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 behavioral 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.

Magneto-transport characterization of Dy123 monodomain superconductors

“…However one of the contributions seems to originate also in "giant" superconducting fluctuations that are due to the extremely short coherence length [26]. More generally the influence of magnetic field on the resistive transition may be accounted for by the integrated area below resistivity vs temperature curve [27][28][29][30] Fig. 6 shows that this area rises quickly with the field strength and may be fitted by the power law expression as H 1.74 ± 0.03 .…”

Two-bandgap magneto-thermal conductivity of polycrystalline MgB2

“…According to standard thinking for conventional superconductors the introduction of a magnetic field would lead to a decrease in heat conductivity because vortices constitute new scattering centres for heat carriers. This picture provided a qualitative explanation of the field-induced decrease in κ(B) observed in the vortex states of conventional superconductors and high T c cuprates in the investigated regions of the field-temperature plane [27][28][29][30][31][32][33][34][35][36][37].…”

“…The thermal conductivity has been used widely to study superconductors [21], offering important clues about the nature of heat carriers and scattering processes between them, especially in B = 0, and in unconventional superconductors [22][23][24][25][26]-the more so in the superconducting state for which traditional electrical probes such as the electrical resistivity, Hall effect, and thermopower are inoperative. The study of the thermal conductivity has already been an interesting probe of the vortex state of high T c superconductors [27][28][29][30][31][32][33][34][35][36][37] as well as in MgB 2 , in the absence [38][39][40] or presence [41][42][43][44][45] of a magnetic field, sometimes in single crystals.…”