Plasmon Enhanced Raman Scattering Effect for an Atom near a Carbon Nanotube

Most of the applications of carbon nanotubes (CNs) to increase the Raman scattering signal have been to decorate them with metallic nanoparticles, in order to obtain the local electromagnetic field enhancement due to spatially confined plasmon modes of the nanoparticles, with CNs only used as a network to support the nanoparticles. Recently, the chemical Surface Enhanced Raman Scattering (SERS) effect with CNs alone was first reported [Andrada et al., Carbon 56, 235 (2013)], where molecules covalently bound to single wall CNs demonstrated the resonantly increased Raman signal that was even stronger than that of the CN itself. Here, the Quantum Electrodynamics theory of the resonance Raman scattering is developed [arXiv1407.5142, submitted] for a two-level dipole emitter, two-level system (TLS), coupled to a weakly-dispersive low-energy (~1−2 eV) interband plasmon resonance of a CN, to demonstrate that individual CNs are capable of providing the electromagnetic SERS effect as well. The theory applies to atomic type species such as atoms, ions, molecules, or semiconductor quantum dots that are physisorbed on the CN walls. The analytical expression derived for the Raman cross-section covers both weak and strong TLS–plasmon coupling, and shows dramatic enhancement in the strong coupling regime. The enhancement is due to the plasmon-induced near-fields that affect the TLS in a close proximity to the CN surface, given that the TLS transition energy is within the spectral band of ~0.43 eV of the corresponding CN interband plasmon resonance energy. This theoretical work provides a unified description of the near-field plasmon enhancement effects that will help establish new design concepts for future generation CN based nanophotonics platforms with varied characteristics pre-defined on-demand — due to extraordinary stability, flexibility and precise tunability of the electromagnetic properties of CNs by means of their diameter/chirality variation — for single molecule/atom/ion detection, precision spontaneous emission control, and optical manipulation.

This work is supported by DOE (DE-SC0007117).

ibondarev@nccu.edu