Exciton Radiative Lifetimes and Their Temperature Dependence in Single-Walled Carbon Nanotubes

We have investigated the radiative lifetimes of excitons in single-walled carbon nanotubes (SWNTs) from simultaneous measurements of the photoluminescence (PL) lifetimes [1] and the PL quantum yields. A high-quality sample of PFO dispersed-SWNTs was used for the PL measurements. The evaluated radiative lifetimes were ${\sim5-15}$ ns for SWNTs with diameters ${\sim0.8-1.1}$ nm at room temperature. The radiative lifetimes increased with the tube diameter. The exciton spatial coherence volume (length) was of the order ${10} ^{2}$ nm along the tube axis, as deduced from the radiative lifetimes. Furthermore, we discuss the dynamics of bright and dark excitons [2] from the temperature dependence of the radiative lifetime (10 to 300 K).\\[3pt] [1] H. Hirori, K. Matsuda, Y. Miyauchi, S. Maruyama, and Y. Kanemitsu, Phys. Rev. Lett. ${\bf 97}$, 257401 (2006). \\[0pt] [2] R. Matsunaga, K. Matsuda, and Y. Kanemitsu, Phys. Rev. Lett. ${\bf 101}$, 147404 (2008).