title: Renormalization group approach to the Fröhlich polaron model: application to impurity-BEC problem.
abstract: When a mobile impurity interacts with a many-body system, such as a phonon bath, a polaron is formed. Despite the importance of the polaron problem for a wide range of physical systems, a unified theoretical description valid for arbitrary coupling strengths is still lacking. Here we develop a renormalization group approach for analyzing a paradigmatic model of polarons, the so-called Fröhlich model, and apply it to a problem of impurity atoms immersed in a Bose-Einstein condensate of ultra cold atoms. Polaron energies obtained by our method are in excellent agreement with recent diagrammatic Monte Carlo calculations for a wide range of interaction strengths. They are found to be logarithmically divergent with the ultra-violet cut-off, but physically meaningful regularized polaron energies are also presented. Moreover, we calculate the effective mass of polarons and find a smooth crossover from weak to strong coupling regimes. Possible experimental tests of our results in current experiments with ultra cold atoms are discussed.
authors.affiliation: 1] Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Germany [2] Graduate School Materials Science in Mainz, Gottlieb-Daimler-Strasse 47, 67663 Kaiserslautern, Germany [3] Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: F
authors.initials: F
authors.lastname: Grusdt
authors.affiliation: 1] Russian Quantum Center, Skolkovo 143025, Russia [2] Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: Y E
authors.initials: YE
authors.lastname: Shchadilova
authors.affiliation: 1] Department of Physics, Moscow State University, 119991 Moscow, Russia [2] Russian Quantum Center, Skolkovo 143025, Russia.
authors.forename: A N
authors.initials: AN
authors.lastname: Rubtsov
authors.affiliation: Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: E
authors.initials: E
authors.lastname: Demler