Transport properties of Bi2Sr2Can-1CunO2 n+4 thin films

Abstract

The Hall effect and resistivity have been measured in Bi2Sr2Can-1CunO2n+4 (n=2 and 3) thin films as a function of magnetic field and temperature. In the normal state, the ratio of the normal resistivity to the Hall resistivity (the cotangent of the Hall angle) is found to vary as T2. Three models are able to account qualitatively for such behavior: a bipolaron model, BCS with a Van Hove singularity, and resonating valence bond. Analyses of the resistivity and the Hall effect in the superconducting fluctuations region above Tc clearly demonstrate the two-dimensional character of the 2:2:1:2 compound. The sign reversal of the Hall constant in the vortex state is related to vortex motion. An explanation is presented based on the motion of an antivortex, or a defect of the local vortex lattice, in moving vortex bundles. The calculated activation energy of approximately 730 K agrees well with the measured value of 750 K, and the model gives the correct sign for the Nernst effect.