Functional renormalization group approach to the BCS-BEC crossover
Version of Record online: 19 JUL 2010
Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Annalen der Physik
Volume 522, Issue 9, pages 615–656, September 2010
How to Cite
Diehl, S., Floerchinger, S., Gies, H., Pawlowkski, J.M. and Wetterich, C. (2010), Functional renormalization group approach to the BCS-BEC crossover. Ann. Phys., 522: 615–656. doi: 10.1002/andp.201010458
- Issue online: 2 AUG 2010
- Version of Record online: 19 JUL 2010
- Manuscript Accepted: 2 JUN 2010
- Manuscript Received: 5 FEB 2010
- DFG. Grant Numbers: FOR 723, Gi 328/1-4 (Emmy-Noether program), Gi 328/5-1 (Heisenberg-Program)
- Strongly correlated fermions;
- phase transitions;
- condensation phenomena.
The phase transition to superfluidity and the BCS-BEC crossover for an ultracold gas of fermionic atoms is discussed within a functional renormalization group approach. Non-perturbative flow equations, based on an exact renormalization group equation, describe the scale dependence of the flowing or average action. They interpolate continuously from the microphysics at atomic or molecular distance scales to the macroscopic physics at much larger length scales, as given by the interparticle distance, the correlation length, or the size of the experimental probe. We discuss the phase diagram as a function of the scattering length and the temperature and compute the gap, the correlation length and the scattering length for molecules. Close to the critical temperature, we find the expected universal behavior. Our approach allows for a description of the few-body physics (scattering and molecular binding) and the many-body physics within the same formalism.