Berlin 2008 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 23: Correlated Electrons: (General) Theory

TT 23.15: Talk

Wednesday, February 27, 2008, 18:00–18:15, H 0104

Absence of fermionic quasi-particles in the BEC regime of the attractive Fermi gas — •Nils Lerch, Lorenz Bartosch, and Peter Kopietz — Institut für Theoretische Physik, Universität Frankfurt, Max-von-Laue Straße 1, 60438 Frankfurt, Germany

We calculate the effect of order parameter fluctuations on the fermionic single-particle excitations of the attractive Fermi gas in the BEC regime where the binding energy of the s-wave bound state is the largest energy scale. We show that in dimensions D=3 the singular interaction between the fermions mediated by the gapless Bogoliubov-Anderson mode prohibits the existence of well-defined quasi-particles. We explicitly calculate the single-particle spectral function and show that in this case the quasi-particle residue and the density of states are logarithmically suppressed.