Carrier multiplication in carbon nanotubes studied by femtosecond pump-probe spectroscopy

Carbon nanotubes are one of the excellent materials for studying the many-body effects of excitons because of their unique band structures and large exciton binding energies. We studied exciton population dynamics in single-walled carbon nanotubes using pump-probe transient absorption measurements. The temporal profiles of the transient absorption signals depend on the excitation intensity and excitation photon energy. We observe carrier multiplication in carbon nanotubes at room temperature, when the excitation photon energy exceeds the third subband exciton energy. (c) 2008 American Institute of Physics.