title: Decoherence of Impurities in a Fermi Sea of Ultracold Atoms.
abstract: We investigate the decoherence of ^{40}K impurities interacting with a three-dimensional Fermi sea of ^{6}Li across an interspecies Feshbach resonance. The decoherence is measured as a function of the interaction strength and temperature using a spin-echo atom interferometry method. For weak to moderate interaction strengths, we interpret our measurements in terms of scattering of K quasiparticles by the Fermi sea and find very good agreement with a Fermi liquid calculation. For strong interactions, we observe significant enhancement of the decoherence rate, which is largely independent of temperature, pointing to behavior that is beyond the scattering of quasiparticles in the Fermi liquid picture.
authors.affiliation: Institut für Quantenoptik und Quanteninformation (IQOQI), Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria.|Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria.
authors.forename: Marko
authors.initials: M
authors.lastname: Cetina
authors.affiliation: Institut für Quantenoptik und Quanteninformation (IQOQI), Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria.|Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria.
authors.forename: Michael
authors.initials: M
authors.lastname: Jag
authors.affiliation: Institut für Quantenoptik und Quanteninformation (IQOQI), Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria.|Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria.
authors.forename: Rianne S
authors.initials: RS
authors.lastname: Lous
authors.affiliation: Institut für Quantenoptik und Quanteninformation (IQOQI), Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria.|Van der Waals-Zeeman Institute, Institute of Physics, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, Netherlands.
authors.forename: Jook T M
authors.initials: JT
authors.lastname: Walraven
authors.affiliation: Institut für Quantenoptik und Quanteninformation (IQOQI), Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria.|Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria.
authors.forename: Rudolf
authors.initials: R
authors.lastname: Grimm
authors.affiliation: Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark.
authors.forename: Rasmus S
authors.initials: RS
authors.lastname: Christensen
authors.affiliation: Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C, Denmark.
authors.forename: Georg M
authors.initials: GM
authors.lastname: Bruun