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HL: Fachverband Halbleiterphysik

HL 14: Poster II

HL 14.26: Poster

Monday, March 18, 2024, 15:00–18:00, Poster F

Investigation of quantum anomalous Hall edge states using thermal noise measurements — •Alina Rupp, Daniel Rosenbach, Boris Stanchev, Anjana Uday, Gertjan Lippertz, Alexey Taskin, Yoichi Ando, and Erwann Bocquillon — Physics Institute II, University of Cologne, Cologne, Germany

In 3D topological insulators (TIs) transport is governed by 2D topologically protected surface states. By magnetically doping the TI quantum anomalous Hall insulators can be created which exhibit a single chiral edge state and a quantized Hall conductance. Besides the electronic transport, heat transport is also quantized. We aim to observe this using thermal noise measurements.
As a basis for our experiment, we use thin films of V-doped (Bi_xSb_1−x)₂Te₃ grown by molecular beam epitaxy which are etched into a bow tie shape. In the center of the bow tie, we define a metallic island that is heated via the Joule effect through one edge channel while through another edge channel the heat is evacuated. Due to the conductance quantization the Joule power heating the island is well defined, while the quantization of heat transport controls the rate at which this power is evacuated from the island. Thus, by measuring the temperature of the island using thermal noise, insights on the characteristics of the edge states can be gained. In order to detect small changes in the temperature we combine an LC resonator with low-noise amplifiers to enhance the measured signal. This setup has to be calibrated in terms of the amplification chain and the electron temperature to then be able to detect quantized heat transport.

Keywords: quantum anomalous Hall; noise measurements; heat transport; topological insulators