Pressure effects, anisotropic transport properties and upper critical fields of Bi 2Sr 2CaCu 2O 8+ x single crystals - characterization of needle-like BiSrCaCuO crystals

Abstract

We study the physical properties of Bi 2Sr 2CaCu 2O 8+ x platelet-like single crystals with a zero resistance superconducting transition T c of ≅ 80 K. Normal state electrical resistivity and upper critical fields are more anisotropic than in the YBa 2Cu 3O 7 single crystals. The normal state resistivity along the a-b plane linearly increases with the temperature as in the YBa 2Cu 3O 7 compounds. Along the c-axis, the resistivity is very high and exhibits a metallic behaviour which can be induced by defects instead to be intrinsic. The superconducting transition temperature, T c, increases under pressure at a rate of ≅ 0.2 K/kbar. Superconducting needle-like crystals are also studied. They are not single crystals but are composed of two intergrowing phases. One of them is insulating, the other one superconducting. This last phase could be different from the “2212” one. Similarities between the BiSrCaCuO compounds and La 2CuO 4 compounds are underlined.