Quantum anomalous Hall effect in intrinsic magnetic topological insulator MnBi2Te4 (a joint Winton seminar)

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• Prof Yuanbo Zhang (Fudan University)
• Wednesday 28 June 2023, 14:00-15:00
• Small Lecture Theatre.

If you have a question about this talk, please contact Bo Peng.

In a magnetic topological insulator, nontrivial band topology conspires with magnetic order to produce exotic states of matter that are best exemplified by quantum anomalous Hall (QAH) insulators and axion insulators. Up till now, such magnetic topological insulators are obtained by doping topological insulators with magnetic atoms. The random magnetic dopants, however, inevitably introduce disorders that hinder further exploration of topological quantum effects in the material. We resolve this dilemma by probing quantum transport in MnBi2Te4 thin flake—a topological insulator with intrinsic magnetic order. In this layered van der Waals crystal, the ferromagnetic layers couple anti-parallel to each other, so bulk MnBi2Te4 is an antiferromagnet. Atomically thin MnBi2Te4, however, becomes ferromagnetic when the sample has odd number of septuple layers (a septuple layer represents a single structural unit in the out-of-plane direction). We observe zero-field QAH effect in a five-septuple-layer specimen; an external magnetic field further enhance the QAH quantization by forcing all layers to align ferromagnetically. MnBi2Te4 therefore becomes the first intrinsic magnetic topological insulator exhibiting QAH effect. The results establish MnBi2Te4 as an ideal arena for further exploring various topological phenomena.

If you would like to chat to the invited speaker, please email Rakesh Arul (ra554@cam.ac.uk)

This talk is part of the Theory of Condensed Matter series.

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