SurfaceScience21 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 23: Poster Session II: Topology and symmetry-protected materials

O 23.1: Poster

Montag, 1. März 2021, 13:30–15:30, P

Discovery of chiral topological semimetals with multifold fermions and long surface Fermi-arcs — •Niels B. M. Schröter — Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland

Chiral topological semimetals (which possess neither mirror nor inversion symmetries) are a new family of topological materials that are expected host numerous novel phenomena, such as multifold fermions with large topological charge, long Fermi-arc surface states, and a quantized response to circularly polarized light. However, until recently, all known topological semimetals crystallized in space groups that contain mirror operations, which means that the aforementioned phenomena must vanish.

Here, I will present evidence from angle-resolved photoelectron spectroscopy that a family of chiral intermetallic catalysts, including PtAl and PdGa, are chiral topological semimetals. We directly visualize the multifold fermions in these compounds and show that they carry the largest possible Chern number that can be realized in any solid by imaging their extremely long surface Fermi-arcs and resolving a spin-orbit coupling induced band splitting. We also show experimentally that there is a direct relationship between the handedness of the crystal structure and the electronic chirality (i.e. the Chern number sign) of the multifold fermions. This finding demonstrates that structural chirality can be used as a control parameter to manipulate phenomena that are sensitive to electronic chirality, such as the direction of topological photocurrents.