Manipulation of nonlinear optical responses in layered ferroelectric niobium oxide dihalides

• Published in: Nature communications Vol. 14; no. 1; p. 5911
• Main Authors: Ye, Liangting, Zhou, Wenju, Huang, Dajian, Jiang, Xiao, Guo, Qiangbing, Cao, Xinyu, Yan, Shaohua, Wang, Xinyu, Jia, Donghan, Jiang, Dequan, Wang, Yonggang, Wu, Xiaoqiang, Zhang, Xiao, Li, Yang, Lei, Hechang, Gou, Huiyang, Huang, Bing
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group 22.09.2023; Nature Publishing Group UK; Nature Portfolio
• Subjects: Antiferroelectricity; Brillouin zones; External pressure; Ferroelectric materials; Nesting; Niobium; Niobium oxides; Nonlinear optics; Optics; Optoelectronic devices; Phase transitions; Photovoltaic effect; Photovoltaics; Polarized light; Second harmonic generation
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-023-41383-7

Abstract Realization of highly tunable second-order nonlinear optical responses, e.g., second-harmonic generation and bulk photovoltaic effect, is critical for developing modern optical and optoelectronic devices. Recently, the van der Waals niobium oxide dihalides are discovered to exhibit unusually large second-harmonic generation. However, the physical origin and possible tunability of nonlinear optical responses in these materials remain to be unclear. In this article, we reveal that the large second-harmonic generation in NbO X 2 ( X  = Cl, Br, and I) may be partially contributed by the large band nesting effect in different Brillouin zone. Interestingly, the NbOCl 2 can exhibit dramatically different strain-dependent bulk photovoltaic effect under different polarized light, originating from the light-polarization-dependent orbital transitions. Importantly, we achieve a reversible ferroelectric-to-antiferroelectric phase transition in NbOCl 2 and a reversible ferroelectric-to-paraelectric phase transition in NbOI 2 under a certain region of external pressure, accompanied by the greatly tunable nonlinear optical responses but with different microscopic mechanisms. Our study establishes the interesting external-field tunability of NbO X 2 for nonlinear optical device applications.