The competition between superconductivity and spin density wave in sodium doped barium iron arsenide ( ) superconductor

Abstract The interplay between magnetism and superconductivity has awoken profound interest in the field of condensed matter physics. In this thesis the competition between superconductivity and spin density wave in hole doped barium iron arsenic ( ) superconductor has been investigated based on two band model of Hamiltonian. Employing retarded double time temperature dependent green’s function with the two model Hamiltonian, the expression for superconducting transition temperature (Tc) and spin density wave transition temperature (Tm) as a function of magnetic order parameter (M) have been found. The mathematic expression and the graph TC as function magnetic order parameter shows that the superconducting transition temperature does not increase rather it decreases as the magnetic order parameter increase, but the graph of magnetic transition temperature as a function of magnetic order parameter show that SDW transition temperature increases with the increase of magnetic order parameter. The intersection region in merged graphs of Tc as a function of magnetic order parameter and Tm as a function of magnetic order parameter show that the possible coexistence of superconductivity and spin density wave in superconductors exist in some range of order parameter The result that in the merged graph has revealed in abroad agreement with experimental observation.