Current-voltage characteristics near the glass-liquid transition in high-T_c superconductors

Theoretical expressions for the induced DC electric field, E, are derived as a function of the applied current density, J, near the glass-liquid transition temperature of T = T_GL as E(J) = Ẽ(J)[1 + (δE(J)/Ẽ(J))], where Ẽ(J) is the scalable part and δ E(J)/Ẽ(J) is the unscalable part given by a power series of |T_GL - T|^nv(z+2-D) with n ≥ 1. Then the condition of δE/Ẽ ≪ 1 gives a measure of the width of the critical regime, in which E = E(J) is well scalable. The general scaling characteristics of E = Ẽ(J) are the same as those predicted by Fisher and coworkers based on the conventional theories of phase transitions with the scaling hypothesis, while the present theory provides a concrete expression for Ẽ(J). Furthermore, the expressions for the scaled master curves of the AC impedance are derived. The reason, why the observed E vs. J characteristics are scalable over wider ranges of the temperature and flux density than the critical regime, is also discussed.