Honors thesis : "Thermal conductivity : application to high Tc superconductors"
Since September 1993 : PhD student in the SUPRAS group. Thesis research supervised by M. Ausloos
The main research field is theoretical solid state physics, mainly the
study of electric and thermal transport properties of high-Tc superconductors
in presence or not of a magnetic field.
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IMEC, vzw
Kapeldreef 75
B-3001 Leuven,
Belgium
phone: (32) (0)16/28.12.11
fax: (32) (0)16/22.94.00
E-mail: <michel.houssa@fys.kuleuven.ac.be>
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- Thermal conductivity of anisotropic materials.
- Transport properties in a magnetic field.
- Low temperature behavior of solids.
- Variational methods of irreversible processes.
- Fluctuation effects on transport properties.
- Vortex state in type II superconductors.
- Symmetry of the order parameter.
- Van Hove singularities.
- Superconductivity in layered systems, Lawrence-Doniach model.
2) M. Houssa, H. Bougrine, M. Ausloos, I. Grandjean, and M. Mehbod,
Thermal conductivity of pure or iron-doped YBa2Cu3O7-d with or
without an excess of CuO
J. Phys : Condensed Matter 6, 6305 (1994).
3) R. Cloots, H. Bougrine, M. Houssa, S. Stassen, L. D'Urzo, A. Rulmont,
and M. Ausloos,
Bi-based 2223 superconducting polycrystalline materials prepared
by either a solid state route or a glassy 'matrix' precursor method : chemical
analysis as well as electrical and thermal transport properties
Physica C 231, 259 (1994).
4) M. Ausloos and M. Houssa,
Magneto-thermal conductivity of high-Tc superconductors : electron-vortex
scattering contribution
J. Phys : Condensed Matter 7, L193 (1995).
5) M. Houssa and M. Ausloos,
Thermal conductivity of superconducting Bi2Sr2CaCu2O8 and YBa2Cu3O7-d
Phys. Rev. B 51, 9372 (1995).
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The temperature dependence of the in-plane electronic contribution to
the thermal conductivity of a d-wave superconductor is calculated within
a variational method. To account for the layered structure of high-Tc compounds,
we consider an anisotropic Lawrence-Doniach energy spectrum for electrons.
The very low temperature behavior of the thermal conductivity of most high-Tc
superconductors as well as the peak structure observed below Tc are quantitatively
reproduced by this model. These results both suggest that the symmetry
of the order parameter of high-Tc superconductors is of dx2-y2-wave type
and concur with the hypothesis that the peak observed in the thermal conductivity
of these materials has an electronic origin.
Electronic thermal conductivity of d-wave high-Tc superconductors in a magnetic field
The influence of a magnetic field on the thermal conductivity of high-Tc
superconductors is described within an electronic dissipation model. We
use the description of the number of carriers as deduced from the electronic
specific heat of a d-wave superconductor in conjunction with the field
and temperature dependence of the scattering rate of normal heat carrying
electrons by quasiparticle excitations in the vortex cores as derived from
second order perturbation theory. The experimental results on various YBa2Cu3O7-d
samples arequite well reproduced with very realistic values of the physical
parameters giving much impact into asserting that such high-Tc superconductors
have a d-wave like symmety.
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