Electrical and thermal transport properties in high Tc superconductors: effects of a magnetic field

Abstract

Experimental studies of the electric and heat currents in the normal, superconducting and mixed states of high T c superconductors (HTcS) lead to characterization, complementary to data obtained from equilibrium property based techniques. A magnetic field superimposed on the superconducting sample generates magneto-transport phenomena, from which an excess electrical resistivity, an excess thermoelectric power, the Hall or the Nernst effect. Different behavioural effects allow one to distinguish various dissipation mechanisms, like quasi-particle scattering, vortex motion dissipation and superconductivity fluctuations, in particular when the Corbino geometry is used. Moreover bulk measurements of the thermal conductivity and the electrothermal conductivity in a magnetic field give us sure indications of the order parameter symmetry. The location of the mixed state phase transition lines in the technological phase diagram of HTcS are briefly pointed out through precise measurements performed over broad temperature and magnetic field ranges. The results are mainly reviewed with the aim of defining further investigation lines.