Quantum Geometric Origin of Strain-Tunable Giant Second-Harmonic Generation in Bi$_2$O$_2$X (X=S, Se, Te)
Abstract
Two-dimensional (2D) materials with giant nonlinear optical (NLO) responses are essential for the development of advanced on-chip NLO devices. Using first-principles calculations, we predict a remarkable strain-induced enhancement of second-harmonic generation (SHG) in the high-performance 2D semiconductors BiOX (X = S, Se, Te). The SHG susceptibilities of BiOX under strain are on the order of 1~nm/V, rivalling the highest values reported among 2D materials. This giant SHG response originates from gauge-invariant geometric quantities, including the quantum metric, shift vector, and triple phase product. The strain also induces a bandgap variation in BiOX. Intriguingly, in BiOTe, strain-induced bandgap tuning drives a transition from a semiconductor to a half-metal, and ultimately to a polar metal. Our findings present a unique platform that combines strain-tunable bandgap engineering with exceptional NLO properties, while also highlighting the crucial role of quantum geometry in enhancing SHG.
Cite
@article{arxiv.2501.16741,
title = {Quantum Geometric Origin of Strain-Tunable Giant Second-Harmonic Generation in Bi$_2$O$_2$X (X=S, Se, Te)},
author = {Zhefeng Lou and Zhihao Gong and Ziye Zhu and Wenbin Li and Xiao Lin and Hua Wang},
journal= {arXiv preprint arXiv:2501.16741},
year = {2025}
}
Comments
8 pages, 4 figures