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We study superconducting transition temperature ($T_c$) of oxygen-doped double-layer high-temperature superconductors YBa$_2$Cu$_3$O$_{6+delta}$ (0 $le$ $delta$ $le$ 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.
Polarized and unpolarized neutron diffraction has been used to search for magnetic order in YBa$_2$Cu$_3$O$_{6+x}$ superconductors. Most of the measurements were made on a high quality crystal of YBa$_2$Cu$_3$O$_{6.6}$. It is shown that this crystal
We present local optical measurements of thermal diffusivity in the $ab$ plane of underdoped YBCO crystals. We find that the diffusivity anisotropy is comparable to reported values of the electrical resistivity anisotropy, suggesting that the anisotr
Most measurements of critical current densities in YBa$_2$Cu$_3$O$_{7-delta}$ thin films to date have been performed on films where the textit{c}-axis is grown normal to the film surface. With such films, the analysis of the dependence of $j_c$ on th
Polarized and unpolarized neutron triple-axis spectrometry was used to study the dynamical magnetic susceptibility $chi^{primeprime}({bf q},omega)$ as a function of energy ($hbaromega$) and wave vector (${bf q}$) in a wide temperature range for the b
The possibility of enhancing desirable functional properties of complex materials by optical driving is motivating a series of studies of their nonlinear terahertz response. In high-Tc cuprates, large amplitude excitation of certain infrared-active l