Exciton energy spectra in polyyne chains

TL;DR

This paper estimates excitonic transition energies in polyyne chains, revealing how their fine structure is influenced by inter-chain interactions and charge effects, providing insights into their optical properties.

Contribution

It introduces a variational method to calculate exciton energies in complex quasi-one-dimensional carbon systems, considering inter-chain and charge effects.

Findings

Exciton energy scales are governed by inter-chain hopping and charge splitting.

The characteristic energies are an order of magnitude lower than the exciton binding energy.

The study explains the fine structure observed in photoluminescence spectra.

Abstract

Recently, we have experimentally observed signatures of sharp exciton peaks in the photoluminescence spectra of bundles of monoatomic carbon chains stabilized by gold nanoparticles and deposited on a glass substrate. Here, we estimate the characteristic energies of excitonic transitions in this complex quasi-one-dimensional nano-system with use of the variational method. We show that the characteristic energy scale for the experimentally observed excitonic fine structure is governed by the interplay between the hopping energy in a Van der Waals quasicrystal formed by parallel carbon chains, the neutral-charged exciton splitting and the positive-negative trion splitting. These three characteristic energies are an order of magnitude lower than the direct exciton binding energy.