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TT: Fachverband Tiefe Temperaturen

TT 41: Matter at Low Temperature: Quantum Liquids, Bose-Einstein-Condensates, Ultra-cold Atoms

TT 41.6: Talk

Thursday, March 26, 2009, 15:15–15:30, HSZ 105

Condensate density of interacting Bosons at finite temperature: A Functional Renormalization Group calculation — •Christopher Eichler¹, Nils Hasselmann², and Peter Kopietz¹ — ¹Institut für Theoretische Physik, Universität Frankfurt, Max-von-Laue-Straße 1, 60348 Frankfurt, Germany — ²International Center for Condensed Matter Physics, Universidade de Brasilia, Caixa Postal 04667, 70910-900 Brasilia,DF, Brazil

We use the Functional Renormalization Group to study thermodynamics of 3-dimensional interacting bosons at finite temperature. Our calculation is based on a truncated vertex expansion and a momentum independent two-body interaction including wave function renormalization. In particular, we derive the renormalization group flow of the condensate density in the symmetry broken phase and explicitly calculate the critical exponent β. Our result for β agrees quite well with the accepted numerical value for the 3-dimensional XY universality class.