Optical absorption from solvation-induced polarons on nanotubes

TL;DR

This paper investigates the optical absorption characteristics of polarons formed by excess charges in 1D semiconductor nanotubes immersed in polar solvents, highlighting a dominant transition and the impact of thermal broadening.

Contribution

It introduces a simplified model to analyze optical absorption from solvation-induced polarons in nanotubes, emphasizing the transition to the second electronic level and thermal effects.

Findings

90% of absorption strength is in the transition to the second electronic level

Transition energy exceeds polaron binding energy

Thermal fluctuations cause significant broadening of the absorption feature

Abstract

When an excess charge carrier is added to a one-dimensional (1D) semiconductor immersed in a polar solvent, the carrier can undergo self-localization into a large-radius adiabatic polaron. We explore the local optical absorption from the ground state of 1D polarons using a simplified theoretical model for small-diameter tubular structures. It is found that about 90% of the absorption strength is contained in the transition to the second lowest-energy localized electronic level formed in the polarization potential well, with the equilibrium transition energy larger than the binding energy of the polaron. Thermal fluctuations, however, cause a very substantial -- an order of magnitude larger than the thermal energy -- broadening of the transition. The resulting broad absorption feature may serve as a signature for the optical detection of solvated charge carriers.