Effect of surface charge and s-wave component on (001) surface and bulk states of YBa2Cu3O7−δ

The local densities of the (001) surface and bulk states (LDOS) of thin YBa2Cu3O7−δ films were studied based on the self-consistent tight binding model. The CuO-chain and CuO2-plane layers were considered to be a coupling between bands, and then the input surface charge density and the s-wave sub-dominant component were included in the material. In the calculation process, the surface and bulk states were determined, for comparison. It was found that the size of the superconducting gap of a plane layer at the surface increased with an increasing input of the surface charge density, but the LDOS in the bulk were not affected much by this change. When the s-wave component was included in the material, it affected several peaks in the LDOS. This caused some peaks to split while some other peaks became sharper.