FLEET PhD student Qile Li
The recently discovered anti-ferromagnetic topological insulator MnBi2Te4 (MBT) has been proved to host rich topological phases such as quantum anomalous Hall (QAH) and axion insulator phase in its thin films. A transition from a large gap 2D Ferromagnetic (FM) insulator in 1 Septuple layer (SL) to 5SL QAH insulator has been reported [1]. 1SL MBT has a wide gap exceeding 700meV and the robust FM originates from the deep underlying Mn 3d levels with a Curie temperature of 20K.
The excellent compatibility of 1SL MBT with 3D TI Bi makes MBT/BT heterostructures promising platform for realising of novel topological phases such as Quantum anomalous Hall insulator and axion insulators. The minimal lattice mismatch between Bi2Te3 and MBT guarantees negligible interface potential difference, therefore a large exchange gap in the surface state is expected because the extended surface state from Bi2Te3 strongly couples to magnetic moments from Mn ions [2]. These van der waals heterostructures involve much less magnetic disorder due to their stoichiometric structures and the Curie temperature is much higher than conventional magnetic dilute doped 3D TIs.
In this study, we probe the band structures of several MBT-BT heterostructures using angle resolved photoelectron spectroscopy. We have observed that the surface of MBT/BT/MBT heterostructure hosts hexagonal warped massive Dirac Fermion with a magnetic gap of 50meV, in excellent agreement with DFT calculations. The engineering of massive Dirac Fermion in the MBT/BT heterostructures opens up the possibility of applications in topological quantum computing and spintronics.
1 Trang et al., arXiv:2009.06175
2 Otrokov et al., 2D Mater. 4, 025082 (2017)
About the presenter
Qile Li works with Dr Mark Edmonds at Monash University on the growth of 2D materials and characterisation of them by the ARPES technique. He is working on the characterisation of electronic structures of Quantum Anomalous insulators (e.g. MnBi2Te4), and QAH insulator/topological insulator heterostructures. He is working within Research Theme 1: Topological Dissipationless Systems investigating the effects of film thickness and magnetism on the electronic structure such as surface states of topological materials in the search for a large-gap QAH insulator. Qile is interested in both theory (model Hamiltonians) and experiments (characterisation of topological materials, strongly correlated materials).