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TT: Fachverband Tiefe Temperaturen

TT 15: MLT: Quantum Liquids, Bose-Einstein Condensates, Ultra-cold Atoms, ... 1

TT 15.2: Vortrag

Dienstag, 23. März 2010, 14:15–14:30, H18

Ward identities and skeleton equations in the functional renormalization group approach to the BCS-BEC crossover — •Lorenz Bartosch¹, Peter Kopietz¹, and Alvaro Ferraz² — ¹Institut für Theoretische Physik, Universität Frankfurt, Germany — ²International Center for Condensed Matter Physics, Universidade de Brasília, Brazil

We use the functional renormalization group approach with partial bosonization in the particle-particle channel to study the effect of order parameter fluctuations on the BCS-BEC crossover of superfluid fermions in three dimensions. Our approach is based on a new truncation of the vertex expansion where the renormalization group flow of bosonic two-point functions is closed by means of skeleton equations (Dyson-Schwinger equations) and the superfluid order parameter is related to the single particle gap via a Ward identity. We explicitly calculate the chemical potential, the single-particle gap, and the superfluid order parameter at the unitary point and compare our results with experiments and previous calculations.