Dresden 2003 – scientific programme

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TT: Tiefe Temperaturen

TT 19: Supraleitung: Elektronenstruktur, Phononen, Tunneln, Ordnungsparameter II

TT 19.10: Talk

Thursday, March 27, 2003, 16:45–17:00, HSZ301

Raman Study of Photoinduced Chain-Oxygen Ordering in RBa₂Cu₃O_7−x single crystals — •Sabine Bahrs¹, A. R. Goñi¹, B. Maiorov², G. Nieva², A. Fainstein², and C. Thomsen¹ — ¹Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstrasse 36, 10623 Berlin — ²Centro Atómico Bariloche, Comisión Nacional de Energía Atómica, 8400 S. C. de Bariloche, Río Negro, Argentina

Oxygen-deficient single crystals of RBa₂Cu₃O_7−x R=Y or Pr exhibit Raman-signals which lose intensity under illumination at low temperatures. They are only visible for light polarized parallel to the copper-oxygen chains along one of the crystal axis. In a first two-laser based experiment, we establish that the bleaching effect of the light is also polarization dependent. This and other known properties support the connection of the measured Raman signals to the copper-oxygen chains, their intensity reflecting the state of disorder of the CuO-chains. The effect is thus closely related to aging and to the persistent photoconductivity effect in the material. From a second set of experiments we report the temperature dependence of the Raman spectra and the intensity decrease. Our results indicate that the bleaching effect is a thermally activated process with an activation energy of roughly 15 meV.