Electronic Properties of Topological Materials: Optical Excitations in Möbius Conjugated Polymers

Abstract

Electronic structures and optical excitations in Möbius conjugated polymers are studied theoretically. Periodic and Möbius boundary conditions are applied to the tight binding model of poly(para-phenylene), taking exciton effects into account. We discuss that oligomers with a few structural units are more effective than polymers for observations of effects of discrete wave numbers that are shifted by the change in boundary condition. Next, calculations of optical absorption spectra are reported. Certain components of optical absorption for an electric field perpendicular to the polymer axis mix with absorption spectra for an electric field parallel to the polymer axis. Therefore, the polarization dependences of an electric field of light enable us to detect whether conjugated polymers have the Möbius boundary.