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Critical microwave-conductivity fluctuations across the phase diagram of superconducting La2-xSrxCuO4 thin films

Haruhisa Kitano, Takeyoshi Ohashi, Atsutaka Maeda, Ichiro Tsukada

cond-mat.supr-conarXiv:cond-mat/0601243

Abstract

We report a systematic study of the dynamic microwave conductivity near Tc for La2-xSrxCuO4 (LSCO) thin films with x=0.07 to 0.16. The strong frequency dependence of the phase stiffness together with scaling analysis of the ac fluctuating conductivity of superconductivity provide direct evidence for the 2D-XY behavior of nearly decoupled CuO2 planes in underdoped LSCO (x=0.07 and 0.12). On the other hand, the critical exponents for slightly overdoped LSCO (x=0.16) were found to agree with those for the relaxational 3D-XY model, indicating that the universality class in LSCO is changed by hole doping. The implication of these results for the phase diagram of high-Tc cuprates is discussed.

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