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TT: Fachverband Tiefe Temperaturen
TT 24: SC: Properties, Electronic Structure, Mechanisms
TT 24.16: Vortrag
Mittwoch, 24. März 2010, 18:30–18:45, H19
Conserving T-matrix theory of superconductivity — •Klaus Morawetz1,2, Pavel Lipavský3,4, Bretislav Šopík4, and Michael Männel5 — 1University of Applied Science Münster, Stegerwaldstrasse 39, 48565 Steinfurt, Germany — 2International Center for Condensed Matter Physics, Universidade de Brasília, 70904-910, Brasília-DF, Brazil — 3Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, 12116 Prague 2, Czech Republic — 4Institute of Physics, Academy of Sciences, Cukrovarnická 10, 16253 Prague 6, Czech Republic — 5Institute of Physics, Chemnitz University of Technology, 09107 Chemnitz, Germany
Any many-body approximation corrected for unphysical repeated collisions in a given condensation channel is shown to provide the same set of equations as they appear by using anomalous propagators. The ad-hoc assumption in the latter theory about non-conservation of particle numbers can be released. In this way the widespread used anomalous propagator approach is given another physical interpretation. A generalized Soven equation follows which improves any approximation in the same way as the coherent potential approximation (CPA) improves the averaged T-matrix for impurity scattering. A selfconsistent T-matrix theory of many-Fermion systems is proposed. In the normal state the theory agrees with the Galitskii-Feynmann approximation, in the superconducting state it has the form of the renormalized Kadanoff-Martin approximation. The two-particle propagator satisfies the Baym-Kadanoff symmetry condition which guarantees that the theory conserves the number of particles, momentum and energy.