Angle-resolved photoemission spectroscopy (ARPES) is one of the most powerful tools to study the electronic properties of solids. Besides providing a wealth of information on the momentum-dependent band structure, the impressive progress in high-resolution and multi-dimensional ARPES allows insights into the nature of the quantum states in the solid itself. In this talk, we will discuss how topological properties like Berry curvature and orbital angular momentum are manifest in circular dichroism in ARPES. Based on an intuitive wave-packet description and corroborated by state-of-the-art first-principle calculations, we demonstrate how momentum-resolved Berry curvature can be mapped out for prototypical two-dimensional materials. 
Furthermore, topological properties can be induced by tailored light. In particular, graphene pumped by circularly polarized light is the paradigmatic example of such a Floquet-Chern insulator. Extending the concept of circular dichroism to the time domain, we show how this transient topological state can be traced by time-resolved ARPES.  

References:
[1] M. Schüler, U. De Giovannini, H. Hübener, A. Rubio, M. Sentef, P. Werner, Sci. Adv. 6, eaay2730 (2020)
[2] M. Schüler, U. De Giovannini, H. Hübener, A. Rubio, M. Sentef, T. Devereaux,  P. Werner, arXiv:2003.11621 [cond-mat] (2020)

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