Electronic Raman Scattering in Twistronic Few-Layer Graphene

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Graphene's electronic properties are highly sensitive to its stacking order and interlayer coupling.
• Twisted bilayer graphene and related structures exhibit unique electronic band structures due to moiré potentials.
• Raman spectroscopy is a powerful, non-destructive technique for probing vibrational and electronic properties of materials.

Purpose of the Study:

• To investigate the electronic contribution to Raman scattering in twisted few-layer graphene (2- to 4-layer).
• To identify and characterize spectral features arising from van Hove singularities in moiré minibands.
• To establish Raman spectroscopy as a method for non-invasively determining the twist angle in these systems.

Main Methods:

• Theoretical study of electronic band structures in twisted few-layer graphene.
• Calculation of electronic contributions to Raman scattering spectra.
• Analysis of spectral features related to van Hove singularities and band folding.

Main Results:

• Two distinct peaks were observed in the Raman spectra, attributed to van Hove singularities.
• One peak originates from direct hybridization of Dirac states, the other from moiré superlattice band folding.
• The positions of these peaks show a strong dependence on the twist angle between layers.

Conclusions:

• The observed Raman peaks provide a direct signature of moiré minibands in twisted few-layer graphene.
• Raman spectroscopy can be effectively utilized for non-invasive characterization of twist angles.
• This method is applicable even in encapsulated graphene structures, such as those with hexagonal boron nitride (hBN).