ANTIFFEROMAGNETISM AND SUPERCONDUCTIVITY IN 𝐂𝐚𝟎.𝟕𝟒 (𝟏) 𝐋𝐚𝟎.𝟐𝟔 (𝟏) (𝐅𝐞𝟏−𝐱𝐂𝐨𝐱 )𝐀𝐬𝟐SUPERCONDUCTORS

ABSTRACT The coexistence of magnetism and superconductivity has recently re-emerged as a central topic in condensed matter physics due to the interplay between magnetism and superconductivity. The coexistence of antiferromagnetic and superconductivity in high temperature superconductor 𝐶𝑎0.74 (1) 𝐿𝑎0.26 (1) (𝐹𝑒1−𝑥𝐶𝑜𝑥) 𝐴𝑠2 has been studied theoretically by considering the two band model Hamiltonian, (which consisting of intraband and interband pairing interactions, and inter-orbital pair hopping). Using one particle thermal Green’s function with mean field theory and two band model Hamiltonian, the mathematical expression for Superconducting transition temperature and antiferromagnetic transition temperature as a function of order parameter for the two band model have been obtained. The phase diagram of the transition temperature and antiferromagnetic transition temperature versus the antiferromagnetic order parameter for the 𝐶𝑎0.74 (1) 𝐿𝑎0.26 (1) (𝐹𝑒1−𝑥𝐶𝑜𝑥) 𝐴𝑠2 system show that the transition temperature decrease as the antiferromagnetic order parameter increase while the antiferromagnetic transition temperature increase as the antiferromagnetic order parameter increase. On the other hand, the coexistence of antiferromagnetic and superconductivity has been demonstrated by merging the two phase diagrams, the transition temperature versus antiferromagnetic order parameter and antiferromagnetic transition temperature versus the antiferromagnetic order parameter the result to be a distinct possibility in 𝐶𝑎0.74 (1) 𝐿𝑎0.26 (1) (𝐹𝑒1−𝑥𝐶𝑜𝑥) 𝐴𝑠2 in the two band model between (2.3 < 𝑀 < 6.07) where, 𝑀 is the antiferromagnetic order parameter. The phase diagrams of the coexistence of antiferromagnetic and superconductivity in the above mentioned superconductors have been drawn which are in broad experimental agreement.