Topological edge states with ultracold atoms carrying orbital angular momentum in a diamond chain

Pelegrí, G. and Marques, A. M. and Dias, R. G. and Daley, A. J. and Ahufinger, V. and Mompart, J. (2019) Topological edge states with ultracold atoms carrying orbital angular momentum in a diamond chain. Physical Review A, 99 (2). 023612. ISSN 1094-1622

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    Abstract

    We study the single-particle properties of a system formed by ultracold atoms loaded into the manifold of l=1 orbital angular momentum (OAM) states of an optical lattice with a diamond-chain geometry. Through a series of successive basis rotations, we show that the OAM degree of freedom induces phases in some tunneling amplitudes of the tight-binding model that are equivalent to a net π flux through the plaquettes. These effects give rise to a topologically nontrivial band structure and protected edge states which persist everywhere in the parameter space of the model, indicating the absence of a topological transition. By taking advantage of these analytical mappings, we also show that this system constitutes a realization of a square-root topological insulator. In addition, we demonstrate that quantum interferences between the different tunneling processes involved in the dynamics may lead to Aharanov-Bohm caging in the system. All these analytical results are confirmed by exact diagonalization numerical calculations.