期刊
ADVANCED OPTICAL MATERIALS
卷 10, 期 12, 页码 -出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/adom.202200085
关键词
2D semiconductors; excitons; near-field optics; nonlinear optics; stacking order
资金
- Programmable Quantum Materials (Pro-QM), an Energy Frontier Research Center - U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES) [DE-SC0019443]
This study demonstrates near-field second harmonic generation (SHG) imaging of 2D semiconductors and heterostructures using a scattering-type nano-optical apparatus, achieving a spatial resolution down to 20 nm. Excitons in atomically thin transition metal dichalcogenides greatly enhance the near-field SHG efficiency. By correlating nonlinear and linear scattering-type nano-imaging, nanoscale variations of interlayer stacking order in bilayer WSe2 are resolved, revealing stacking-tuned excitonic light-matter interactions.
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, near-field SHG imaging of 2D semiconductors and heterostructures with the spatial resolution down to 20 nm is demonstrated using a scattering-type nano-optical apparatus. It is shown 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, nanoscale variations of interlayer stacking order in bilayer WSe2 are resolved, and the stacking-tuned excitonic light-matter interactions are revealed. This 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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