Dresden 2026 – scientific programme

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O: Fachverband Oberflächenphysik

O 41: Topology and symmetry protected materials & Topological insulators – Poster (joint session O/TT)

O 41.2: Poster

Tuesday, March 10, 2026, 14:00–16:00, P2

Deciphering the complex surface of the topological phase in the polar semiconductor BiTeI — •Adrian Weindl, Christoph Setescak, and Franz J. Giessibl — Faculty of Physics, University of Regensburg, D-93053 Regensburg, Germany

BiTeI is a semiconductor consisting of polar layers that can form Rashba spin-split p-n junctions on its surface due to stacking faults. It has been shown that gentle annealing can transform the surface of BiTeI into a topological insulator with spin-polarized surface modes exhibiting linear dispersion. Previous LEED and RHEED measurements revealed that the surface undergoes a structural change from a non-centrosymmetric triple-layer structure to a quintuple-layer structure. However, the exact surface structure remains elusive. Using scanning tunneling microscopy, atomic force microscopy, and Kelvin probe force spectroscopy we study the surface before and after annealing with atomic resolution. We show that the annealing results in different surface phases that are highly sensitive to the annealing temperature: a chemically homgeneous phase at around 240°C and a inhomogeneous phase with strong charge disorder at 250°C. We determine the termination of each phase and confirm that the surface exhibits the signature of a topological surface state even in the strongly disordered phase.

Keywords: Atomic Force Microscopy; Scanning Tunneling Microscopy; Topological Insulators