Projects
At the moment, we are conducting several projects on the physics of quantum anomalous Hall (QAH) 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 +RK = h/e2 ≃ 25.9 kΩ and -RK.
Furthermore, we are exploring the opportunity to use quantum dots on graphen to create single electron sources.
Projects are funded by the cluster of Excellence ML4Q as well as the CRC 1238.
Dynamic transport in QAH edge states
We are studying dynamical transport of excitations (plasmons) in QAH edge channels using radio-frequency (RF) signals. After having characterized their velocity and attenuation as well as investigated the breakdown of the QAH effect we are now exploring charge fractionalization. Furthermore, we plan to investigate the coupling of the edge states to superconducting resonators in theRF regime.
Static control of QAH edge states
As the propagation direction of the QAH edge state is defined by the films magnetization it can mostly be controlled by an external magnetic field. This, however, only allows global manipulation of the edge states. In order to gain control locally we explore the effect of current-induced magnetization switching. We aim to use this effect to create domain walls in the QAH devices. There, we could study the interaction and coupling of two co-propagating edge states using both DC as well as RF signals.
Heat transport of QAH edge states
Besides DC and RF measurements we established a setup to measure current-fluctuations on QAH devices. We aim to use the correlation between the amplitude of current-fluctuations and the devices temperature to observe heat transport mediated by the QAH edge states.