[2P01-53] Poster Presentation

[2P47] Optical second harmonic spectroscopy of few-layer MoS₂ and WS₂ in the C exciton region

*Yasuyuki Hirata¹, Shinya Ohno², Takahiro Suzuki¹, Yoshihiro Miyauchi¹ (1. Department of Applied Physics, National Defense Academy of Japan, 2. Department of Physics, Faculty of Engineering, Yokohama National University)

Second harmonic generation (SHG) spectra of monolayer (ML-) and few-layer (FL-) MoS₂, monolayer (ML-) and few-layer (FL-) WS₂ are measured in the two-photon energy range from 2.4 eV to 3.2 eV. The spectra are resolved into two components, C1 and C2. The peak energy of the low-energy component C1 red-shifts as the number of layers increases from ML to FL for both MoS₂ and WS₂, indicating that the C1 component originates from interband transitions in a ring-shaped region with bands nesting around the Γ point. On the other hand, for the high-energy C2 component, the change in peak energy with the number of layers from ML to FL is negligible in both cases of MoS₂ and WS₂. This suggests that the C2 component is different from the C exciton in the linear optical spectrum, and it originates from excitation in a region where the band structure is less modified by interlayer coupling, revealing the existence of transitions to hidden states which is specific to the nonlinear optical spectrum.