ИСТИНА

The family of 2D layered III-VI transition-metal chalcogenides, including GaS, GaSe, GaTe, InS, InSe, InTe, and also Janus structures like GaSSe, exhibit exceptional nonlinear optical properties. The most energetically favorable crystal ordering for this family is AA layer stacking, which breaks central inversion symmetry for an arbitrary number of layers, resulting in non-zero off-diagonal elements of the χ (2) tensor for arbitrary thickness of the materials. Experimentally, the nonresonant second harmonic response of GaSe is the strongest among all the 2D layered crystals. In this talk we will discuss methods to increase the nonlinear response in III-VI transition-metal chalcogenides by material design, using first-principles method based on many-body GW theory and Bethe-Salpeter equation, thereby taking band gap renormalization and excitonic effects into account.