The thermal conductivity $ kappa$ of the high-temperature superconductor $ rm YBa sb2Cu sb3O sb{7- delta}$ has been the subject of numerous investigations in recent years. Previous measurements show that $ kappa$: (1) exhibits a large peak in the superconducting state; (2) is anisotropic in the basal plane of the orthorhombic crystal structure. The main two subjects of this thesis are: (1) the origin of the peak and (2) a detailed investigation of the anisotropy. / In order to investigate the relative contribution of electrons and phonons to the heat conduction in YBCO, we have measured the thermal and electrical conductivities of high-quality twinned and detwinned crystals, with different levels of Zn-doping (from 0% to 3%). We found that the peak was rapidly suppressed by the impurities. Two scenarios are used to explain our results, attributing the effect to decrease in the carrier mean free path of either the electrons or the phonons. / As for the anisotropy between the a-axis and the b-axis, only two previous studies had previously been done. We find some new striking features: (1) a peak appears in $ kappa sb{chain}$ below 50 K, revealed as a result of our using of higher purity samples. (2) this peak is similar to that of $ kappa sb{a}$ below $T sb{c} (i.e., kappa sb{plane}),$ which we take as the evidence for the growth of superfluid density in the chains below 60 K. We discuss these results in terms of a model of single-electron tunneling between chains and planes.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.27392 |
| Date | January 1996 |
| Creators | Pu, Song, 1968- |
| Contributors | Taillefer, L. (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: 001556196, proquestno: MQ29767, Theses scanned by UMI/ProQuest. |
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