Electronic and two-magnon light scattering in oxide superconducting crystals |
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Authors: | A A Maksimov and I I Tartakovskii |
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Affiliation: | (1) Institute of Solid State Physics, Russian Academy of Sciences, 142432 Chernogolovka, Moscow District, Russia |
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Abstract: | From investigations of two-magnon Raman scattering (RS) under high pressures up to 430 kbar in Eu2CuO4 and YBa2Cu3O6.2 crystals, it was shown that the dependence of the superexchange integralJ on the distance between Cu and O atoms in CuO2 planesa is anomalously weak (J a–n, n=3±0.5). The large value ofJ indicates strong initial overlapping of Cu and O wave functions in high-T
c
, materials. It was found that an increase in free carrier concentration results in a rapid increase of magnon damping and the disappearance of the two-magnon peak from RS spectra. A detailed study of electron Raman scattering has been carried out in superconducting and insulating YBa2Cu3O6–x
, single crystals. The spectral redistribution at frequencies <600 cm–1 in different polarizations indicate that the superconducting gap is strongly anisotropic. In the normal (metallic) phase the behavior of the imaginary part of the response functionR ( ) in the polarization (x x ) corresponds to the model of a marginal Fermi liquid, and in the polarization (x x ), this behavior is independent of the temperature. In insulating crystals,R ( ) is independent of temperature toT 200 K in both polarizations. |
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Keywords: | Raman two-magnon scattering superconducting gap |
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