Ferroelectric instability of two-dimensional crystals

TL;DR

This paper derives a relation for dielectric permittivity in 2D crystals, revealing that strong electron interactions induce spontaneous polarization, leading to potential ferroelectric transitions with applications in electrodynamics and optics.

Contribution

It introduces a new relation for 2D crystals' dielectric properties and predicts ferroelectricity driven by electron interactions, contrasting with 3D materials.

Findings

Derivation of a dielectric relation for 2D crystals.

Prediction of spontaneous electric polarization in 2D materials.

Potential for ferroelectric transition in 2D systems.

Abstract

The macroscopic dielectric permittivity of dielectric crystals is related to the microscopic atomic polarizability of constituent atoms by the known Clausius-Mossotti relation obtained in the middle of 19th century. We derive a similar relation for recently discovered two-dimensional crystals (mono- and bilayer graphene, boron nitride, etc) and show that, in contrast to three-dimensional materials, much stronger electron-electron interaction in two dimensions leads to a spontaneous electric polarization of the ground state of two-dimensional crystals. The predicted ferroelectric transition may have interesting applications in electrodynamics and optics.