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SUMMARY:Quantum anomalous Hall effect in intrinsic magnetic topological in
 sulator MnBi2Te4 (a joint Winton seminar) - Prof Yuanbo Zhang (Fudan Unive
 rsity)
DTSTART:20230628T130000Z
DTEND:20230628T140000Z
UID:TALK202744@talks.cam.ac.uk
CONTACT:Bo Peng
DESCRIPTION: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 ins
 ulators. Up till now\, such magnetic topological insulators are obtained b
 y doping topological insulators with magnetic atoms. The random magnetic d
 opants\, however\, inevitably introduce disorders that hinder further expl
 oration of topological quantum effects in the material. We resolve this di
 lemma by probing quantum transport in MnBi2Te4 thin flake—a topological 
 insulator with intrinsic magnetic order. In this layered van der Waals cry
 stal\, the ferromagnetic layers couple anti-parallel to each other\, so bu
 lk MnBi2Te4 is an antiferromagnet. Atomically thin MnBi2Te4\, however\, be
 comes ferromagnetic when the sample has odd number of septuple layers (a s
 eptuple layer represents a single structural unit in the out-of-plane dire
 ction). We observe zero-field QAH effect in a five-septuple-layer specimen
 \; an external magnetic field further enhance the QAH quantization by forc
 ing 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.\n\n\nIf you would like to chat to the invited spea
 ker\, please email Rakesh Arul (ra554@cam.ac.uk)
LOCATION:Small Lecture Theatre
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