Manifestation of vortex depinning transition in nonlinear current-voltage characteristics of polycrystalline superconductor Y1-xPrxBa2Cu3O7-δ

We present our recent results on the temperature dependence of current-voltage characteristics for polycrystalline Y1-xPrxBa2Cu3O7-δ superconductors with x=0.0, 0.1 and 0.3. The experimental results are found to be reasonably well fitted for all samples by a power like law of the form V=R(I-Ic)a(T). Here, we assume that a(T)=1+Φ0IC(T)/2πkBT and IC(T)=IC(0)(1-T/TC)3/2 for the temperature dependences of the power exponent and critical current, respectively. According to the theoretical interpretation of the obtained results, nonlinear deviation of our current-voltage characteristics curves from Ohmic behavior (with a(TC)=1) below TC is attributed to the manifestation of dissipation processes. They have a characteristic temperature Tp defined via the power exponent as a(Tp)=2 and are related to the current induced depinning of Abrikosov vortices. Both TC(x) and Tp(x) are found to decrease with an increase of Pr concentration x reflecting deterioration of the superconducting properties of the doped samples