Previous measurements show that the thermal conductivity of $Y Ba sb2 Cu sb3 O sb{7- delta}$ in the basal plane is anisotropic with a large peak in the superconducting state. The magnitude of this anisotropy in the superconducting and normal states, and the dominant mechanism for heat conduction in the superconducting state are currently the subject of debate. We have measured the thermal conductivity of high quality $Y Ba sb2 Cu sb3 O sb{7- delta}$ for deoxygenated, twinned and detwinned samples along the a and b axes to shade light on this issue. We were able to measure the electrical and thermal conductivity using the same contacts and hence determine the Lorenz number L = $ kappa$p/T accurately. / Attributing the normal state anisotropy in the heat transport to electrons in the Cu-O chains, the Lorenz number takes on its full Sommerfeld value i.e. $L = L sb0.$ Under this assumption, the phonon conduction is about the same in the superconducting and deoxygenated samples. / Our results are discussed in connection with the two possible mechanisms for heat conduction in the superconducting state. We find that although a strong case can be made for the "electronic scenario" whereby the peak is due to rapidly increasing electron mean free path below $T sb{c},$ it is still not compelling at this stage. / In addition, it is found that the thermal conductivity along the a and b axes is isotropic at low temperatures, with a nonzero linear term in $ kappa,$ indicative of some uncondensed electrons as $T rightarrow$ 0. This low temperature isotropy contradicts previous explanations in terms of non-superconducting chains.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.55497 |
| Date | January 1994 |
| Creators | Gold, Ziv |
| Contributors | Taillefer, Louis (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Science (Department of Physics.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001433841, proquestno: AAIMM00023, Theses scanned by UMI/ProQuest. |
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