Excitonic Rayleigh scattering spectra of metallic single-walled carbon nanotubes

Abstract

We have performed microscopic calculations of the Rayleigh scattering cross section for arbitrary metallic single-walled carbon nanotubes. The focus of our investigations lies on excitonic effects and their influence on the characteristic features in a Rayleigh scattering spectrum. Our approach is based on density matrix theory including tight-binding energies, the carrier-light coupling as well as the carrier-carrier interaction. Due to the refractive index contribution to the scattering cross section, we observe characteristic features in Rayleigh spectra, such as a strong deviation from the Lorentz peak shape and the larger oscillator strength of the lower-lying transition M − ii in the double-peaked structure, independently of the chiral angle and the diameter of the investigated nanotubes. We observe excitonic binding energies in the range of 60 − 80 meV for metallic nanotubes with diameters of 1.5 − 2.5 nm. The overlap of the excitonic transition with the close-by continuum has a significant influence on the peak shape and a minor influence on the peak intensity ratios. The presented results are in good agreement with recent experimental data.

True-color real-time imaging and spectroscopy of carbon nanotubes on substrates using enhanced Rayleigh scattering

“…Three years later, a supercontinuum (SC) white laser was employed to illuminate individual SWCNTs, which generated more distinct resonance Rayleigh scattering peaks [3]. Though excitonic in nature [4][5][6][7], the resonance peaks are related to the van Hove singularities (vHs) in the electron density of states, thus enabling chirality assignment of SWCNTs [8]. These resonance Rayleigh scattering peaks in the visible region imply that the SWCNTs should appear colored.…”

Ultrafast luminescence kinetics of metallic single-walled carbon nanotubes: Possible evidence for excitonic luminescence

“…5,6) have probed 1D excitons with large binding energies (∼300-400 meV) and enhancement of the oscillator strength in hydrogenlike Rydberg states. Theoretical studies on metallic SWNTs (M-SWNTs), such as on (3,3), (10,10), and (12,0) nanotubes, predict the formation of excitons with binding energies of ∼50-100 meV. 2,3 Experimentally, a few groups have reported the signature of exciton formation from absorption, 7 reflection, 8 and Rayleigh scattering measurements.…”

Excitonic signatures in the optical response of single‐wall carbon nanotubes

“…The question of excitonic excitations in metallic materials is very peculiar in 1D systems since the reduced screening of Coulomb interactions can lead to bound electron-hole pairs even in the presence of free carriers [37][38][39]. This has been observed experimentally in the case of metallic nanotubes by means of absorption spectroscopy [40] and Raman spectroscopy [41] for the lowest inter-sub-band transition M 11 .…”