Exciton Optical Absorption in Self-Similar Aperiodic Lattices

TL;DR

This study investigates how self-similar aperiodic lattices like Thue-Morse and Fibonacci influence exciton optical absorption, revealing unique spectral features due to their order, and explains these features using a two-center problem approach.

Contribution

It introduces a microscopic approach to analyze exciton absorption in self-similar aperiodic lattices and explains spectral features through a two-center block model.

Findings

Aperiodic order causes distinct absorption spectral features.

Spectra differ significantly from random lattices with similar parameters.

Two-center problem explains the origin of absorption lines.

Abstract

Exciton optical absorption in self-similar aperiodic one-dimensional systems is considered, focusing our attention on Thue-Morse and Fibonacci lattices as canonical examples. The absorption line shape is evaluated by solving the microscopic equations of motion of the Frenkel-exciton problem on the lattice, in which on-site energies take on two values, according to the Thue-Morse or Fibonacci sequences. Results are compared to those obtained in random lattices with the same stechiometry and size. We find that aperiodic order causes the occurrence of well-defined characteristic features in the absorption spectra which clearly differ from the case of random systems, indicating a most peculiar exciton dynamics. We successfully explain the obtained spectra in terms of the two-center problem. This allows us to establish the origin of all the absorption lines by considering the self-similar aperiodic lattices as composed of two-center blocks, within the same spirit of the renormalization group ideas.