Resolving the topological classification of bismuth with topological defects

Bismuth, due to its large spin-orbit coupling, plays a fundamental role in many topological materials. Yet the topological classification of pure Bismuth has remained, thus far, rather ambiguous. While some theoretical models indicate its trivial topological nature, other theoretical and experimental studies suggest non-trivial topological classifications, such as a strong or a higher order topological insulator. I will explain the origin for this ambiguity and present scanning tunneling microscopy and spectroscopy data in which we resolve the topological classification of Bismuth, as a strong topological insulator with weak indices, by spectroscopically mapping the response of its boundary modes to a topological defect in the form of a screw dislocation [1].  

[1] Nayak et. al., Sci. Adv., 5, eaax6996 (2019)