Mechanisms of electrical conductivity in Y1−xCaxBa2Cu3O6.1 system

Systematic studies of transport properties in deoxygenated Y1−xCaxBa2Cu3O6.1 series allowed to propose a diagram of conductivity mechanisms for this system. At intermediate temperature a variable range hopping (VRH) in two-dimensions prevails. At lower temperature VRH in the presence of a Coulomb gap for smaller x and VRH in two-dimensions for larger x are found. In a vicinity of superconductivity we observe conductivity proportional to T. Thermally activated conductivity dominates at higher temperature. This diagram may be universal for the whole family of undoped high Tc related cuprates.