Substrate Doping Effect and Unusually Large Angle van Hove Singularity Evolution in Twisted Bi- and Multilayer...

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Graphene possesses exceptional electronic properties, making it suitable for advanced electronic applications.
• The electronic structure of multilayer graphene can be precisely controlled by introducing twist angles between layers.

Purpose of the Study:

• To systematically investigate the evolution of band structures and van Hove singularities (vHSs) in twisted bilayer and trilayer graphene.
• To explore the tunability of vHS binding energy with varying twist angles.

Main Methods:

• Angle-resolved photoemission spectroscopy (ARPES) with sub-micrometer spatial resolution.
• Fabrication and characterization of twisted bilayer and trilayer graphene samples with twist angles ranging from 5° to 31°.

Main Results:

• Direct observation of a doping effect in multilayer graphene systems.
• Formation and wide tunability (over 2 eV) of vHSs in bilayer graphene with twist angle.
• Observation of multiple vHSs at different binding energies in trilayer graphene.

Conclusions:

• Twisted multilayer graphene offers a versatile platform for engineering electronic band structures.
• The tunable vHSs provide a promising material basis for optoelectrical applications requiring broadband wavelength selectivity (IR to UV).
• Demonstrated potential in wavelength-selective photodetector applications.