https://doi.org/10.1007/PL00011098
Thermal conductivity and thermal Hall effect in Bi- and Y-based high-Tc superconductors*
1
II. Physikalisches Institut, Universität zu Köln, 50937 Köln, Germany
2
Theoretische Physik III, Institut für Physik, Universität Augsburg, 86135 Augsburg, Germany
3
Kristall- und Materiallabor, Universität Karlsruhe, 76128 Karlsruhe, Germany
4
2. Physikalisches Institut, RWTH Aachen, 52056 Aachen, Germany
Corresponding author: a freimuth@ph2.uni-koeln.de
Received:
23
August
2000
Published online: 15 March 2001
Measurements of the thermal conductivity (kxx) and the thermal Hall effect (kxy) in high
magnetic fields in Y- and Bi-based high-Tc superconductors are presented. We describe the
experimental technique and test measurements on a simple metal (niobium). In the high-Tc
superconductors kxx and kxy increase below Tc and show a maximum in their temperature
dependence. kxx has contributions from phonons and quasiparticle (QP) excitations, whereas kxy
is purely electronic. The strong increase of kxy below Tc gives direct evidence for a strong
enhancement of the QP contribution to the heat current and thus for a strong increase of the QP mean free
path. Using kxy and the magnetic field dependence of kxx we separate the electronic thermal
conductivity () of the
-planes from the phononic thermal conductivity
(
). In YBa2Cu3O
shows a pronounced maximum in the
superconducting state. This maximum is much weaker in Bi2Sr2CaCu2O
, due to stronger
impurity scattering. The maximum of
is strongly suppressed by a magnetic field, which we
attribute to the scattering of QPs on vortices. An additional magnetic field independent contribution to
the maximum of kxx occurs in YBa2Cu3O
, reminiscent of the contribution of the
-chains, as determined from the anisotropy in untwined single crystals.
Our data analysis reveals that below
as in the normal state a transport (τ) and a Hall (
) relaxation time must be
distinguished: The inelastic (i.e. temperature dependent) contribution to
is strongly
enhanced in the superconducting state, whereas
displays the same temperature dependence as
above Tc. We determine also the electronic thermal conductivity in the normal state from
kxy and the electrical Hall angle. It shows an unusual linear increase with temperature.
PACS: 74.72.-h – High Tc compounds / 74.25.Fy – Transport properties (electric and thermal conductivity, thermoelectric effects, etc.)
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2001