Toward high temperature quantum anomalous Hall effect through interface engineering

The experimental realization of quantum anomalous Hall effect (QAHE), i.e. the observation of quantized Hall resistance and zero longitudinal resistance in the absence of an external magnetic field, remained elusive for a long time after its theoretical prediction (Yu.R. et al, Science, 329, 61-64, (2010)). It was first observed in magnetically doped topological insulators (Zhang. C.Z. et al, 340,167-170 (2013)). One of the main hinderances in observing QAHE has been material defects. Until now, methods such as band engineering, gating effects and modulation doping have been employed to overcome this problem. A major contributor to defects which has been overlooked so far in observing QAHE, is chemical and structural mismatch between the substrate and the sample. In this talk, we will show that the film quality can be substantially improved by introducing a structurally and chemically matched buffer layer. We will further discuss whether this new interface engineering scheme can also help boost the operation temperature of QAHE beyond the present limitation (~1K).