Interacting cold-atomic gases in optical lattices offer an experimental approach to outstanding problems of many body physics. One important example is the interplay of interaction and topology which promises to generate a variety of exotic phases such as the fractionalized Chern insulator or the topological Mott insulator. Both theoretically understanding these states of matter and finding suitable systems that host them have proven to be challenging problems. Here we propose a cold-atom setup where Hubbard on-site interactions give rise to spin liquid-like phases: weak and strong topological Mott insulators. They represent the celebrated paradigm of an interacting and topological quantum state with fractionalized spinon excitations that inherit the topology of the non-interacting system. Our proposal shall help to pave the way for a controlled experimental investigation of this exotic state of matter in optical lattices. Furthermore, it allows for the investigation of a dimensional crossover from a two-dimensional quantum spin Hall insulating phase to a three-dimensional strong topological insulator by tuning the hopping between the layers.
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The authors are grateful to Karyn Le Hur for early discussions on the project and acknowledge Walter Hofstetter, Daniel Cocks, Michael Buchhold, and Karyn Le Hur for previous collaborations on related topics. The Young Investigator Group of P.P.O. received financial support from the "Concept for the Future" of the Karlsruhe Institute of Technology (KIT) within the framework of the German Excellence Initiative. S.R. is supported by the DFG through FOR 960, the DFG priority program SPP 1666 "Topological Insulators", by the DFG through SFB 1143, and by the Helmholtz association through VI-521. We acknowledge support by the Deutsche Forschungsgemeinschaft and the Open Access Publishing Fund of Karlsruhe Institute of Technology (KIT).