Temperature dependence of the supercurrent density in bilayer cuprate superconductors

The present work deals with the study of the supercurrent density as a function of temperature and various microscopic interactions that exist in bilayer high temperature cuprate superconducting materials. For this purpose a tight binding bilayer Hubbard Hamiltonian has been considered that includes the in-plane (within CuO2 plane) and out-of-plane interactions. The in-plane component of the model Hamiltonian is just in the BCS form with in-plane hopping energy and effective attractive interaction that comprises on-site and intersite interactions and is responsible to form pairing of the charge carriers within the plane. The out-of-plane part of the Hamiltonian includes single particle tunneling along with intrinsic Josephson like coupling between the planes within the unit cell which is responsible for transfer of single particle as well as Cooper pair from one layer to another and vice-versa, in the superconducting state. The situation for bilayered cuprates considered here is equivalent to a Josephson's coupled SIS junction. To derive the expressions of the superconducting order parameter, carrier density and supercurrent density, we rely on the Green's function equations of motion approach within the simple BCS formalism. The numerical analysis shows that in bilayer cuprates the supercurrent density depend on various in-plane and out-of-plane contributions as well as on temperature in an essential way. Finally, we have compared our theoretical results on supercurrent density with that of recent experimental results on temperature and pressure dependence of supercurrent density in bilayer superconducting cuprate materials and found to be in qualitative agreement. (C) 2002 Elsevier Science B.V. All rights reserved.