High Chern number van der Waals magnetic topological insulator MnBi₂Te₄/hBN

The Chern insulators are materials featuring unidirectional metallic surface states due to their non-trivial band topology [1]. As these surface states conduct electricity without dissipation, these materials were proposed for the construction of high-efficiency interconnects in future miniaturized electronic devices [2]. However, the number of the surface states is determined by a topological invariant of the band structure called Chern number, which usually turns out to be 1. Therefore, the conductance of realistic interconnects that would be based on these Chern insulators is small, leading to a large contact resistance between them and the standard metallic electrodes [2]. As this presents a major bottleneck for the performance of proposed devices an method of increasing the Chern number is pivotal. However, the enhancement of the Chern number is normally complicated and has been realized in only a few structures by means of doping [3,4]. This can result in structures with Chern number as high as 5 [3,4], but with a downside of structural disorder inherent to doping [5].

In this talk a proposal for a simpler method of realization of a high Chern number material is given. The proposal is based on the construction of a van der Waals heterostructure in which thin films of recently discovered antiferromagnetic Chern insulator MnBi₂Te₄ [6] are interlaced by monolayers of hexagonal-BN (hBN). The proposal is backed up by the results of ab initio calculations of Hall conductivity and tight binding calculations of surface spectra of systems with two and three septuples thick MnBi₂Te₄ films separated by hBN monolayers, former in forced ferromagnetic state, and latter in natural antiferromagnetic. The results show that the Chern number in these structures is equal to the number of MnBi₂Te₄ films used to build up the heterostructure, and the result can furthermore be generalized to heterostructures built with thicker MnBi₂Te₄ films.

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

[2] S.C. Zhang and J. Wang. US patent: US9362227B2 (2016)

[3] G. Jiang et al., Chin. Phys. Lett. 35, 076802 (2018)

[4] Y.-F. Zhao et al., Nature 588, 419 (2020)

[5] I. Lee et al. Proc. Natl. Acad. Sci. 112, 1316 (2015)

[6] M. M. Otrokov et al. Nature 576, 416 (2019)