Regensburg 2022 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 18: Topological Insulators

TT 18.5: Talk

Wednesday, September 7, 2022, 10:30–10:45, H23

Stacking faults in weak topological insulators with time reversal symmetry — •Gabriele Naselli, Viktor Könye, and Ion Cosma Fulga — Leibniz-Institut für Festkörper-und Werkstoffforschung, Dresden, Germany

In experimental observation stacking faults can play a significant role in hiding the topological properties of topological insulators. The defects break lattice symmetries which can be required for the protection of the topological states in weak topological insulators. We studied stacking faults in 3D weak topological insulators like Bi₂TeI and Bi₁₄Rh₃I₉. Both these materials are formed by 2D topological insulating layers (with time reversal symmetry and quantum spin Hall effect) stacked on top of each other in the z direction with trivial insulating spacers between them. We have built a simple tight binding model for both of these materials and got the topological properties solving the eigenvalue problem numerically. We introduced a stacking fault in our model by shifting half of the system by a fraction of the unit cell in the z direction. We mapped the stacking surface in the WTI into a Su-Schrieffer-Heeger chain, considering the effective hoppings between the TI layers on the left and right side of the stacking fault. When all the TI layers on the left side are strongly interacting with the TI layers on the right side of the defect the corresponding SSH model is in the trivial phase and we did not find conducting states. Instead when the stacking fault has two weakly interacting TI layers at its boundaries the corresponding SSH chain is in the topological phase and we have found localized conducting states at the defect.