Impurity effects on superconductors and the electron-phonon interaction

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buir.advisorKim, Yong-Jihn
dc.contributor.authorSavran, Kerim
dc.date.accessioned2016-01-08T20:17:43Z
dc.date.available2016-01-08T20:17:43Z
dc.date.issued2000
dc.departmentDepartment of Physicsen_US
dc.descriptionAnkara : Department of Physics and the Institute of Engineering and Science of Bilkent Univ., 2000.en_US
dc.descriptionThesis (Master's) -- Bilkent University, 2000.en_US
dc.descriptionIncludes bibliographical references leaves 42-50.en_US
dc.description.abstractIn this thesis effects of impurities on superconductors and electron-phonon interactions in metals are studied. The first part deals with the effect of magnetic impurities on superconductors. In particular, we focus on the experimental observation that the effect of magnetic impurities in a superconductor is drastically different depending on whether the host superconductor is in the crystalline or the amorphous state. Based on the recent theory of Kim and Overhauser, it is shown that as the disorder in the system increases, the initial slope of the Tc depression decreases by a factor when the mean free path I becomes smaller than the BCS coherence length which is in agreement with experimental findings. Additionally, the transition temperature Tc for a superconductor, which is in a pure crystalline state, drops sharply from about 50% of Tco (transition temperature of a pure system) to zero near the critical impurity concentration. This pure limit behavior was found in crystalline Cd by Roden and Zimmermeyer. In the second part, the effect of weak localization on electron-phonon interactions in metals is investigated. As weak localization leads to the same correction term to both conductivity and electron-phonon coupling constant A (and Xtr), the temperature dependence of the thermal electrical resistivity is decreasing as the conductivity is decreasing due to weak localization. Consequently, the temperature coefficient of resistivity (TCR) decreases, while t he residual resistivit}' increases. As the coupling constant A approaches zero, only the residual resistivity part remains and accordingly TCR becomes negative. In other words, the Mooij rule turned out to be a manifestation of weak localization correction to the conductivity and the electron-phonon interaction.en_US
dc.description.degreeM.S.en_US
dc.description.statementofresponsibilitySavran, Kerimen_US
dc.format.extentxii, 50 leavesen_US
dc.identifier.urihttp://hdl.handle.net/11693/18257
dc.language.isoEnglishen_US
dc.publisherBilkent Universityen_US
dc.rightsinfo:eu-repo/semantics/openAccessen_US
dc.subjectSuperconductivityen_US
dc.subjectelectron-phonon interactionen_US
dc.subjectmagnetic impurityen_US
dc.subjectweak localizationen_US
dc.subjectMooij ruleen_US
dc.subject.lccQC611.95 .S28 2000en_US
dc.subject.lcshSuperconductor.en_US
dc.subject.lcshSuperconductivity.en_US
dc.subject.lcshElectron-phonon interactions.en_US
dc.titleImpurity effects on superconductors and the electron-phonon interactionen_US
dc.typeThesisen_US

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Dept. of Physics - Master's degree