Title: Ultracold atoms carrying orbital angular momentum in lattices of rings

Speaker: Professor Verónica Ahufinger, Universitat Autònoma de Barcelona, Spain

Abstract:
Tunnelling is one of the paradigms of quantum mechanics and its control in the context of ultracold neutral atoms has been, recently, a topic of intense research. In this seminar, we will consider a system formed by non-interacting ultracold atoms loaded into the manifold of l = 1 Orbital Angular Momentum (OAM) states of a diamond lattice, in which complex tunnelling amplitudes appear naturally [1]. Through a series of successive basis rotations [2,3], we show that the OAM degree of freedom induces phases in some tunnelling amplitudes of the tightbinding model that are equivalent to a net π flux through the plaquettes and give rise to a topologically non-trivial band structure and protected edge states. In addition, we demonstrate that the system also exhibits Aharonov-Bohm caging, which consists of the confinement of specifically prepared wave packets due to quantum interference. We will also show the experimental observation of Aharonov-Bohm caging using OAM modes in a system of coupled optical waveguides forming a diamond structure [4].

[1] J. Polo, J. Mompart and V. Ahufinger, Geometrically induced complex tunnelings for ultracold atoms carrying orbital angular momentum. Phys. Rev. A 93, 033613 (2016).
[2] G. Pelegrí, A. M. Marques, R. G. Dias, A. J. Daley, V. Ahufinger and J. Mompart, Topological edge states with ultracold atoms carrying orbital angular momentum in a diamond chain. Phys. Rev. A 99, 023612 (2019).
[3] G. Pelegrí, A. M. Marques, R. G. Dias, A. J. Daley, J. Mompart and V. Ahufinger, Topological edge states and Aharonov-Bohm caging with ultracold atoms carrying orbital angular momentum. Phys. Rev. A 99, 023613 (2019).
[4] C. Jörg, G. Queraltó, M. Kremer, G. Pelegrí, J. Schulz, A. Szameit, G. von Freymann, J. Mompart and V. Ahufinger, Artificial gauge field switching using orbital angular momentum modes in optical waveguides. Light: Science & Applications 9, 150 (2020).

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