Heidelberg 2015 – scientific programme
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A: Fachverband Atomphysik
A 23: Ultra-cold atoms, ions and BEC IV (with Q)
A 23.4: Talk
Wednesday, March 25, 2015, 15:15–15:30, C/HSW
Solution of the Fröhlich polaron problem at intermediate couplings — •Fabian Grusdt1,2,3, Yulia E. Shchadilova4,3, Alexey N. Rubtsov5,4, and Eugene Demler3 — 1Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Germany — 2Graduate School Materials Science in Mainz, Kaiserslautern, Germany — 3Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA — 4Russian Quantum Center, Skolkovo 143025, Russia — 5Department of Physics, Moscow State University, 119991 Moscow, Russia
We develop a renormalization group approach for analyzing Fröhlich polarons and apply it to a problem of impurity atoms immersed in a Bose-Einstein condensate (BEC) of ultra cold atoms. Polaron energies obtained by our method are in excellent agreement with recent diagrammatic Monte Carlo calculations [Vlietinck et al., arXiv:1406.6506] for a wide range of interaction strengths. We show analytically that the energy of the Fröhlich polaron in a BEC is logarithmically UV divergent, and present a regularization scheme. This allows us to make predictions for the polaron energy, which can be tested in future experiments. Furthermore we calculate the effective mass of polarons and find a smooth crossover from weak to strong coupling regimes. Our method can be generalized to non-equilibrium polaron problems.