# Regensburg 2010 – wissenschaftliches Programm

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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 Morawetz^{1,2}, Pavel Lipavský^{3,4}, Bretislav Šopík^{4}, and Michael Männel^{5} — ^{1}University of Applied Science Münster, Stegerwaldstrasse 39, 48565 Steinfurt, Germany — ^{2}International Center for Condensed Matter Physics, Universidade de Brasília, 70904-910, Brasília-DF, Brazil — ^{3}Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, 12116 Prague 2, Czech Republic — ^{4}Institute of Physics, Academy of Sciences, Cukrovarnická 10, 16253 Prague 6, Czech Republic — ^{5}Institute 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.