Parity-forbidden excitations of Sr(2)CuO(2)Cl(2) revealed by optical third-harmonic spectroscopy.
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.
Schumacher
A B
AB
Department of Physics, University of California at Berkeley, Berkeley, CA 94720, USA.
Dodge
J S
JS
Carnahan
M A
MA
Kaindl
R A
RA
Chemla
D S
DS
Miller
L L
LL