Photoluminescence of metallic single-walled carbon nanotubes: Role of interband and intraband transitions

The photoluminescence (PL) properties of metallic single-walled carbon nanotubes were investigated. Steady-state measurements showed interband excitonic PL in the first hyperbolic dispersion region. The decay kinetics of this interband excitonic PL was observed by femtosecond time-resolved measurements, which also showed the occurrence of intraband PL in the linear dispersion region. The decay time constant of interband excitonic PL is approximately 40 fs, while that of intraband PL is slower at the lower photon energy. This study demonstrates the role of interband and intraband transitions in the PL of a one-dimensional metal.