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=0.0x=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)V=R(I−Ic)a(T). Here, we assume that a(T)=1+Φ0IC(T)/2πkBTa(T)=1+Φ0IC(T)/2πkBT and IC(T)=IC(0)(1−T/TC)3/2IC(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)=1a(TC)=1) below TCTC is attributed to the manifestation of dissipation processes. They have a characteristic temperature TpTp defined via the power exponent as a(Tp)=2a(Tp)=2 and are related to the current induced depinning of Abrikosov vortices. Both TC(x)TC(x) and Tp(x)Tp(x) are found to decrease with an increase of Pr concentration x reflecting deterioration of the superconducting properties of the doped samples.