Model of electron pairs in electron-doped cuprates

Abstract

In the order parameter of hole-doped cuprate superconductors in the pseudogap phase, two holes enter the order parameter from opposite sides and pass through various [Formula: see text] cells jumping from one [Formula: see text] to the other under the influence of magnetic field offered by the [Formula: see text] ions in that [Formula: see text] cell and thus forming hole pairs. In the pseudogap phase of electron-doped cuprates, two electrons enter the order parameter at [Formula: see text] sites from opposite ends and pass from one [Formula: see text] site to the diagonally opposite [Formula: see text] site. Following this type of path, they are subjected to high magnetic fields from various [Formula: see text] ions in that cell. They do not travel from one [Formula: see text] site to the other along straight path but by helical path. As they pass through the diagonal, they face high to low to very high magnetic field. Therefore, frequency of helical motion and pitch goes on changing with the magnetic field. Just before reaching the [Formula: see text] ions at the exit points of all the cells, the pitch of the helical motion is enormously decreased and thus charge density at these sites is increased. So the velocity of electrons along the diagonal path is decreased. Consequently, transition temperature of electron-doped cuprates becomes less than that of hole-doped cuprates. Symmetry of the order parameter of the electron-doped cuprates has been found to be of [Formula: see text] type. It has been inferred that internal magnetic field inside the order parameter reconstructs the Fermi surface, which is requisite for superconductivity to take place. Electron pairs formed in the pseudogap phase are the precursors of superconducting order parameter when cooled below [Formula: see text].