Enhancing Resonant Second-Harmonic Generation in Bilayer WSe2 by Layer-Dependent Exciton-Polaron Effect

IF 9.6 1区材料科学 Q1 CHEMISTRY, MULTIDISCIPLINARY

Nano Letters Pub Date : 2024-11-11 DOI:10.1021/acs.nanolett.4c04544

Soonyoung Cha, Tianyi Ouyang, Takashi Taniguchi, Kenji Watanabe, Nathaniel M. Gabor, Chun Hung Lui

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Abstract

Two-dimensional (2D) materials serve as exceptional platforms for controlled second-harmonic generation (SHG). Current approaches to SHG control often depend on nonresonant conditions or symmetry breaking via single-gate control. Here, we employ dual-gate bilayer WSe₂ to demonstrate an SHG enhancement concept that leverages strong exciton resonance and a layer-dependent exciton-polaron effect. By selectively localizing injected holes within one layer, we induce exciton-polaron states in the hole-filled layer while maintaining normal exciton states in the charge-neutral layer. The distinct resonant conditions of these layers effectively break interlayer inversion symmetry, thereby promoting resonant SHG. This method achieves a remarkable 40-fold enhancement of SHG at minimal electric field, equivalent to conditions near the dielectric-breakdown threshold but using only ∼3% of the critical breakdown field. Our results highlight SHG sensitivity to carrier density and type, offering a new tool for manipulating SHG and probing quantum states in 2D excitonic systems.

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通过层依赖性激子-极子效应增强双层 WSe2 中的共振二次谐波生成

二维（2D）材料是控制二次谐波发生（SHG）的绝佳平台。目前的 SHG 控制方法通常依赖于非共振条件或通过单门控制打破对称性。在这里，我们采用双栅双层 WSe2 来展示一种利用强激子共振和层依赖性激子-极子效应的 SHG 增强概念。通过选择性地将注入的空穴定位在一层中，我们在充满空穴的层中诱导出激子-极子态，同时在电荷中性层中保持正常的激子态。这些层的不同共振条件有效地打破了层间反转对称性，从而促进了共振 SHG。这种方法在最小电场条件下实现了 40 倍的 SHG 增强，相当于介质击穿阈值附近的条件，但只使用了临界击穿场的∼3%。我们的研究结果突显了 SHG 对载流子密度和类型的敏感性，为操纵 SHG 和探测二维激子系统中的量子态提供了一种新工具。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Nano Letters 工程技术-材料科学：综合

CiteScore

16.80

自引率

2.80%

发文量

1182

审稿时长

1.4 months

期刊介绍： Nano Letters serves as a dynamic platform for promptly disseminating original results in fundamental, applied, and emerging research across all facets of nanoscience and nanotechnology. A pivotal criterion for inclusion within Nano Letters is the convergence of at least two different areas or disciplines, ensuring a rich interdisciplinary scope. The journal is dedicated to fostering exploration in diverse areas, including: - Experimental and theoretical findings on physical, chemical, and biological phenomena at the nanoscale - Synthesis, characterization, and processing of organic, inorganic, polymer, and hybrid nanomaterials through physical, chemical, and biological methodologies - Modeling and simulation of synthetic, assembly, and interaction processes - Realization of integrated nanostructures and nano-engineered devices exhibiting advanced performance - Applications of nanoscale materials in living and environmental systems Nano Letters is committed to advancing and showcasing groundbreaking research that intersects various domains, fostering innovation and collaboration in the ever-evolving field of nanoscience and nanotechnology.