title: Tunable Polarons of Slow-Light Polaritons in a Two-Dimensional Bose-Einstein Condensate.
abstract: When an impurity interacts with a bath of phonons it forms a polaron. For increasing interaction strengths the mass of the polaron increases and it can become self-trapped. For impurity atoms inside an atomic Bose-Einstein condensate (BEC) the nature of this transition is not understood. While Feynman's variational approach to the Fröhlich model predicts a sharp transition for light impurities, renormalization group studies always predict an extended intermediate-coupling region characterized by large phonon correlations. To investigate this intricate regime and to test polaron physics beyond the validity of the Fröhlich model we suggest a versatile experimental setup that allows us to tune both the mass of the impurity and its interactions with the BEC. The impurity is realized as a dark-state polariton (DSP) inside a quasi-two-dimensional BEC. We show that its interactions with the Bogoliubov phonons lead to photonic polarons, described by the Bogoliubov-Fröhlich Hamiltonian, and make theoretical predictions using an extension of a recently introduced renormalization group approach to Fröhlich polarons.
authors.affiliation: Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Germany.|Graduate School Materials Science in Mainz, Gottlieb-Daimler-Strasse 47, 67663 Kaiserslautern, Germany.|Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: Fabian
authors.initials: F
authors.lastname: Grusdt
authors.affiliation: Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Fleischhauer