Experimental Observation of ABCB Stacked Tetralayer Graphene

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Tetralayer graphene theoretically possesses three stacking sequences: rhombohedral (ABCA), Bernal (ABAB), and the unobserved ABCB.
• The ABCB stacking is theoretically predicted to have unique electronic properties, including an intrinsic bandgap and flat bands.

Purpose of the Study:

• To experimentally identify and characterize domains of ABCB stacked tetralayer graphene.
• To differentiate between the three possible stacking sequences in tetralayer graphene.

Main Methods:

• Utilized scattering-type scanning near-field optical microscopy (s-SNOM) and confocal Raman microscopy.
• Employed amplitude and phase-resolved near-field nanospectroscopy to analyze optical conductivity between 0.28 and 0.56 eV.
• Normalized adjacent graphene flakes to enhance experimental accuracy and comparison with theoretical predictions.

Main Results:

• Successfully identified and characterized domains of ABCB stacked tetralayer graphene.
• Demonstrated that near-field spectroscopy of interband transitions can semiquantitatively distinguish between the three stacking sequences.
• Achieved good agreement between experimental results and theoretical predictions for optical conductivity.

Conclusions:

• Established near-field spectroscopy as a viable tool for recognizing ABCB domains in tetralayer graphene.
• The identification of ABCB stacking provides a foundation for investigating its unique correlation physics.
• This work advances the understanding of stacking-dependent properties in multilayer graphene systems.