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Title: The Variation of Isotope Effect Coefficient α in Impure High Tc Superconductors
???metadata.dc.contributor.*???: Prof. P. Singh
Demelash, Kassa
Keywords: AG-Equation;Superconducting Transition Temperature Tc;Isotope Effect Coefficient;Impurity Effect;Disorder (Defect) Effect
Issue Date: Jun-2005
Publisher: Addis Ababa University
Abstract: The value of the critical temperature Tc and isotope coefficient a could be greatly affected by a number of factors. Among them are the presence of magnetic impurities, non-magnetic impurities, disorder and defects. Following previous calculation of the critical temperature and isotope effect by Singh and Kishore (P. Singh and R. Kishore, J. Supercond. 8, 9 (1995)), Singh et al. (S. P. Singh, R. K. Pandey, and P. Singh, J. Supercond. 9, 277 (1996)), Openov (Phys. Rev. B 58, 9468 (1998)) and Openov et al (Phys. Rev. B 64, 12513 (2001)) we have considered the effect of disorder (defect) on the superconducting transition temperature Tc and isotope coefficient a with in the BCS model. An expression for Tc and a as a function of potential and spin-flip scattering rates is derived by means of Green’s functions technique. This is done with the introduction of the matrix Green function in the Nambu representaarbitrary tion. Thedegree expression of anisotropy for In (^of ) the andsuperconducting (— ) is obtainedorder for a parameter superconductor , ranging with from an isotropic s-wave to d-wave and including anisotropic s-wave and mixed (s+d)-wave as to particular where rcases is the . The totaluniversal relaxation dependence time) andof (^(^) on ) on 6 or tp ip (afor factor a given proportional value of X (a coefficient for anisotropy of the order parameter) is shown in different plots for different cases.
Description: A Thesis Submitted to the School of Graduate Studies of Addis Ababa University in Partial Fulfillment of the Requirements for the Degree of Master of Science in Physics.
Appears in Collections:Thesis - Physics

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