Regensburg 2019 – scientific programme

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MA: Fachverband Magnetismus

MA 33: Focus Session: Topology in 3D Reciprocal Space: Beyond Dirac and Weyl Quasiparticles (joint session TT/MA)

MA 33.3: Invited Talk

Wednesday, April 3, 2019, 16:00–16:30, H2

Direct optical detection of Weyl fermion chirality in a topological semimetal — •Nuh Gedik — Department of Physics, Massachusetts Institute of Technology, Cambridge, MA USA

A Weyl semimetal is a novel topological phase of matter, in which Weyl fermions arise as pseudo-magnetic monopoles in its momentum space. The chirality of the Weyl fermions, given by the sign of the monopole charge, is central to the Weyl physics, since it serves as the sign of the topological number and gives rise to exotic properties such as Fermi arcs and the chiral anomaly. In this talk, I will present our recent measurements in which we directly detect the chirality of the Weyl fermions by measuring the photocurrent in response to circularly polarized mid-infrared light. The resulting photocurrent is determined by both the chirality of Weyl fermions and that of the photons. Beyond Weyl semimetals, these experiments establish nonlinear photocurrent spectroscopy as a powerful tool for studying the geometrical properties of the electronic wavefunction in quantum materials. To this end, I will also discuss how we used this method to reveal electrically switchable Berry curvature dipole in the monolayer topological insulator WTe2.