Nathan Goldman, Jerome Beugnon, Fabrice Gerbier
We propose and describe a realistic scheme to detect topological edge states in an optical lattice subjected to a synthetic magnetic field, based on a generalization of Bragg spectroscopy sensitive to angular momentum. We demonstrate that the excitation fraction produced by a well-designed laser probe provides an unambiguous signature, which highlights the presence of topological edge states and establishes their chiral nature. This signature is present for a variety of boundaries, from a hard wall to a smooth harmonic potential added on top of the optical lattice. We investigate the effects of angular momentum transfer, with and without changing the internal atomic state. The latter method allows to independently detect the weak signal from the selected edge states on a dark background. Our method therefore offers the unique possibility to visualize topological edge states using in situ imaging in optical lattices.
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http://arxiv.org/abs/1203.1246
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