Decoherence and absorption spectra of impurities in ultracold quantum gases

We study the finite-mass corrections to the non-equilibrium dynamics of an impurity in a gas of lattice fermions after an interaction quench. Our emphasize is on the question under which conditions a heavy impurity immersed in a Fermi liquid is subject to the orthogonality catastrophe and complete loss of coherence. We calculate the time-dependent Ramsey interference signal using a novel hybrid approach which combines path integral and functional determinant methods. We find that a finite quasiparticle peak persists in d ? 2 in agreement with previous work and explore the influence of finite temperature and system size. Using our microscopic approach we study also the time evolution of a Bose-Einstein-Condensate after the excitation of a Rydberg atom and the formation of a sequence of giant molecular bound states. Our calculation reveals the emergence of a novel type of orthogonality catastrophe present in coupled BEC-Rydberg systems. We determine the absorption spectra of the system and we predict the non-equilibrium time evolution of various experimentally measurable observables following the sudden excitation of the Rydberg state and discuss possible experimental implementations.