title: Quasiparticle Properties of a Mobile Impurity in a Bose-Einstein Condensate.
abstract: We develop a systematic perturbation theory for the quasiparticle properties of a single impurity immersed in a Bose-Einstein condensate. Analytical results are derived for the impurity energy, effective mass, and residue to third order in the impurity-boson scattering length. The energy is shown to depend logarithmically on the scattering length to third order, whereas the residue and the effective mass are given by analytical power series. When the boson-boson scattering length equals the boson-impurity scattering length, the energy has the same structure as that of a weakly interacting Bose gas, including terms of the Lee-Huang-Yang and fourth order logarithmic form. Our results, which cannot be obtained within the canonical Fröhlich model of an impurity interacting with phonons, provide valuable benchmarks for many-body theories and for experiments.
authors.affiliation: Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark.
authors.forename: Rasmus Søgaard
authors.initials: RS
authors.lastname: Christensen
authors.affiliation: School of Physics and Astronomy, Monash University, Victoria 3800, Australia.|Aarhus Institute of Advanced Studies, Aarhus University, DK-8000 Aarhus C, Denmark.
authors.forename: Jesper
authors.initials: J
authors.lastname: Levinsen
authors.affiliation: Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark.
authors.forename: Georg M
authors.initials: GM
authors.lastname: Bruun