Correlated energy transfer between two ultracold atomic species

We study a single atom as an open quantum system, which is initially prepared in a coherent state of low energy and oscillates in a one-dimensional harmonic trap through an interacting ensemble of $N_A$ bosons, held in a displaced trap [{\it arXiv:1410.8676}]. The non-equilibrium quantum dynamics of the total system is simulated by means of an {\it ab-initio} method, giving us access to all properties of the open system and its finite environment. In this talk, we focus on unraveling the interplay of energy exchange and correlations between the subsystems, which are coupled in such a spatio-temporally localized manner. We show that an inter-species interaction-induced level splitting accelerates the energy transfer between the atomic species for larger $N_A$, which becomes less complete at the same time. System-environment correlations prove to be significant except for times when the excess energy distribution among the subsystems is highly imbalanced. These correlations result in incoherent energy transfer processes, which accelerate the early energy donation of the single atom. By analyzing correlations between intra-subsystem excitations, certain energy transfer channels are shown to be (dis-)favored depending on the instantaneous direction of transfer.