Dresden 2026 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 38: Topology and symmetry protected materials & Topological insulators – Poster (joint session O/TT)
TT 38.1: Poster
Tuesday, March 10, 2026, 14:00–16:00, P2
Manipulation of topological surface states by switchable molecules. — Lukas Staiger1, Jannis Leßmeister1, •Ralf Hemm1, Juliusz Wolny1, Volker Schünemann1, Martin Aeschlimann1, and Benjamin Stadtmüller2 — 1Department of Physics and Research Center OPTIMAS, RPTU University Kaiserslautern-Landau, 67633 Kaiserslautern, Germany — 2Institute of Physics, University of Augsburg, 86159 Augsburg, Germany
Three-dimensional topological insulators host spin-momentum-locked surface states protected by time-reversal symmetry, giving them potential for spintronic devices. Controlling these states remains challenging but is crucial for opening gaps, shifting the Dirac point and tailoring spin textures for applications. In our work, we utilize a monolayer of the spin-crossover complex Fe(phen)2(SCN)2 on the topological insulator Bi2Se3 to break the time-reversal symmetry of the substrate. Employing angle-resolved photoemission spectroscopy, we trace the evolution of the electronic structure as a function of molecular coverage and temperature. Despite a conspicuous energy shift and modified dispersion, there is no clear evidence for a band gap opening after deposition of a molecular monolayer. Concurrently, additional spectral weight from molecular orbitals emerges, and thermally and optically driven spin-crossover transitions in the Fe(phen)2(SCN)2 layer induce changes in the Dirac-point energy and spectral weight. Our findings demonstrate that a spin-crossover overlayer can quantitatively alter the dispersion of topological surface states, while allowing them to exist due to strong interactions between molecules and surfaces.
Keywords: Topological insulators; Bi2Se3; Spin-crossover molecules; Hybrid interfaces; Angle-resolved photoemission spectroscopy (ARPES)