Berlin 2024 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 29: Quantum Transport and Quantum Hall Effects

HL 29.3: Talk

Wednesday, March 20, 2024, 10:15–10:30, EW 561

Microwave transport in quantum anomalous Hall edge states — •Torsten Röper, Hugo Thomas, Daniel Rosenbach, Christian Dickel, Anjana Uday, Gertjan Lippertz, Alexey Taskin, Yoichi Ando, and Erwann Bocquillon — Physics Institute II, University of Cologne, Cologne, Germany

Magnetically doped topological insulators such as V-doped (Bi_xSb_1−x)₂Te₃ (V-BST) show the quantum anomalous Hall (QAH) effect. These materials exhibit a quantized Hall conductance without an applied external magnetic field, owing to the presence of a non-zero Chern number. A single chiral edge state emerges at the edge of the QAH material and is topologically protected against disorder and perturbations. Microwave transport in chiral edge states allows for investigating the dispersion and velocity of the edge states.

In this context, we conduct microwave measurements on devices using V-BST films grown by molecular beam epitaxy. We measure the transmission of the edge states as a function of temperature, magnetic field and frequency. We determine their velocity and attenuation from the phase and amplitude, respectively. Following recent works, we ascribe the interaction with charge puddles as a primary source of dissipation. We describe this interaction with a circuit model and observe a dispersion consistent with findings in similar materials. As such, it provides a potential material platform for coherent electronic transport in chiral edge states and the generation and manipulation of flying Majorana excitations.

Keywords: Quantum anomalous Hall; Microwave transport; Topological insulator; Plasmons; Majorana physics