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Abstract |
Recent reflectance anisotropy studies on the material showed a photobleaching effect in the in-plane components of the dielectric function around 2.2 and 4.1 eV [1]. We present Raman spectra of oxygen deficient YBa2Cu3O7-delta detwinned single crystals taken with laser excitation of 3.7 eV, close to the UV feature in the dielectric function, in search for a signal from the defect-induced Raman modes. While two groups of defect-induced mode at 230 cm(-1) and 600 cm(-1) behave very similar at the 2.2 eV resonance, we find clear differences for UV excitation. A peak at 600 cm(-1) is identified as a copper-oxygen-chain related, defect-induced modes by its Raman selection rules. While this mode is enhanced beyond the strength of the Raman-allowed modes, the group at 230 cm(-1) is absent. Low temperature experiments showed no change of the peak height under illumination, though the peaks are known to photobleach in the visible. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. |
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