Hole carrier transfer by apical oxygen in YBCO

摘要

The electronic structure of high temperature superconductor YBCO is calculated by pseudopotential density functional theory using VASP code for different values of Z_(O(4)). Comparison of the results of equilibrium Z_(O(4)) with other calculation techniques indicates the capability of pseudopotential VASP code in energy band structure calculations for HTSCs. Both charge distribution and band structure calculations indicate the transfer of hole carriers from the CuO chains to the CuO_2 planes with the increase of Z_(O(4)). It is resulted that the increase of Cu(1)-O(4) bond lengths causes the creation of holes in the CuO_2 planes. The redistribution of charge density confirms the charge transfer phenomenon. Also, the increase of Z_(O(4)) causes a decrease in E_F and N(E_F). The hole transfer by moving O(4) towards the CuO_2 planes could be considered for optimization of HTSC properties.