Vertical Stress Induced Anomalous Spectral Shift of 13.17° Moire Superlattice in Twist Bilayer Graphene

The electronic states of the twist bilayer graphene (TBG) moire superlattice are usually regulated by the rotation angle, applied electric field, applied magnetic field, carrier concentration and applied stress, and thus exhibit novel physical properties. Squeezing, that is, applying vertical compressive stress to the graphene layers, has profound significance in regulating the photoelectric properties of the moire superlattice and constructing optical nanodevices. This paper presents the photoelectric properties of a TBG moire superlattice with a twist angle of 13.17 degrees and tunability under vertical stress. Interlayer distance decreases nonlinearly with compressive stress from 0 to 10 GPa, giving rise to weakened interlayer coupling compared to a Bernal-stacked graphene bilayer and an enhanced repulsive effect between the layers. The calculated Bloch wave functions show a strong dependence on stress. With the increase in stress, the band gaps of the system present a nonlinear increase, which induces and enhances the interlayer charge transfer and leads to the redshift of the absorption spectrum of the moire superlattice system. By analyzing the differences in the Bloch wave function and charge density differences, we explain the nature of the physical mechanism of photoelectric property change in a stress-regulated twist superlattice system. This study provides a theoretical basis for the identification of piezoelectric properties and the stress regulation of photoelectric devices based on TBG, and also provides a feasible method for regulating the performance of TBG.

Automated summary

This paper presents the photoelectric properties of a twist bilayer graphene (TBG) moire superlattice under vertical stress. It is found that the increase in stress leads to a nonlinear increase in the band gaps of the system, inducing and enhancing interlayer charge transfer and resulting in the redshift of the absorption spectrum. The physical mechanism of the photoelectric property change in the stress-regulated TBG system is explained by analyzing the differences in the Bloch wave function and charge density.