Regensburg 2022 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 11: Topology: Quantum Hall Systems
TT 11.9: Talk
Tuesday, September 6, 2022, 11:45–12:00, H10
Observation of non-Hermitian topology in a multi-terminal quantum Hall device — •Kyrylo Ochkan1, Raghav Chaturvedi1, Viktor Könye1, Ewelina Hankiewicz2, Jeroen van den Brink1, Joseph Dufouleur1, and Cosma Fulga1 — 1IFW Dresden, Deutschland — 2Julius-Maximilians-Universität Würzburg, Deutschland
One of the simplest examples of non-Hermitian topology is encountered in the Hatano-Nelson (HN) model, a one-dimensional chain where the hopping in one direction is larger than in the opposite direction. We present here the first experimental observation of non-Hermitian topology in a quantum condensed-matter system. The measurements are done in a multi-terminal quantum Hall device etched in a high mobility GaAs/AlGaAs two-dimensional electron gas ring. The conductance matrix that connects the currents flowing from the active contacts to the ground with the voltage of the active contacts is topologically equivalent to the HN Hamiltonian.
In our device, we directly measure and evidence the non-Hermitian skin effect. We also compute for our experimental device two topological invariants that are found to be more robust than the Chern number. We finally use the unique properties of our system and continuously tune the system configuration between open and periodic boundary conditions.
We focus here on the experimental results, whereas the theoretical aspects of the non-Hermitian skin effect and the topological invariants will be discussed in another presentation.