Synthesis and Physical Properties of Tl-O Monolayer Superconductors: T1Ba1+xLa1−xCuO5and TlBa2Y1−xCaxCu2O7

Abstract

Abstract Two systems of Tl-based copper oxides with a Tl-O monolayer structure, TlBa2Y1−xCaxCu2O7 (1212 phase) and TlBa1+x La1−xCuO5 (1201 phase), have been synthesized. For x = 0, where formal Cu valences in both systems were estimated to be just +2, samples exhibited semiconductive or insulating behaviors in the resistivity measurement. With increasing x, electrical properties of samples became more metallic and superconductivity appeared. For the 1201 phase, the maximum Tc value was about 40K at around x = 0.2, and sample became a metallic nonsuperconductor for x> =0.4. For the 1212 phase, maximum Tc value was about 90K at around x = 0.8 and metallic nonsuperconductivity was not observed.