Transverse resistance of YBa2Cu3O7−δ single crystals with different oxygen deficiency

The resistivity of YBa2Cu3O7−δ single crystals across the layers was investigated in the temperature range Tc–300 K and in the range of δ corresponding to the change in Tc from 93 to 33 K. The temperature dependence of the resistivity is adequately described by an empirical expression, which includes “semiconductor” behavior and fluctuation conductivity in the three-dimensional Aslamazov–Larkin model near Tc. For high Tc, the charge carriers are scattered mainly by phonons. For low Tc, scattering by defects dominates; the coherence length ξab(0) and the electron–phonon interaction constant λ reach the values characteristic of conventional (low-temperature) superconductors with strong coupling. Heterogeneity of the samples causes anisotropy of Tc and variable-range hopping conductivity between different phases.