Origin of electronic Raman scattering and the Fano resonance in metallic carbon nanotubes

TL;DR

This paper investigates the origin of Fano resonance in metallic carbon nanotubes, attributing it to interference between electronic and phonon spectra, and reveals asymmetric RBM spectra overlooked before.

Contribution

It demonstrates that second-order electron-electron interactions are key to the Fano resonance and uncovers asymmetric RBM spectra in metallic nanotubes.

Findings

Fano resonance arises from interference between electronic and phonon spectra.

Second-order q ≠ 0 electron-electron interactions are more relevant than first-order.

RBM spectra exhibit an asymmetric line shape previously overlooked.

Abstract

Fano resonance spectra for the G band in metallic carbon nanotubes are calculated as a function of laser excitation energy in which the origin of the resonance is given by an interference between the continuous electronic Raman spectra and the discrete phonon spectra. We found that the second-order scattering process of the non-zero q electron-electron interaction is more relevant to the continuous spectra rather than the q = 0 first-order process because the q = 0 direct Coulomb interaction vanishes due to the symmetry of the two sublattices of a nanotube. We also show that the RBM spectra of metallic carbon nanotubes have an asymmetric line shape which previously had been overlooked.