Influence of Ca Content on Binding Energy and Cooper Pairing in Ysub1-x/subCasubx/subBasub2/subCusub3/subOsub7-δ/subCompound

摘要

In this research, the influence of calcium content on the binding energy and Cooper pairing is investigated for the high temperature superconducting Y1-xCaxBa2Cu3O7-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 CuO2 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 CuO2 layer as a function of Ca. The calculated results agree very well with experimental results. This happens because the Ca2+ substitution for Y3+ leads to decreasing the distance between the two CuO2 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 CuO2 layers increasing the tunneling probability of holes between the two CuO2 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.