Study of Coexistence of Superconductivity and Magnetism in Gd1+_Ba2−_Cu3O7−_ and UGe2 SUPERCONDUCTORS
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Date
2007-05
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Addis Ababa University
Abstract
The coexistence of superconductivity and magnetism has recently re-emerged as
a central topic in condensed matter physics due to the interplay between magnetism
and superconductivity. The recent discovery of the coexistence of superconductivity(
Sc) and antiferromagnetism(AFM) in high Tc superconductor(HTSc)
Gd1+ Ba2− Cu3O7− has been studied theoretically by considering a model Hamiltonian
consisting of pair interaction, intra and inter atomic Coulomb interactions,
exchange interaction and scattering of Cooper pairs by magnetic moments of the
gadolinium(Gd) ions. Using double time temperature dependent Green’s function
formalism and a suitable decoupling approximation, the coexistence of superconductivity
and antiferromagnetism has been demonstrated to be a distinct possibility
in Gd1+ Ba2− Cu3O7− . The coexistence of superconductivity and ferromagnetism(
Fm) in a ferromagnet UGe2 has also been shown theoretically by considering
a model Hamiltonian and employing the Green’s function formalism. Furthermore,
the variation of the Curie temperature(Tm) with pressure in UGe2 has been examined
and investigated. The phase diagrams of the coexistence of superconductivity
and magnetism in the above mentioned superconductors have been drawn which are
in broad experimental agreement
Keywords: Gd1+ Ba2− Cu3O7− , UGe2, coexistence of superconductivity and
magnetism, superconducting order parameter, magnetic order parameter, antiferromagnetism,
ferromagnetism, Ne’el temperature, Curie temperature, phase diagram.
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Keywords
Gd1+ Ba2− Cu3O7− , UGe2, coexistence of superconductivity and magnetism, superconducting order parameter, magnetic order parameter, antiferromagnetism, ferromagnetism, Ne’el temperature, Curie temperature, phase diagram.