Flux-charge analogy and nonlinear response function in HTSC and 2D charge systems

The physics of flux lines in HTSC pinned by strongly correlated defects can be mapped onto charges in two dimensions (2D). Considering the viscous dis sipation of moving vortices during hopping, we find a nonlinear response fu nction. This function is compatible with so far suggested different model b arriers U(J) and able to make a consistent description of the vortex system near transition. A comparison with the seating behavior of the measured is othermal current-voltage curves with YBCO samples shows fair agreement. Thi s nonlinear response function also shows an empirical fit with I-V behavior of some 2D charge systems.