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At the moment, we plan to conduct several projects on the physics of quantum anomalous insulators. Electron transport in these ferromagnetic topological insulators is governed by a single ballistic edge state propagating in a direction set by the magnetization. Impressively, ferro-magnetism then manifests as a Hall resistance hysterically cycling between +R= h/e≃ 25.9 kΩ and -RK.

If you are interested to join any of the following projects, please contact us at bocquillonSpamProtectionph2.uni-koeln.de!

Several research directions are envisioned, with support funding from the ERC, the cluster of Excellence ML4Q, the CRC 1238.

Static control of QAH edge states

Our aim is here to gain in-situ control of the edge state configuration by locally creating magnetic field offsets or gradients using ferromagnetic islands to create domain walls in the QAH layer, between domains of opposite magnetization. At the created domain walls, two QAH edge states should co-propagate and we plan to study via DC and RF transport methods how ohmic or capacitive charge transfer can occur at the interface.

Dynamic transport in QAH edge states

We will study dynamical transport of excitations (plasmons) in QAH edge channels, and first characterize their velocity and attenuation. We will search for signatures of coupling to magnon modes and assess the performances of miniaturized non-reciprocal microwave components.

Interfaces between QAH edge states and superconductors

When superconductivity is induced in a QAH edge state via the proximity effect, new excitations called chiral edge vortices appear, which have a Majorana character. They have extremely peculiar properties and in particular follow anyonic statistics. We would like to evidence these quasiparticles and their properties using a combination of low-frequency and high-frequency (GHz) techniques.