Doping state and transport anisotropy in Bi2212 single crystals

Electrical resistivity was studied parallel to the ab -plane as well as along the c -axis of Bi2212 single crystals having both over-doped and under-doped states. The anisotropy within the ab -plane (perpendicular and parallel to the modulated b -axis directions) have been also systematically evaluated. The temperature dependence of ϱ a , ϱ b and ϱ c was strongly dependent on the oxygen composition and the anisotropy factors ϱ c / ϱ a and ϱ c / ϱ b showed a similar dependence ; the more carrier doped crystals showed the smaller anisotropies in each case, while ϱ a / ϱ b showed an opposite dependence.