Quasiparticle excitations and dynamic susceptibilities in the BCS-BEC crossoverJ. Bauer1 and A. C. Hewson2
1 Max-Planck Institute for Solid State Research - Heisenbergstr.1, 70569 Stuttgart, Germany, EU
2 Department of Mathematics, Imperial College London - London SW7 2AZ, UK, EU
received 12 November 2008; accepted in final form 12 December 2008; published January 2009
published online 20 January 2009
We study dynamic ground-state properties in the crossover from weak-(BCS) to strong-coupling (BEC) superfluidity. Our approach is based on the attractive Hubbard model which is analyzed by the dynamical mean-field theory (DMFT) combined with the numerical renormalization group (NRG). We present an extension of the NRG method for effective impurity models to self-consistent calculations with superconducting symmetry breaking. In the one-particle spectra we show quantitatively how the Bogoliubov quasiparticles at weak coupling become suppressed at intermediate coupling. We also present results for the spin and charge gap. The extension of the NRG method to self-consistent superconducting solutions opens the possibility to study a range of other important applications.
71.10.Fd - Lattice fermion models (Hubbard model, etc.).
73.22.Gk - Broken symmetry phases.
74.20.Fg - BCS theory and its development.
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