Mixed-Stacking Few-Layer Graphene as an Elemental Weak Ferroelectric Material

Area of Science:

• Solid-state physics
• Materials science
• Condensed matter physics

Background:

• Ferroelectricity, the spontaneous formation of electric polarization, is a well-established phenomenon in ionic compounds and complex materials.
• Elemental solids have not traditionally been associated with ferroelectric properties.

Purpose of the Study:

• To investigate the potential for ferroelectricity in elemental solids, specifically few-layer graphenes.
• To identify specific graphene structures exhibiting switchable electric polarization.

Main Methods:

• Theoretical investigation of few-layer graphene structures.
• Analysis of mixed-stacking tetralayers and rhombohedral graphitic films (5-9 layers).
• Examination of marginally twisted few-layer graphene flakes.

Main Results:

• Few-layer graphenes can host equilibrium out-of-plane electric polarization.
• This polarization is switchable by sliding the constituent graphene sheets.
• Specific structures like mixed-stacking tetralayers, thicker rhombohedral films with twin boundaries, and twisted few-layer flakes exhibit this effect.

Conclusions:

• Elemental few-layer graphenes can exhibit ferroelectric properties, challenging traditional understanding.
• Switchable electric polarization in graphene opens possibilities for novel electronic applications.
• Lattice reconstruction in twisted graphene can lead to mesoscale domains of alternating polarization.