ANOMALOUS HALL-EFFECT IN THE MIXED-STATE OF HIGH-TEMPERATURE SUPERCONDUCTORS

The Hall effect in the mixed state of high-T(c) superconductors (HTSC) is of an anomalous nature: near the transition there is a range of te mperatures and of magnetic fields where the sign of the Hall effect is opposite to that in the normal state. The universality of the phenome non in question is indicative of its connection with some general prop erties of the mixed state of type-II superconductors, namely, with pec uliarities of motion of magnetic flux vortex lines (vortices) in these superconductors. This work puts forward a model accounting for a numb er of vortex motion specific features and providing a possibility to o btain the characteristics of the anomalous Hall effect. The work is ba sed on the phenomenologically generalized results of Bardeen-Stephen a nd Nozieres-Vinen, supplemented with an allowance for a new mechanism of vortex ''friction'' associated with Andreev electron reflection on the interface between the normal core and the superconducting peripher y of a vortex. Within the framework of the model suggested, magnetic f ield (and temperature) dependences of the longitudinal and Hall resist ances of a mixed state superconductor have been calculated at temperat ures nearing T(c). At certain quite realistic parameters which define the forces acting on the vortices, there is a range of magnetic fields and temperatures where the sign of the Hall effect is opposite to tha t in the normal state. The lower limit of this range is the irreversib ility line and the upper limit is the upper critical field.