Hall voltage sign reversal in type II superconductors
  The Hall voltage sign reversal is consistently explained by the model in which vortices with the superconducting and normal state charge carriers are regarded as three subsystems mutually connected by interactions. The equations of motion for these three subsystems are solved simultaneously and a new formula for the Hall resistivity is obtained. It is shown that it is possible to explain qualitatively experimental data by this model. 
J. Kolacek, P. Vasek