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Ultracold atoms in optical lattices have proven to be an ideal testbed for simulating strongly correlated condensed matter physics. The microscopic understanding of the underlying Hamiltonian and precise control over the Hamiltonian parameters via external fields allow faithful realisation of interesting many-body systems that are otherwise hard to study theoretically or experimentally. This thesis addresses the issue of many-body decoherence, using analytical and numerical techniques, in these optical lattice experiments that arises due to coupling to the environment. We specifically study fermionic systems to investigate the effects of incoherent light scattering on the dynamics. Starting from the atomic structure of fermionic species that are experimentally relevant we provide a framework to derive a microscopic master equation and look at the regimes of strong interactions. The interplay between the atomic physics and many-body physics is found to give rise to interesting observations like suppression of the decoherence effect for magnetically ordered insulators that occur for strong repulsive interactions and an enhancement of the decoherence effect for the case of superfluid pairs that occur for strong attractive interactions. The master equation framework is then applied to a recent experiment looking at the effect of controlled decoherence on a many-body localised system of ultracold fermions in an optical lattice. We determine the dissipative processes in the system looking at the atomic structure of the fermionic species. Lastly we study a system of two species bosons to investigate the effect of interspecies interaction in terms of bipartite entanglement between the species, and how this impacts upon the visibility of the momentum distribution. This study proposes a solution to a recent experimental observation of effects on the momentum distribution of impurity atoms in a Bose-Einstein condensate that would not be explained by polaronic behaviour alone. |
