Photonic properties of monolayer ZrS2, PtSe2 and ZrS2/PtSe2 van der Waals heterojunctions under shear strain: a first-principles study

Abstract This study employs first-principles calculations to systematically investigate the electronic and optical property evolution of single-layer ZrS 2 , PtSe 2 , and their ZrS 2 /PtSe 2 heterojunctions under shear strains in the x–y and y–x directions. Structural stability is verified through phonon spectra and binding energy analysis, with the configuration exhibiting the lowest binding energy selected for further analysis. The results show that the bandgap of single-layer ZrS 2 and PtSe 2 decreases by approximately 49% and 40%, respectively, under 6% shear strain in the x–y direction; the bandgap of the ZrS 2 /PtSe 2 heterojunction is significantly lower than that of the individual layers. Under 6% shear strain in the y–x direction, it exhibits metallic behavior, while under 6% strain in the x–y direction, the bandgap decreases by approximately 98% compared to the intrinsic value, indicating a strain-induced electronic structure phase transition. Additionally, the heterojunction maintains stable II-type band alignment, facilitating spatial separation of photogenerated carriers and further enhancing device efficiency. The heterojunction exhibits higher electrostatic constants in the x–y direction and corresponding strain sensitivity, demonstrating an anisotropic polarization response. Analysis of the imaginary part of the dielectric function and absorption spectra reveals multiple enhanced absorption peaks in the high-energy region, with the main peak absorption coefficient far exceeding that of the single-layer material. The red shift of the absorption peaks, complementary intensity, and enhanced reflection phenomenon highlights its excellent strain-induced tuning capability and optical anisotropy.