title: Excitons in carbon nanotubes: an ab initio symmetry-based approach.
abstract: The optical absorption spectrum of the carbon (4,2) nanotube is computed using an ab initio many-body approach which takes into account excitonic effects. We develop a new method involving a local basis set which is symmetric with respect to the screw-symmetry of the tube. Such a method has the advantages of scaling faster than plane-wave methods and allowing for a precise determination of the symmetry character of the single-particle states, two-particle excitations, and selection rules. The binding energy of the lowest, optically active states is approximately 0.8 eV. The corresponding exciton wave functions are delocalized along the circumference of the tube and localized in the direction of the tube axis.
authors.affiliation: INFM National Center on NanoStructures and BioSystems at Surfaces (S3) and Dipartimento di Fisica, Università di Modena e Reggio Emilia, Via Campi 213/A, 41100 Modena, Italy.
authors.forename: Eric
authors.initials: E
authors.lastname: Chang
authors.forename: Giovanni
authors.initials: G
authors.lastname: Bussi
authors.forename: Alice
authors.initials: A
authors.lastname: Ruini
authors.forename: Elisa
authors.initials: E
authors.lastname: Molinari