Parity-Forbidden Excitations of <span class="aps-inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>Sr</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow><mrow><msub><mrow><mi>CuO</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow><mrow><msub><mrow><mi>Cl</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></math></span> Revealed by Optical Third-Harmonic Spectroscopy

A. B. Schumacher; J. S. Dodge; M. A. Carnahan; R. A. Kaindl; D. S. Chemla; L. L. Miller

doi:10.1103/PhysRevLett.87.127006

Parity-Forbidden Excitations of ${Sr}_{2} {CuO}_{2} {Cl}_{2}$ Revealed by Optical Third-Harmonic Spectroscopy

A. B. Schumacher, J. S. Dodge, M. A. Carnahan, R. A. Kaindl, D. S. Chemla, and L. L. Miller

Phys. Rev. Lett. 87, 127006 – Published 31 August 2001

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 $a_{1 g}$ symmetry, participates in the third-harmonic susceptibility.

Received 9 March 2001

DOI:https://doi.org/10.1103/PhysRevLett.87.127006

Authors & Affiliations

A. B. Schumacher^*, J. S. Dodge^†, M. A. Carnahan, R. A. Kaindl, and D. S. Chemla

Department of Physics, University of California at Berkeley, Berkeley, California 94720
and Materials Sciences Division, E. O. Lawrence Berkeley National Laboratory, Berkeley, California 94720

L. L. Miller

Ames Laboratory and Department of Physics, Iowa State University, Ames, Iowa 50011

^*Also: Institut für Angewandte Physik, Universität Karlsruhe, 76128 Karlsruhe, Germany.
^†Present address: Department of Physics, Simon Fraser University, Burnaby, BC V5A 16S, Canada.