Resistance peak at the resistive transition in high-Tcsuperconductors

The resistance peak, which is occasionally observed near the resistive transition in high-${\mathit{T}}_{\mathit{c}}$ superconductors, is shown by numerical analysis to arise from a slight inclination of the sample face from the ${\mathrm{CuO}}_2$ planes. This inclination combined with large conductivity anisotropy causes a significant distribution of the current density and reduces the voltage drop between voltage probes, resulting in a very small apparent resistivity and high residual resistivity ratio. In the resistive transition region, on the other hand, the anisotropy abruptly decreases, and the apparent resistance increases and approaches the true value before the resistivity vanishes, resulting in an apparent peak. The resistance peak is therefore a manifestation of the fact that the resistive transition along the c axis is much sharper than that in the ${\mathrm{CuO}}_2$ planes.