Valence Fluctuations in La2-xSrxCuO4
One of the interesting phenomena occurring in narrow band materials are valence fluctuations. We address this problem for the case of high Tc superconductors1,2,3 here. The characteristic feature of the recently discovered high-Tc superconductors derived from the oxide La2CuO4 is the mixed valence of the copper constituent (Cu2+ and Cu3+), which results from substituting a fraction of the trivalent La-ions by bivalent Ca, Ba or Sr dopants. A similar mixed valence is also found in the two previously discovered oxide superconductors BaPb1-xBixO3 (Bi3+, Bi5+)4 and LixTi2-xO4 (Ti3+, Ti4+)5.
KeywordsMixed Valence Charge Fluctuation Virtual Crystal Approximation Valence Fluctuation Rigid Band Model
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