Intertube Excitonic Coupling in Nanotube Van der Waals Heterostructures

Strong intertube excitonic coupling is demonstrated in 1D van der Waals heterostructures by examining the ultrafast response of radial C/BN/MoS2 core/shell/skin nanotubes to femtosecond infrared light pulses. Remarkably, infrared excitation of excitons in the semiconducting carbon nanotubes (CNTs) creates a prominent excitonic response in the visible range from the MoS2 skin, even with infrared photons at energies well below the bandgap of MoS2. Via classical analogies and a quantum model of the light-matter interaction these findings are assigned to intertube excitonic correlations. Dipole-dipole Coulomb interactions in the coherent regime produce intertube biexcitons, which persist for tens of femtoseconds, while on longer timescales (>100 ps) hole tunneling-from the CNT core, through the BN tunnel barrier, to the MoS2 skin-creates intertube excitons. Charge transfer and dipole-dipole interactions thus play prominent roles on different timescales, and establish new possibilities for the multi-functional use of these new nanoscale coaxial cables.