title: Parity-forbidden excitations of Sr(2)CuO(2)Cl(2) revealed by optical third-harmonic spectroscopy.
abstract: We present the first study of nonlinear optical third-harmonic generation (THG) in the strongly correlated charge-transfer insulator Sr(2)CuO(2)Cl(2). For fundamental excitation in the near infrared, the THG spectrum reveals a strongly resonant response for photon energies near 0.7 eV. Polarization analysis reveals this novel resonance to be only partially accounted for by three-photon excitation to the optical charge-transfer exciton, and indicates that an even-parity state at 2 eV, with a(1g) symmetry, participates in the third-harmonic susceptibility.
authors.affiliation: Department of Physics, University of California at Berkeley, Berkeley, CA 94720, USA.
authors.forename: A B
authors.initials: AB
authors.lastname: Schumacher
authors.forename: J S
authors.initials: JS
authors.lastname: Dodge
authors.forename: M A
authors.initials: MA
authors.lastname: Carnahan
authors.forename: R A
authors.initials: RA
authors.lastname: Kaindl
authors.forename: D S
authors.initials: DS
authors.lastname: Chemla
authors.forename: L L
authors.initials: LL
authors.lastname: Miller