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arXiv · 2501.16741

Quantum Geometric Origin of Strain-Tunable Giant Second-Harmonic Generation in Bi$_2$O$_2$X (X=S, Se, Te)

Zhefeng Lou·Zhihao Gong·Ziye Zhu·Wenbin Li·Xiao Lin·Hua Wang
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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 Bi$_2$O$_2$X (X = S, Se, Te). The SHG susceptibilities of Bi$_2$O$_2$X 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 Bi$_2$O$_2$X. Intriguingly, in Bi$_2$O$_2$Te, 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.

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Zhefeng Lou, Zhihao Gong, Ziye Zhu, Wenbin Li, Xiao Lin, Hua Wang. 2025-01-28. Quantum Geometric Origin of Strain-Tunable Giant Second-Harmonic Generation in Bi$_2$O$_2$X (X=S, Se, Te). https://arxiv.org/abs/2501.16741

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