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

TL;DR

This paper theoretically investigates the electronic structures and optical excitations in Moebius conjugated polymers, revealing how boundary conditions influence optical properties and polarization dependence, aiding in experimental detection.

Contribution

It introduces a theoretical model for Moebius conjugated polymers considering boundary conditions and exciton effects, highlighting the role of oligomers in observing boundary-induced effects.

Findings

Oligomers are more effective than polymers for observing boundary effects.

Optical absorption spectra depend on boundary conditions and polarization.

Polarization dependence can be used to detect Moebius boundary in conjugated polymers.

Abstract

Electronic structures and optical excitations in Moebius conjugated polymers are studied theoretically. Periodic and Moebius 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 Moebius boundary.