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arXiv · 2111.06955

Nanoscale Optical Imaging of 2D Semiconductor Stacking Orders by Exciton-Enhanced Second Harmonic Generation

Kaiyuan Yao·Shuai Zhang·Emanuil Yanev·Kathleen McCreary·Hsun-Jen Chuang·Matthew R. Rosenberger·Thomas Darlington·Andrey Krayev·Berend T. Jonker·James C. Hone·D. N. Basov·P. James Schuck
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Abstract

Second harmonic generation (SHG) is a nonlinear optical response arising exclusively from broken inversion symmetry in the electric-dipole limit. Recently, SHG has attracted widespread interest as a versatile and noninvasive tool for characterization of crystal symmetry and emerging ferroic or topological orders in quantum materials. However, conventional far-field optics is unable to probe local symmetry at the deep subwavelength scale. Here, we demonstrate near-field SHG imaging of 2D semiconductors and heterostructures with the spatial resolution down to 20 nm using a scattering-type nano-optical apparatus. We show that near-field SHG efficiency is greatly enhanced by excitons in atomically thin transition metal dichalcogenides. Furthermore, by correlating nonlinear and linear scattering-type nano-imaging, we resolve nanoscale variations of interlayer stacking order in bilayer WSe2, and reveal the stacking-tuned excitonic light-matter-interactions. Our work demonstrates nonlinear optical interrogation of crystal symmetry and structure-property relationships at the nanometer length scales relevant to emerging properties in quantum materials.

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Kaiyuan Yao, Shuai Zhang, Emanuil Yanev, Kathleen McCreary, Hsun-Jen Chuang, Matthew R. Rosenberger, Thomas Darlington, Andrey Krayev, Berend T. Jonker, James C. Hone, D. N. Basov, P. James Schuck. 2021-11-12. Nanoscale Optical Imaging of 2D Semiconductor Stacking Orders by Exciton-Enhanced Second Harmonic Generation. https://arxiv.org/abs/2111.06955

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