Subproject E3

Interfaces between Topological Quantum Gases in Tunable Optical Lattices

Prof. Dr. Leticia Tarruell

During the last decade ultracold atoms in optical lattices have emerged as an ideal platform for the realization and study of condensed-matter model systems. Recently, the ability to implement artificial gauge fields in optical lattices has opened the possibility to explore topological physics in this setting. Quantum gases give direct experimental access to model topological Hamiltonians, provide novel observables to probe them, and enable excellent control of interactions. In these aspects, they complement ideally traditional solid-state systems and can help to deepen our understanding of topological phases. In this proposal, we want to explore one of the fingerprints of topological physics: the existence of topologically protected edge modes at the interface between systems belonging to different topological classes. To this end, we will realize interfaces between two quantum gases due to their separation in domains in the presence of strong repulsive interactions. We will study phaseseparated potassium Bose-Bose and Bose-Fermi mixtures in topological Bloch bands generated via Floquet driving of tunable-geometry optical lattices. By adjusting the interactions using Feshbach resonances, we will analyze systematically possible interaction-induced heating effects. We will also exploit the annular geometries generated by the phase separation to realize transport experiments in samples analogous to Corbino disks. In collaboration with the theory groups of the Research Unit, we will then explore adequate schemes to populate and characterize topological edge modes at the interface between two phase-separated gases, and show evidence of their chirality. Finally, we will aim at demonstrating the topological robustness of the edge modes under the effect of external perturbations such as disorder.

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