Effect of periodic potential on exciton states in semiconductor carbon nanotubes

TL;DR

This paper presents a theoretical study of how a surface acoustic wave-induced periodic potential affects exciton states in semiconductor carbon nanotubes, revealing band splitting, exciton energy shifts, and photoluminescence changes.

Contribution

It introduces a formalism to analyze exciton behavior in SWCNTs under periodic potentials, including Floquet band formation and optical transition modifications.

Findings

Floquet sub-bands caused by SAW potential.

Reduction of exciton oscillator strength and photoluminescence quenching.

Red shift of exciton energy and decreased binding energy.

Abstract

We develop a theoretical background to treat exciton states of semiconductor single-walled carbon nanotubes (SWCNTs) in presence of a periodic potential induced by the surface acoustic wave (SAW) propagating along semiconducting SWCNT. The formalism naturally accounts for the electronic bands splitting into the Floquet sub-bands brought about by the Bragg scattering on the SAW potential. Optically induced transitions within the Floquet states and formation of correlated electron-hole pairs, i.e., exciton states, are examined numerically. We discuss dynamical formation of new van Hove singularities within electron-hole continuum and associated reduction of the exciton oscillator strengths and its effect on the photoluminescence quenching in presence of the SAW. We argue that SAW induced dynamical gaps in the single particle dispersion leads to redistribution of the oscillator strength from excitons to the Floquet edge states. The simulations also confirm exciton energy Stark red shift as well as reduction in the binding energy. Comparison of our results with previous theoretical and experimental studies is provided.