Topological interfacial states at phase boundaries in two-dimensional ferroelectric bismuth

W Luo and Y Zhong and HY Yu and MT Xie and YW Chen and H Xiang and L Bellaiche, PHYSICAL REVIEW B, 111, 075407 (2025).

DOI: 10.1103/PhysRevB.111.075407

Using machine learning potential, we explore different types of domain walls in the recently unveiled single-element ferroelectric, the bismuth monolayer Gou et al., Nature (London) 617, 67 (2023). Remarkably, our investigation reveals that the charged domain-wall configuration exhibits lower energy compared to the uncharged domain-wall structure. Using the machine learning Hamiltonian, we directly calculate the band structures for large domain-wall systems and demonstrate that the experimentally discovered tail-to-tail domain wall preserves topological interfacial states, which arise from the change in the Z(2) topological number between the ferroelectric and paraelectric phases. Our study suggests that domain walls in two-dimensional bismuth hold potential as a promising platform for the development of ferroelectric domain-wall devices.

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