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Gou J, Bai H, Zhang X, Huang YL, Duan S, Ariando A, Yang SA, Chen L, Lu Y, Wee ATS. Two-dimensional ferroelectricity in a single-element bismuth monolayer. Nature 2023; 617:67-72. [PMID: 37020017 PMCID: PMC10156600 DOI: 10.1038/s41586-023-05848-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Accepted: 02/15/2023] [Indexed: 04/07/2023]
Abstract
Ferroelectric materials are fascinating for their non-volatile switchable electric polarizations induced by the spontaneous inversion-symmetry breaking. However, in all of the conventional ferroelectric compounds, at least two constituent ions are required to support the polarization switching1,2. Here, we report the observation of a single-element ferroelectric state in a black phosphorus-like bismuth layer3, in which the ordered charge transfer and the regular atom distortion between sublattices happen simultaneously. Instead of a homogenous orbital configuration that ordinarily occurs in elementary substances, we found the Bi atoms in a black phosphorous-like Bi monolayer maintain a weak and anisotropic sp orbital hybridization, giving rise to the inversion-symmetry-broken buckled structure accompanied with charge redistribution in the unit cell. As a result, the in-plane electric polarization emerges in the Bi monolayer. Using the in-plane electric field produced by scanning probe microscopy, ferroelectric switching is further visualized experimentally. Owing to the conjugative locking between the charge transfer and atom displacement, we also observe the anomalous electric potential profile at the 180° tail-to-tail domain wall induced by competition between the electronic structure and electric polarization. This emergent single-element ferroelectricity broadens the mechanism of ferroelectrics and may enrich the applications of ferroelectronics in the future.
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Affiliation(s)
- Jian Gou
- Department of Physics, National University of Singapore, Singapore, Singapore.
| | - Hua Bai
- Zhejiang Province Key Laboratory of Quantum Technology and Device, School of Physics, State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, China
- Department of Physics, Faculty of Science, Kunming University of Science and Technology, Kunming, China
| | - Xuanlin Zhang
- Zhejiang Province Key Laboratory of Quantum Technology and Device, School of Physics, State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, China
| | - Yu Li Huang
- Joint School of National University of Singapore and Tianjin University, International Campus of Tianjin University, Fuzhou, China
| | - Sisheng Duan
- Department of Physics, National University of Singapore, Singapore, Singapore
| | - A Ariando
- Department of Physics, National University of Singapore, Singapore, Singapore
| | - Shengyuan A Yang
- Research Laboratory for Quantum Materials, Singapore University of Technology and Design, Singapore, Singapore
| | - Lan Chen
- Institute of Physics, Chinese Academy of Sciences, Beijing, China.
- School of Physics, University of Chinese Academy of Sciences, Beijing, China.
| | - Yunhao Lu
- Zhejiang Province Key Laboratory of Quantum Technology and Device, School of Physics, State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, China.
| | - Andrew Thye Shen Wee
- Department of Physics, National University of Singapore, Singapore, Singapore.
- Centre for Advanced 2D Materials (CA2DM) and Graphene Research Centre (GRC), National University of Singapore, Singapore, Singapore.
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