ANISOTROPIC RESISTIVITY AND PARACONDUCTIVITY OF TL2BA2CACU2O8 SINGLE-CRYSTALS

The anisotropic resistivity and paraconductivity of Tl2Ba2CaCu2O8 single crystals were measured. The in-plane and c-axis resistivities are, respectively, approximately 7 X 10(-4) and 10(-1) OMEGA cm at room temperature. The c-axis resistivity decreases with decreasing temperature in the temperature range from room temperature down to the superconducting transition temperature, and the second derivative of rho-c is negative, which is not characteristic of YBa2Cu3O7 and Bi2Sr2.2Ca0.8Cu2O8 single crystals, in which the second derivative is either positive or zero. The in-plane paraconductivity is obtained from the in-plane resistivity, and a method without the critical temperature as an adjustable parameter is employed to obtain the dimensionality. The data show that the superconductivity is two dimensional, but a crossover from two to three dimensions has also been observed near the transition temperature in some samples.