Exciton Ionization, Franz-Keldysh and Stark Effects in Carbon Nanotubes

TL;DR

This paper investigates how external electric fields influence the optical properties of carbon nanotubes, revealing strong Franz-Keldysh oscillations, Stark effects, and exciton ionization behaviors relevant for optoelectronic applications.

Contribution

It provides detailed theoretical predictions of exciton ionization, Franz-Keldysh oscillations, and Stark effects in carbon nanotubes under electric fields, including phonon-assisted dissociation mechanisms.

Findings

Strong Franz-Keldysh oscillations in absorption peaks

Quadratic Stark effect on excitons

Significant increase in Sommerfeld factor up to 2000%

Abstract

We calculate the optical properties of carbon nanotubes in an external static electric field directed along the tube axis. We predict strong Franz-Keldysh oscillations in the first and second band-to-band absorption peaks, quadratic Stark effect of the first two excitons, and the field dependence of the bound exciton ionization rate for a wide range of tube chiralities. We find that the phonon assisted mechanism dominates the dissociation rate in electro-optical devices due to the hot optical phonons. We predict a quadratic dependence of the Sommerfeld factor on the electric field and its increase up to 2000% at the critical field of the full exciton dissociation.