Intrinsic magnetic topological insulators offer the potential of low disorder and large magnetic bandgaps for robust magnetic topological phases operating at higher temperatures, enabling observation of phenomena such as the quantum anomalous Hall effect (QAHE) and axion insulator phases [1,2]. However, these observations occur at temperatures significantly lower than the Neel temperature of bulk MnBi2Te4, and measurement of the magnetic energy gap at the Dirac point in ultra-thin MnBi2Te4 has yet to be achieved.
Here we utilise temperature dependent angle-resolved photoemission spectroscopy to study epitaxial ultra-thin MnBi2Te4. We directly observe a layer dependent crossover from a 2D ferromagnetic insulator to a QAH insulator. The QAH gap is confirmed to be magnetic in origin, as it abruptly diminishes with increasing temperature above 8 K. The direct observation of a large magnetic energy gap in the QAH phase of few-SL MnBi2Te4 is promising for further increasing the operating temperature of QAH materials.
1. Deng, Y. et al. Quantum anomalous Hall effect in intrinsic magnetic topological insulator MnBi2Te4. Science 367, 895-900 (2020).
2. Liu, C. et al. Robust axion insulator and Chern insulator phases in a two-dimensional antiferromagnetic topological insulator. Nature Mater. 19, 522 (2020).
About the presenter
Dr Chi Xuan Trang is an expert in molecular beam epitaxy growth (MBE) and angle-resolved photoelectron spectroscopy (ARPES) of topological materials. Within FLEET, she will work with AI Mark Edmonds on the growth of 2D topological systems such as intrinsic magnetic topological insulators and topological superconductors and study their electronic structure using ARPRES-Toroidal Analyser facilities at the Australian Synchrotron and the Advanced Light Source (Berkeley).
Dr Trang works within FLEET’s Research theme 1 and Enabling technologies A