Influence of Ca Content on Binding Energy and Cooper Pairing in Y<sub>1-x</sub>Ca<sub>x</sub>Ba<sub>2</sub>Cu<sub>3</sub>O<sub>7-δ</sub> Compound

Abstract

In this research, the influence of calcium content on the binding energy and Cooper pairing is investigated for the high temperature superconducting () 1 2 3 7 Y Ca Ba Cu O x x − − δ compound where x = 0-0.2). This is done by using model considering that the formation of Cooper pairs happens during tunneling mechanism of holes between the two CuO 2 layers in the YCBCO crystal which are considered as forming adjacent potential wells. In this work, we make some modifications on the mentioned model and a modified equation for the binding energy as a function of Ca concentration is formulated to study the effect of Ca content by considering the change in the distance between the CuO 2 layer as a function of Ca. The calculated results agree very well with experimental results. This happens because the Ca 2+ substitution for Y 3+ leads to decreasing the distance between the two CuO 2 layers and hence potential energy of the system will be decreased. This leads to decreasing the binding energy between the Cooper pairs, and decreasing the distance between the two CuO 2 layers increasing the tunneling probability of holes between the two CuO 2 layers and thus increasing conduction mechanism and thus increasing current density, but this will decrease the energy gap and as a result decrease the critical temperature. The calculated results agree very well with experimental results.