An evidence of the three-dimensional superconductivity evolution through apical oxygen in YBCO

Superconductivity in the high-T_c cuprates originates from transport phenomena in their universal structural CuO₂ plane. Meanwhile, the role of the apical oxygen which locates between CuO₂ planes has brought significant attention. This is because the superconducting temperature (T_c) varies based on cuprates, even though they have the same CuO₂ structure and doping. Here, we investigated the oxygen order at the Cu-O chain layer in YBa₂Cu₃O_6.73 (YBCO), which is connected with CuO₂ plane through the apical oxygen. For this purpose, we performed resonant soft x-ray scattering measurement around the Cu L₃-edge. We found that the evolution of the three-dimensional (3D) superconductivity in YBCO is strongly correlated with the oxygen order. More details will be introduced in the presentation.