Critical curvature localization in graphene. I. Quantum-flexoelectricity effect

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Multi-layer graphene exhibits complex mechanical behaviors under deformation.
• Understanding curvature localization is crucial for predicting material properties and applications.
• The interplay between mechanical strain and electric polarization in 2D materials is an active research area.

Purpose of the Study:

• To report the discovery of a novel curvature-localizing buckling mode in multi-layer graphene.
• To investigate the mechanism behind shallow-kink corrugation formation.
• To explore the role of quantum flexoelectricity in curvature and polarization localization.

Main Methods:

• Density Functional Theory (DFT) analysis to model the buckling mode and its configuration.
• Development of an effective-locality model for electromechanics.
• Comparison with purely mechanical models of sandwich structures.

Main Results:

• Discovery of a subcritical buckling mode producing shallow-kink corrugation with a ~2 nm wide boundary layer.
• DFT and electromechanical models show curvature and electric-charge polarization coupling (quantum flexoelectricity).
• Curvature and polarization are focused within a ~0.86 nm band, exhibiting oscillating decay and lowered potential energy due to dipole-dipole interactions.

Conclusions:

• Quantum flexoelectricity drives the emergence of a highly localized boundary layer for curvature and polarization in multi-layer graphene.
• The predicted peak polarization density (~0.12 e-/nm-1 for 3° tilt) is controllable via macroscopic deformation.
• This phenomenon holds promise for selective graphene-surface functionalization and novel electronic applications.