期刊
ACS NANO
卷 15, 期 8, 页码 13444-13452出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsnano.1c03936
关键词
magnetic topological insulator; thin film; MnBi2Te4; quantum anomalous Hall insulator; ferromagnetic insulator; angle-resolved photoemission spectroscopy
类别
资金
- ARC DECRA fellowship [DE160101157, CE170100039]
- International Synchrotron Access Program (ISAP)
- Australian Government
- ARC Centre for Future Low Energy Electronics Technologies (FLEET)
- DOE Office of Science User Facility [DE-AC02-05CH11231]
- Australian Research Council [DE160101157] Funding Source: Australian Research Council
This study used temperature-dependent angle-resolved photoemission spectroscopy to investigate ultrathin MnBi2Te4, revealing a temperature-dependent magnetic topological phase transition that can be achieved at higher temperatures.
Intrinsic magnetic topological insulators offer low disorder and large magnetic band gaps for robust magnetic topological phases operating at higher temperatures. By controlling the layer thickness, emergent phenomena such as the quantum anomalous Hall (QAH) effect and axion insulator phases have been realized. 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 ultrathin MnBi2Te4 has yet to be achieved. Critical to achieving the promise of this system is a direct measurement of the layer-dependent energy gap and verification of a temperature-dependent topological phase transition from a large band gap QAH insulator to a gapless TI paramagnetic phase. Here we utilize temperature-dependent angle-resolved photoemission spectroscopy to study epitaxial ultrathin MnBi2Te4. We directly observe a layer-dependent crossover from a 2D ferromagnetic insulator with a band gap greater than 780 meV in one septuple layer (1 SL) to a QAH insulator with a large energy gap (>70 meV) at 8 K in 3 and 5 SL MnBi2Te4. The QAH gap is confirmed to be magnetic in origin, as it becomes gapless with increasing temperature above 8 K.
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