Electron-phonon coupling in metallic carbon nanotubes: Dispersionless electron propagation despite dissipation

TL;DR

This study demonstrates that metallic carbon nanotubes can support nearly dispersionless electron propagation over micron distances at room temperature, despite electron-phonon interactions causing dissipation and decoherence.

Contribution

The paper provides a detailed analysis using a Lindblad density-matrix approach, showing that electron wave packets in metallic SWNTs remain undispersed even with energy dissipation and decoherence effects.

Findings

Electron diffusion in metallic SWNTs is minimal and energy distribution independent.

The non-dispersive propagation is robust against variations in chemical potential.

High initial excitation energies do not significantly affect electron propagation.

Abstract

A recent study [Rosati, Dolcini, and Rossi, Appl. Phys. Lett. 106, 243101 (2015)] has predicted that, while in semiconducting single-walled carbon nanotubes (SWNTs) an electronic wave packet experiences the typical spatial diffusion of conventional materials, in metallic SWNTs its shape remains essentially unaltered up to micron distances at room temperature, even in the presence of the electron-phonon coupling. Here, by utilizing a Lindblad-based density-matrix approach enabling us to account for both dissipation and decoherence effects, we test such prediction by analyzing various aspects that were so far unexplored. In particular, accounting for initial nonequilibrium excitations, characterized by an excess energy $E_0$, and including both intra- and interband phonon scattering, we show that for realistically high values of $E_0$ the electronic diffusion is extremely small and nearly independent of its energetic distribution, in spite of a significant energy-dissipation and decoherence dynamics. Furthermore, we demonstrate that the effect is robust with respect to the variation of the chemical potential. Our results thus suggest that metallic SWNTs are a promising platform to realise quantum channels for the non-dispersive transmission of electronic wave packets.