title: The optical resonances in carbon nanotubes arise from excitons.
abstract: Optical transitions in carbon nanotubes are of central importance for nanotube characterization. They also provide insight into the nature of excited states in these one-dimensional systems. Recent work suggests that light absorption produces strongly correlated electron-hole states in the form of excitons. However, it has been difficult to rule out a simpler model in which resonances arise from the van Hove singularities associated with the one-dimensional band [corrected] structure of the nanotubes. Here, two-photon excitation spectroscopy bolsters the exciton picture. We found binding energies of approximately 400 millielectron volts for semiconducting single-walled nanotubes with 0.8-nanometer diameters. The results demonstrate the dominant role of many-body interactions in the excited-state properties of one-dimensional systems.
authors.affiliation: Departments of Physics and Electrical Engineering, Columbia University, 538 West 120th Street, New York, NY 10027, USA.
authors.forename: Feng
authors.initials: F
authors.lastname: Wang
authors.forename: Gordana
authors.initials: G
authors.lastname: Dukovic
authors.forename: Louis E
authors.initials: LE
authors.lastname: Brus
authors.forename: Tony F
authors.initials: TF
authors.lastname: Heinz