Fano resonances in Raman response of carbon nanotube bundles as signature of interacting excitons

Electronic interactions in low-dimensional nanomaterial heterostructures can lead to novel optical response arising from exciton delocalization over the constituent materials. Similar phenomena have been suggested to arise between closely interacting semiconducting single wall carbon nanotubes (SWCNTs) of identical structure. While not yet probed in detail, such behavior in SWCNTs has potential to open a path to new exciton physics, impact exciton transport mechanisms in SWCNT networks, and place SWCNTs as one-dimensional models for such behaviors in systems of higher dimensionality. Motivated by experimental studies on high purity bundles of (6,5) SWCNTs, we develop a scattering model for interacting intertube and intratube excitons in SWCNT bundles. Based on this model, the bundle Raman response is examined and the Raman excitation spectra are modeled. Our analysis shows that the scattering of bright intratube exciton by dark intertube one results in a sharp anomalous spectral feature identified as the Fano resonance. Furthermore, the universality of the model suggests that similar Raman excitation profile features may be observed for interlayer exciton resonances in 2D multilayered systems.