THE FLUX-FLOW HALL-EFFECT IN TYPE-II SUPERCONDUCTORS - AN EXPLANATION OF THE SIGN REVERSAL

We consider a time-dependent Ginzburg-Landau (TDGL) model modified to take into account two mechanisms responsible for the Hall voltage in superconductors: the usual effect of the magnetic field on the normal current, and the vortex traction by the superflow. For the BCS model of superconductivity, the contribution of the vortex traction is proportional to the energy derivative of the quasiparticle density of states. Our theory gives the correct order of magnitude for the Hall angle in the mixed state. It predicts that the vortex-traction mechanism results in a negative Hall angle for the quasiparticle spectrum with a positive energy derivative of the density of states averaged over the Fermi surface, and vice versa. For the Fermi surface with a complicated shape, the sign of the Hall effect in the mixed state can be different from that in the normal state. If the signs are opposite, the Hall angle changes its sign as a function of the magnetic field below H(c2).