Study of Coexistence of Superconductivity and Magnetism in Gd1+ηBa2-ηCu3O7-δ and UGe2 Superconductors

Kahsay, Gebregziabher (2007) Study of Coexistence of Superconductivity and Magnetism in Gd1+ηBa2-ηCu3O7-δ and UGe2 Superconductors. PhD thesis, Addis Ababa University.

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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+ηBa2−ηCu3O7−δ 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+ηBa2−ηCu3O7−δ. 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+ηBa2−ηCu3O7−δ, UGe2, coexistence of superconductivity and magnetism, superconducting order parameter, magnetic order parameter, antiferromagnetism, ferromagnetism, Ne’el temperature, Curie temperature, phase diagram.

Item Type:	Thesis (PhD)
Subjects:	Q Science > Q Science (General) Q Science > QC Physics
Divisions:	Africana
Depositing User:	Selom Ghislain
Date Deposited:	19 Nov 2018 13:13
Last Modified:	19 Nov 2018 13:13
URI:	http://thesisbank.jhia.ac.ke/id/eprint/7308

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