Decay, scattering, and decoherence in many-body quanum systems

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Under the specific scattering perspective of the Forschergruppe, we focus on systems where complex dynamics result from particle-particle interactions. In particular, we will study the paradigmatic cases of interacting bosons in optical lattices and the three-body Coulomb problem. Both these cases exhibit characteristic features of open quantum systems, such as the loss of particles to the multi-particle continuum, the exchange of energy with a probe particle or interaction-induced decoherence. We seek a microscopic theory for these phenomena.In the first part of the project, we will examine the decay of interacting bosons trapped inside an optical lattice, which may escape from the lattice by tunneling to the many-body continuum. For this purpose, we will pursue an approximate master-equation ansatz, but also rely on exact numerical techniques such as complex dilation, as we have already applied it to the three-body Coulomb problem.In the second part, we will study inelastic scattering from Bose-Einstein condensates (BECs) confined in small lattices, with the purpose of probing the BEC by a scattering particle without destroying the condensate. In particular, we want to understand how the regular, mixed, or chaotic phase-space structure underlying the BEC’s quantum dynamics is reflected in the scattering process and explore the possibility of a random matrix theory modeling.In the third part of the project, we will investigate the interaction-induced decay of atomic Bloch oscillations on tilted optical lattices, focusing on that regime where the many-body level statistics is chaotic. Specifically, we want to understand how these spectral properties control the loss of coherence.