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Partial lattice defects in higher-order topological insulators

Raquel Queiroz, Weizmann Institute of Science

I will show that higher-order topological insulators (HOTIs) can host a single helical mode along screw or edge dislocations in the absence of weak topological indices. Unlike in weak topological insulators (WTI), the helical modes of HOTIs are necessarily bound to a dislocation characterized by a fractional Burgers vector, macroscopically detected by the existence of stacking faults. The robustness of a helical mode on a partial defect is demonstrated by an adiabatic transformation that restores translation symmetry in the stacking fault. Since partial defects and stacking faults are commonplace in bulk crystals, the existence of such helical modes can measurably affect the expected conductivity in these materials.

Finally, I will briefly discuss the modes bound to lattice defects of bismuth, and what they can teach us about its topology.

[1] R. Queiroz et al., Phys. Rev. Lett. 123, 266802 (2019).


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