening of the phonon frequencies and an increase of the e-ph coupling matrix elements, which become weaker on the Tl-rich side. SOC enhances λ by as much as 48% in some cases and improves its overall behavior as a function of the concentrations for the alloy systems, leading to a very nice agreement with experimental data from tunneling measurements.