Dispersion relations for the BEC/BCS crossover

Ray Rivers

Imperial College London, UK

The talk will be based on paper above and subsequent work. We show how the properties of the BEC/BCS crossover in the presence of a Feshbach resonance at T=0 can be derived from the one-loop effective action. In particular, using a two-fluid description, we calculate the dispersion relations for both phonons and the Higgs mode throughout the BCS and BEC regimes and discuss the utility of the Gross-Pitaeveskii equations. composite two -fluid system.

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