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O: Fachverband Oberflächenphysik

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

O 23.3: Poster

Montag, 1. März 2021, 13:30–15:30, P

Observation of backscattering induced by magnetism in a topological edge state — •Berthold Jaeck^1,2, Yonglong Xie^1,3, Bogdan Andrei Bernevig¹, and Ali Yazdani¹ — ¹Princeton University, Joseph Henry Laboratories and Department of Physics, Princeton, USA — ²Present Address: The Hong Kong University of Science and Technology, Department of Physics, Clearwater Bay, Kowloon, Hong Kong — ³Present Address: Harvard University, Department of Physics, Cambridge, USA

We have investigated the effects of time-reversal symmetry breaking on the topological edge state of bismuth. Using spectroscopic imaging and spin-polarized measurements with the STM, we have compared quasiparticle interference (QPI), occurring in the edge state of a pristine bismuth bilayer with that occurring in the edge state of a bilayer, which is terminated by ferromagnetic iron clusters. Our experiments on the decorated bilayer edge reveal an additional QPI branch that can be associated with spin-flip scattering across the Brioullin zone center between time-reversal band partners. The observed QPI characteristics exactly match with theoretical expectations for a topological edge state, having one Kramer’s pair of bands. Our results provide further evidence for the non-trivial nature of bismuth and, in particular, demonstrate backscattering inside a helical topological edge state induced by broken TRS through local magnetism (1).

This work is supported by the ONR, the Moore foundation, NSF-DMR, NSF-MRSEC and the Humboldt foundation.

(1) B. Jäck et al., PNAS 117 (28), 16214-16218 (2020)