We study superconducting transition temperature ( T _ { c } ) of oxygen-doped double-layer high-temperature superconductors YBa _ { 2 } Cu _ { 3 } O _ { 6 + \delta } ( 0 \leq \delta \leq 1 ) as a function of the oxygen dopant concentration ( \delta ) and planar hole-doping concentration ( P _ { pl } ) .
We find that T _ { c } , while clearly influenced by the development of the chain ordering as seen in the T _ { c } vs . \delta plot , lies on a universal curve originating at the critical hole concentration ( P _ { c } ) = 1/16 in the T _ { c } vs . P _ { pl } plot .
Our analysis suggests that the universal behavior of T _ { c } ( P _ { pl } ) can be understood in terms of the competition and collaboration of chemical-phases and electronic-phases that exist in the system .
We conclude that the global superconductivity behavior of YBa _ { 2 } Cu _ { 3 } O _ { 6 + \delta } as a function of doping is electronically driven and dictated by pristine electronic phases at magic doping numbers that follow the hierarchical order based on P _ { c } , such as 2 \times P _ { c } , 3 \times P _ { c } and 4 \times P _ { c } .
We find that there are at least two intrinsic electronic superconducting phases of T _ { c } = 60 K at 2 \times P _ { c } = 1/8 and T _ { c } = 90 K at 3 \times P _ { c } = 3/16 .