https://doi.org/10.1140/epjb/e2007-00030-x
The oxygen isotope effect on the infrared photo-induced absorption spectra of La2CuO4
1
Jozef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia
2
Laboratory for Neutron Scattering, ETH Zürich and PSI, 5232 Villigen PSI, Switzerland
3
University of Ljubljana, Jadranska 19, 1000 Ljubljana, Slovenia
4
Physik-Institut der Universität Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland
Corresponding author: a Roman.Yusupov@ijs.si
Received:
8
November
2006
Revised:
11
December
2006
Published online:
3
February
2007
The infrared photo-induced spectra of the isotope-substituted stoichiometric La2CuO4 samples were studied at T=20 K. Measured spectra were analyzed within the small polaron hopping theory. A small, but detectable shift of the effective phonon frequency on the substitution 16O to 18O is found for the high-energy surface carrier associated band (~4000 cm-1) and has a value of αO = 0.3 ±0.2. The low-energy band (~1500 cm-1) originating from the bulk carriers doesn't show any difference within experimental error which is fully in agreement with theory predictions. The isotope shifts of the optically active oxygen-related phonon modes are described well by the harmonic approximation.
PACS: 74.72.Dn – La-based cuprates / 72.20.Jv – Charge carriers: generation, recombination, lifetime, and trapping / 74.25.Gz – Optical properties / 74.25.Kc – Phonons
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2007