Theoretical investigation on electronic properties of topological materials: Optical excitations in Moebius conjugated polymers

TL;DR

This paper theoretically investigates the electronic structures and optical excitations of Moebius conjugated polymers, highlighting how boundary conditions influence optical properties and polarization dependence.

Contribution

It introduces a theoretical model for Moebius conjugated polymers, analyzing boundary effects and optical spectra, which is novel in understanding their unique optical properties.

Findings

Oligomers are more effective than polymers for measuring boundary effects.

Optical absorption spectra are affected by boundary conditions and polarization.

Polarization dependence can reveal the presence of Moebius boundary.

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 into account of the exciton effects by long-range Coulomb interactions. We first discuss that oligomers with a few structural units are more effective than polymers, in order to measure effects of discrete wave numbers which are shift by the Moebius boundary from those of the periodic boundary. Next, calculations of the optical absorption spectra are reported. Certain components of the optical absorption for the electric field perpendicular to the polymer axis mix with the absorption spectra for the electric filed parallel with the polymer axis. Therefore, the polarization dependences of electric field of light can detect whether conjugated polymers have the Moebius boundary or not.