Physical mechanism on the linear spectrum and nonlinear spectrum in a twist bilayer graphdiyne nanodisk

The one-photon absorption properties (OPA), two-photon absorption properties (TPA), electronic circular dichroism (ECD) spectra and partial DOS (PDOS) of a twist bilayer graphdiyne nanodisk (TwBLGDY-ND) were investigated by using a variety of quantum chemistry and wave function analyses. The physical mechanism of the twist bilayer graphdiyne nanodisk (TwBLGDY) with optical properties regulated by twisting angles was revealed. The results show that the twist angle makes the TwBLGDY form a moire superlattice structure, and electron excitation mainly occurs in the first ring of the moire superlattice structure. The contribution of atomic orbitals in these fragments to transition dipole moments is greater and electronic transitions are more likely to occur. When the twist angle increases from 0 & DEG; to 15 & DEG;, the absorption spectrum of the system is red shifted, which is mainly due to the enhancement of electron excitation characteristics. When the twist angle increases from 15 & DEG; to 27.5 & DEG;, the absorption spectrum of the system is blue shifted, due to the enhanced charge transfer within the layer. On the other hand, the twist angle can regulate the TPA absorption cross section of the system to enhance the intensity of the absorption spectrum. The twist angle can also regulate chirality by adjusting the spatial distribution of electric dipole transition and magnetic dipole transition. This study can provide theoretical guidance for constructing chiral optical devices based on the TwBLGDY structure.

Automated summary

The optical properties of a twist bilayer graphdiyne nanodisk were studied using quantum chemistry and wave function analyses. The twist angle was found to regulate the absorption spectrum, with a red shift observed at lower twist angles and a blue shift at higher twist angles. The twist angle also affected the two-photon absorption and chirality of the system. This study provides theoretical guidance for constructing chiral optical devices based on twist bilayer graphdiyne structures.