Quantum Anomalous Hall Effect in Sub-Micrometer-Size Devices

The quantum anomalous Hall (QAH) effect is the zero magnetic field manifestation of the integer quantum Hall effect. The QAH effect is usually realized in mechanically scratched millimeter-size magnetically-doped topological insulator (TI) devices. However, to access the potential applications of the QAH phenomenon, the nanofabrication of small QAH devices within quantum coherent length is essential. In this talk, we will introduce our recent progress on sub-micrometer-size QAH devices. Based on our macroscopic molecular beam epitaxy grown magnetically doped TI films, we used electron-beam lithography to fabricate the Hall bar devices within a width range from 10μm to 100nm. We found the QAH effect still survives in the Hall bar devices with a width of ~100 nm. Moreover, we found that the  Hall resistance plateau which usually corresponds to the magnetic exchange gap size becomes narrower with reducing the Hall bar width. By combining theoretical calculations, we demonstrate that the narrower Hall resistance plateau is because of the interaction effect between two chiral edge channels in sub-micrometer-size Hall bar devices. Our results open a new route to study the spatial distribution of the QAH chiral edge states and pave the way for the potential applications of the QAH phenomenon.