Perspectives for the Ferroelectricity in π-Conjugated Systems
Date : May 20, 2009 16:00 ~
Speaker : Prof. N. Kirova(University of Paris-Sud, Orsay, France)
Professor :
Location : 56동106호
Ferroelectricity is a demanded effect in fundamental and applied solid state physics. Till now, the ferroelectrics were known mostly as insulating materials of the inorganic world. In this talk, we discuss a feasibility of obtaining ferroelectric, and the same time electronically and optically active, carbon-based materials: conducting polymers and may be graphene nanoribbons.
Ferroelectricity related to the charge ordering was discovered in quasi-1D organic conducting crystals, and extended to some layered compounds. The microscopic picture for the ferroelectricity in π - conjugated systems is based on two coexisting symmetry lowering effects: dimerizations of bonds and of sites: one of them being build-in, another comes as a spontaneous symmetry breaking. The theory predicts an existence of solitons with non-integer variable charges, both with and without spin, which are the walls separating domains with opposite electric polarisation. Their physics will serve to relate transient ferroelectric processes and the visible-range optics. For graphene nanoribbons, the zigzag edges possess the build-in dimerization of sites for edge carbon atoms, while the spontaneous one may come from electron-phonon interactions.
Ferroelectricity related to the charge ordering was discovered in quasi-1D organic conducting crystals, and extended to some layered compounds. The microscopic picture for the ferroelectricity in π - conjugated systems is based on two coexisting symmetry lowering effects: dimerizations of bonds and of sites: one of them being build-in, another comes as a spontaneous symmetry breaking. The theory predicts an existence of solitons with non-integer variable charges, both with and without spin, which are the walls separating domains with opposite electric polarisation. Their physics will serve to relate transient ferroelectric processes and the visible-range optics. For graphene nanoribbons, the zigzag edges possess the build-in dimerization of sites for edge carbon atoms, while the spontaneous one may come from electron-phonon interactions.