Materials with ferroelectrically switchable topological properties are of interest for both fundamental physics and practical applications. Using first-principles calculations, we find that stacking ferroelectric α-In2Se3 monolayers into a bilayer leads to polarization-dependent band structures, which yields polarization-dependent topological properties. Specifically, we find that the states with interlayer ferroelectric couplings are quantum spin Hall insulators, while those with antiferroelectric polarizations are normal insulators. We further find that In2Se3 trilayer and quadlayer exhibit nontrivial band topology as long as in the structure the ferroelectric In2Se3 bilayer is antiferroelectrically coupled to In2Se3 monolayers or other ferroelectric In2Se3 bilayer. Otherwise the system is topologically trivial. The reason is that near the Fermi level the band structure of the ferroelectric In2Se3 bilayer has to be maintained for the nontrivial band topology. This feature can be used to design nontrivial band topology for the thicker films by a proper combination of the interlayer polarization couplings. The topological properties can be ferroelectrically tunable using the dipole locking effect. Our study reveals switchable band topology in a family of natural ferroelectrics, which provide a platform for designing new functional devices.
@article{arxiv.2402.18274,
title = {Ferroelectrically tunable topological phase transition in In$_2$Se$_3$ thin films},
author = {Zhiqiang Tian and Ziming Zhu and Jiang Zeng and Chao-Fei Liu and Yurong Yang and Anlian Pan and Mingxing Chen},
journal= {arXiv preprint arXiv:2402.18274},
year = {2024}
}