The material MnBi2Te4 is an antiferromagnet that can, in thin-film form, support interesting topological states. Ge et al. investigated the transport properties of MnBi2Te4 films 7 to 10 layers thick in the presence of a magnetic field. The authors showed that the films were in the so-called Chern insulator state, exhibiting quantized conductance that could not be explained by the ordinary quantum Hall effect. The thinner, seven-layer samples had a Chern number of 1, whereas the 9- and 10-layer samples were in an even more exotic state with a Chern number of 2. The tuning of the Chern number with sample thickness was also supported by numerical calculations.
Natl. Sci. Rev. 10.1093/nsr/nwaa089 (2020).