Berlin 2024 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 55: Topology and Symmetry Protected Materials (joint session O/TT)

TT 55.2: Vortrag

Mittwoch, 20. März 2024, 15:15–15:30, HL 001

Quantifying the Electronic Structure of at the Boundary of Topological Insulators by Means of Combined STM and AFM — •Christoph S. Setescak¹, Adrian Weindl¹, Andrea Donarini², and Franz J. Giessibl¹ — ¹Institute of Experimental and Applied Physics, University of Regensburg, Universitätstraße 31, 93080 Regensburg, Germany — ²Institute of Theoretical Physics, University of Regensburg, Universitätstraße 31, 93080 Regensburg, Germany

We show that combined STM and AFM can characterize the surface electronic structure of topological insulators in the Bi2Se3-family. The electronic structure is described by an effective tight-binding Hamiltonian, which is derived from a GW-DFT calculation. A circumspect application of Bardeens model of tunneling current enables us to rigorously interpret tunneling spectroscopy experiments and thus identify characteristic points in the halfspace bandstructure. Furthermore, our experiments demonstrate, that spatially resolved maps of the local density of states can resolve individual electronic degrees of freedom energetically as well as spatially. We observed quasiparticle interference in the topological boundary mode of Bi2Te3 at one-dimensional defects, which enables us to quantify subtle hexagonal warping terms in the dispersion relation of the boundary mode. Our recent measurements, in combination with the ability to structurally characterize defects and the crystal structure at the picometer scale, underscore the potential of combined AFM and STM in exploring the evolution of topological phases amidst varying degrees of disorder.

Keywords: GW-DFT; Topological Insulators; Atomic Force Microscopy; Scanning Tunneling Microscopy; Tight-Binding