Layer-selective Optical Second-harmonic Generation Spectroscopy of a MoS<sub>2</sub>/WSe<sub>2</sub> Heterobilayer

The so-called C exciton resonance enhancement peak for heterostructures (HSs) of transition-metal dichalcogenides is indicative of a change in the band structure due to interlayer coupling. However, the superposition of the broad C exciton peaks from the two layers presents a significant challenge to the analysis of the alteration. The aim of this study was to gain insight into the electronic states of the C exciton region in each layer of a MoS2/WSe2 HS. To this end, we obtained second-harmonic generation (SHG) spectra of the HS by fixing the incident polarization angle to sequentially minimize the second-harmonic signals from the WSe2 and MoS2 layers. The resulting SHG spectra comprised signals from the MoS2 (former case) and WSe2 layers (latter case), demonstrating that the C exciton peak from each layer of the HS could be observed individually.