Detroit, MI 48201
Speaker: Dr. Ching-Kit (Chris) Chan, University of California, Los Angeles
Title: Driving Dirac and Weyl Materials
Thursday, March 2, 2017
Snacks at 3:30 pm. Colloquium at 3:45 pm.
Abstract: The discovery of topological materials revolutionized condensed matter physics over the last decade. The topological richness of the electronic band structure brings in many exotic physical properties such as topological robustness, bulk-edge correspondence and quantum anomalies. Collaborative efforts between theorists and experimentalists in this research area have led to remarkable developments from fundamental understanding of topological phases to material applications. Discovering and manipulating topological matter is one of the most exciting research directions in condensed matter physics nowadays.
These excitements are further elevated by recent progresses in laser-driven topological materials. It is typically difficult to understand physical systems driven far away from equilibrium. However, when a material is driven periodically in time, a well-defined quasi-Hamiltonian exists which permits equilibrium descriptions and fruitful concepts borrowed from solid state physics. The corresponding quasi-energies, known as the Floquet bands, are analogous to Bloch bands in lattice crystals with spatial periodicity. In this Colloquium, I will first review the current experimental situation on the observation of Floquet-Bloch bands by laser-driving 2D Dirac electrons on the surface of a 3D topological insulator. I will then discuss theoretical proposals of driving the 3D generalization---Weyl fermions in semimetal materials. We shall see how the coupling between chiral fermions and chiral photons induces interesting anomalous transport effects and topological phase transitions. I will also present a photogalvanic application of Weyl semimetals for detecting infrared radiations.