Ab initio simulations of excited carrier dynamics in carbon nanotubes

TL;DR

This study uses combined density functional and molecular dynamics simulations to explore how excited carriers in a carbon nanotube decay over time, revealing temperature-dependent electron-phonon interactions.

Contribution

It introduces a novel simulation approach integrating electronic and ionic dynamics to analyze excited carrier behavior in carbon nanotubes.

Findings

Carrier decay initially driven by electron-electron scattering

Excitation gap reduces by nearly half after 230 fs at room temperature

Electron-phonon coupling effects depend on initial ion velocities

Abstract

Combining time-dependent density functional calculations for electrons with molecular dynamics simulations for ions, we investigate the dynamics of excited carriers in a (3,3) carbon nanotube at different temperatures. Following an hv=6.8 eV photoexcitation, the carrier decay is initially dominated by efficient electron-electron scattering. At room temperature, the excitation gap is reduced to nearly half its initial value after ~230 fs, where coupling to phonons starts dominating the decay. We show that the onset point and damping rate in the phonon regime change with initial ion velocities, a manifestation of temperature dependent electron-phonon coupling.