Variable Electron-Phonon Coupling in Isolated Metallic Carbon Nanotubes Observed by Raman Scattering

TL;DR

This study reveals that electron-phonon coupling in isolated metallic carbon nanotubes varies with their chiral structure and Fermi energy, affecting Raman spectral features, which has implications for nanotube electronic properties.

Contribution

It demonstrates variable electron-phonon coupling in metallic carbon nanotubes depending on chirality and Fermi level, observed through Raman scattering.

Findings

Peak width varies significantly with nanotube chirality.

Electrostatic gating reduces Raman peak widths.

Coupling strength depends on chiral index and Fermi energy.

Abstract

We report the existence of broad and weakly asymmetric features in the high-energy (G) Raman modes of freely suspended metallic carbon nanotubes of defined chiral index. A significant variation in peak width (from 12 cm-1 to 110 cm-1) is observed as a function of the nanotube's chiral structure. When the nanotubes are electrostatically gated, the peak widths decrease. The broadness of the Raman features is understood as the consequence of coupling of the phonon to electron-hole pairs, the strength of which varies with the nanotube chiral index and the position of the Fermi energy.