Resolving the topological classification of bismuth using topological defects
· Invited
Abstract
The growing diversity of topological classes leads to ambiguity between classes that share similar boundary phenomenology. This is the status of bulk bismuth. Recent studies have classified it as either a strong or a higher-order topological insulator, both of which host helical modes on their boundaries. We resolve the topological classification of bismuth by spectroscopically mapping the response of its boundary modes to a screw-dislocation. We find that the one-dimensional mode, on step-edges, extends over a wide energy range and does not open a gap near the screw-dislocations. This signifies that this mode binds to the screw-dislocation, as expected for a material with nonzero weak indices. We argue that the small energy gap, at the time reversal invariant momentum L, positions bismuth within the critical region of a topological phase transition between a higher-order topological insulator and a strong topological insulator with nonzero weak indices.
Abhay Kumar Nayak et al, Science Advances, 5, eaax6996 (2019)
Abhay Kumar Nayak et al, Science Advances, 5, eaax6996 (2019)
*This study was supported by the United States–Israel Binational Science Foundation (BSF; grant number 2016389), the Helmsley Charitable Trust (grant number 2018PG-ISL006), the German-Israeli Foundation (GIF; I-1364-303.7/2016), and the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant agreement no. 678702).
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Presenters
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Haim Beidenkopf
- Weizmann Institute of Science