Vortex-boson analogy and the nonlinear response function in high-Tc superconductors near the phase transition

The physics of flux lines in a high-T-c superconductor pinned by strongly correlated defects can be mapped onto charged bosons localized in two dimensions (2D). Considering the Viscous dissipation of moving vortices, we derive a nonlinear response function. This function is compatible with so far suggested different model barriers U(J) and able to make a consistent description of the vortex system near transition. A comparison with the scaling behavior of the measured isothermal current-voltage curves with YBa2CU3O7-delta (YBCO) samples shows fair agreement. This nonlinear response function also shows an empirical fit with I-V behavior of some 2D charge systems.