Study of Spin Fluctuation induced high Temperature Superconductivity: the Case of Cuprate (YBa2Cu3O6:93) and Pnictide (CaNdFeAsF)
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Date
2016-06
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Addis Ababa University
Abstract
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
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High Temperature Superconductivity