Critical Scaling of Extended Power Law I - V Isotherms near Vortex Glass Transition

In view of the question about the vortex glass theory of the freezing of disordered vortex matter raised by recent experimental observations, we reinvestigate the critical scaling of high T_c superconductors. It is found that the dc current-voltage characteristic of mixed state superconductors has a general form of extended power law which is based on the Ginzburg--Landau (GL) functional in the similar way as the vortex glass theory. Isotherms simulated from this nonlinear equation fit the experimental I-V data of Strachan et al. Phys. Rev. Lett. 87 (2001) 067007. The puzzling question of the derivative plot for the I-V curves and the controversy surrounding the values of critical exponents are discussed.