Site dependence and peak assignment of YBa2Cu3O7-x O K edge electron energy los near edge fine structure...

The different peaks in the O-K edge near edge fine structure (ELNES) of YBa2Cu3O7-x (YBCO) are interpreted here by using overlap population diagram. This study identifies the peaks in the spectrum as follows: 1) The first peak purely originates from O-Cu interactions, 2) the contributions from Y, Ba, and Cu are comparable at the second and third peaks, 3) and the fourth peak has the largest O-Cu interactions. Therefore, the first/fourth peaks and second/third peaks can be sensitive to the changes in the atomic and electronic structure at Cu and Y/Ba sites, respectively. The causes of the spectral differences depending on the atomic site are also discussed.