Anisotropic transport properties of impurity (Co) doped and oxygen controlled single-crystal Bi₂Sr₂CaCu₂O_8+δ: Evidence of temperature-dependent interlayer coupling and a pseudogap

We investigate the effects of impurity (Co) substitution and carrier doping on the anisotropic transport properties of Bi₂Sr₂CaCu₂O_8+δ single crystals, focusing on the interlayer charge dynamics. Our analysis shows that the out-of-plane transport in the Bi₂Sr₂CaCu₂O_8+δ system is well described by the tunneling (Lawrence-Doniach) model. By carefully reducing the oxygen content, deviation from T-linear in-plane resistivity, which is similar the behavior in Ba₂YCu₃O_7-δ , can be observed. On the other hand, the out-of-plane resistivity monotonically increases with decreasing temperature, showing no correlation with the anomalous in-plane behavior.