Enhancement of Conduction along the c Axis in La_<2-x>Sr_xCuO_<4-δ> due to the Impurity Scattering : Condensed Matter: Electronic Properties, etc.

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We have investigated the impurity scattering effect due to a small amount of oxygen deficiency on the anisotropic resistivity of La_<2-x>Sr_xCuO_<4-σ> with σ <__- 0.01 for x = 0.10, 0.15, 0.22 and 0.26. For x where bulk super conductivity is observed at low temperatures, we found that the c-axis conductivity is remarkably enhanced by scattering above the superconducting transition temperature T_c in spite of the negligible effect on T_c and the in-plane conductivity. This enhancement suggests that the conduction along the c axis is nonmetallic and is assisted by the scattering of the carriers confined in the CuO_2 plane. The degree of enhancement decreases with increasing x. Finally, the enhancement becomes unclear for x = 0.26, where the bulk superconductivity vanishes and the conduction becomes fully metallic along any directions. This is consistent with the idea that the two-dimentionality of the normal electronic state plays an important role in the occurrence of superconductivity at low temperatures.
社団法人日本物理学会の論文
2000-04-15