Emergent second-harmonic generation in van der Waals heterostructure of bilayer MoS2 and monolayer graphene

Mingwen Zhang; Nannan Han; Jiachen Zhang; Jing Wang; Xiaoqing Chen; Jianlin Zhao; Xuetao Gan

doi:10.1126/sciadv.adf4571

Emergent second-harmonic generation in van der Waals heterostructure of bilayer MoS₂ and monolayer graphene

Sci Adv. 2023 Mar 17;9(11):eadf4571. doi: 10.1126/sciadv.adf4571. Epub 2023 Mar 15.

Authors

Mingwen Zhang¹, Nannan Han², Jiachen Zhang¹, Jing Wang¹, Xiaoqing Chen¹, Jianlin Zhao¹, Xuetao Gan^{1

3}

Affiliations

¹ Key Laboratory of Light Field Manipulation and Information Acquisition, Ministry of Industry and Information Technology, and Shaanxi Key Laboratory of Optical Information Technology, School of Physical Science and Technology, Northwestern Polytechnical University, Xi'an 710129, China.
² Frontiers Science Center for Flexible Electronics, Xi'an Institute of Flexible Electronics (IFE), and Xi'an Institute of Biomedical Materials and Engineering, Northwestern Polytechnical University, Xi'an 710129, China.
³ School of Microelectronics, Northwestern Polytechnical University, Xi'an 710129, China.

Abstract

Van der Waals (vdW) stacking of two-dimensional (2D) materials to create artificial structures has enabled remarkable discoveries and novel properties in fundamental physics. Here, we report that vdW stacking of centrosymmetric 2D materials, e.g., bilayer MoS₂ (2LM) and monolayer graphene (1LG), could support remarkable second-harmonic generation (SHG). The required centrosymmetry breaking for second-order hyperpolarizability arises from the interlayer charge transfer between 2LM and 1LG and the imbalanced charge distribution in 2LM, which are verified by first-principles calculations, Raman spectroscopy, and polarization-resolved SHG. The strength of SHG from 2LM/1LG is of the same order of magnitude as that from the monolayer MoS₂, which is well recognized with strong second-order nonlinearity. The emergent SHG reveals that the interlayer charge transfer can effectively modify the symmetry and nonlinear optical properties of 2D heterostructures. It also indicates the great opportunity of SHG spectroscopy for characterizing interlayer coupling in vdW heterostructures.