G band Raman double resonance in twisted bilayer graphene: an evidence of band splitting and folding

TL;DR

This study investigates how stacking faults in twisted bilayer graphene cause band splitting and folding, affecting electronic and optical properties, and demonstrates that these effects enable G band Raman double resonance observable in experiments.

Contribution

It provides first-principles predictions and experimental evidence that stacking-induced band folding enables G band Raman double resonance in twisted bilayer graphene.

Findings

Band folding enables G band Raman double resonance.

Resonant energies depend on stacking geometry.

Experimental Raman observations confirm theoretical predictions.

Abstract

The stacking faults (deviates from Bernal) will break the translational symmetry of multilayer graphenes and modify their electronic and optical behaviors to the extent depending on the interlayer coupling strength. This paper addresses the stacking-induced band splitting and folding effect on the electronic band structure of twisted bilayer graphene. Based on the first-principles density functional theory study, we predict that the band folding effect of graphene layers may enable the G band Raman double resonance in the visible excitation range. Such prediction is confirmed experimentally with our Raman observation that the resonant energies of the resonant G mode are strongly dependent on the stacking geometry of graphene layers.