Browsing by Author "Assefa, Mequanint"

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    Study of Spin Fluctuation induced high Temperature Superconductivity: the Case of Cuprate (YBa2Cu3O6:93) and Pnictide (CaNdFeAsF)
    (Addis Ababa University, 2016-06) Assefa, Mequanint; Singh, Pooran (Professor)
    High temperature superconductivity is an interesting and fascinating phenomenon in which certain materials conduct electricity with zero electrical resistance and expulsion of interior magnetic field with superconducting transition temperature higher than 30 K. This was unexpectedly discovered in copper oxide materials by Bednorz andMuller. After this discovery, a search for new high temperature superconducting families began and still going on. In this thesis, we study high temperature superconductivity involving cuprate and pnicides theoretically. In order to look for this, we consider a model Hamiltonian consisting of kinetic energy term, magnetic energy term and electronspin fluctuation term. and we used Green function formalism to calculate superconducting transition temperature and obtain an expression for the superconducting order parameter for high temperature superconductors analytically. We get the superconducting transition temperatures for YBa2Cu3O6:93 and CaNdFeAsF, 92.4 K and 56 K respectively as they being high Tc materials in their respective series. The spin fluctuation/magnon/ as a possible mechanism for high temperature superconductivity is also highlighted, as yet there is no consensus for the mechanism for high temperature superconductivity in these system