High Chern Number Quantum Anomalous Hall Effect in Magnetic Topological Insulator Multilayers*

The quantum anomalous Hall (QAH) effect is a two-dimensional topological insulating state that has quantized Hall resistance of h/Ce² and vanishing longitudinal resistance under zero external magnetic field, where C is called the Chern number. The resistance-free chiral edge current of the QAH insulators has been predicted to have potential applications for next-generation energy-efficient electronics and spintronics as well as topological quantum computation. The QAH effect was first realized in chromium(Cr)- doped topological insulator (TI) thin films in 2013 [1] and soon after in vanadium (V)-doped TI thin films [2]. More recently, the QAH effect has also been realized in exfoliated intrinsic magnetic TI, MnBi₂Te₄ flakes with odd number layers [3], and manually assembled moiré graphene [4] or transition metal dichalcogenides [5]. In my talk, I will introduce our recent progress on the high Chern number QAH effect in magnetic TI multilayers. We used molecular beam epitaxy (MBE) to grow magnetic TI/TI multilayers and realized the QAH effect with tunable Chern number C from 1 to 5. We found that the Chern number C can be tuned by varying either the magnetic doping concentration or the thickness of the interior magnetic TI layers [6]. We leveraged this progress to further synthesize a series of magnetic TI/TI penta-layer heterostructures with different Cr doping concentrations and observed a plateau-to-plateau phase transition between the C = 1 to C = 2 QAH insulators under zero magnetic field [7].

[1] Chang et al., Science 340, 167 (2013)

[2] Chang et al, Nature Mater. 14, 473(2015)

[3] Deng et al Science 367, 895 (2020)

[4] Serlin et al Science 367, 900 (2020)

[5] Li et al., arXiv:2107.01796  (2021)

[6] Zhao et al., Nature 588, 419 (2020)

[7] Zhao et al, arXiv:2109.11382  (2021)