Electronic ferroelectricity in carbon based materials

TL;DR

This paper reviews the potential for electronic ferroelectricity in carbon-based materials, emphasizing conjugated polymers and graphene nano-ribbons, highlighting their high polarizability and unique soliton-based domain structures.

Contribution

It proposes the concept of electronic ferroelectricity in conjugated polymers and other carbon materials, emphasizing symmetry-driven design and soliton-based domain walls.

Findings

Electronic ferroelectricity can arise from electronic density redistribution.

Microscopic solitons act as nano-scale ferroelectric domain nuclei.

Potential applications in carbon-based ferroelectric devices.

Abstract

We review existing manifestations and prospects for ferroelectricity in electronically and optically active carbon-based materials. The focus point is the proposal for the electronic ferroelectricity in conjugated polymers from the family of substituted polyacetylenes. The attractive feature of synthetic organic ferroelectrics is a very high polarizability coming from redistribution of the electronic density, rather than from conventional displacements of ions. Next fortunate peculiarity is the symmetry determined predictable design of perspective materials. The macroscopic electric polarization follows ultimately from combination of two types of a microscopic symmetry breaking which are ubiquitous to qusi-1D electronic systems. The state supports anomalous quasi-particles - microscopic solitons, carrying non-integer electric charges, which here play the role of nano-scale nucleus of ferroelectric domain walls. Their spectroscopic features in optics can interfere with low-frequency ferroelectric repolarization providing new accesses and applications. In addition to already existing electronic ferroelectricity in organic crystals and donor-acceptor chains, we point to a class of conducting polymers and may be also to nano-ribbons of the graphene where such a state can be found. These proposals may lead to potential applications in modern intensive searches of carbon ferroelectrics.