Sign Change of the Flux Flow Hall Effect in HTSC

A novel mechanism for the sign change of the Hall effect in flux flow region is proposed. The difference delta n between the electron density at the center of the vortex core and that far outside the vortex causes the additional contribution to the Hall conductivity delta sigma(xy) = -delta nec/B. This contribution can be bigger than the conventional one in the dirty case Delta(T)tau < 1. If the electron density inside the core exceeds the electron density outside the core the double sign change may occur as a function of temperature and magnetic field.