Superconducting ${\mathrm{H}}_x\mathrm{Y}{\mathrm{Ba}}_2{\mathrm{Cu}}_3{\mathrm{O}}_7$: The role of H

The role of H in superconducting ${\mathrm{H}}_x\mathrm{Y}{\mathrm{Ba}}_2{\mathrm{Cu}}_3{\mathrm{O}}_7$ ($0.14<x<\mathrm{}5.0\mathrm{}$) has been examined in infrared (ir) and x-ray absorption spectroscopy (XAS) measurements. The ir studies indicate the formation of Cu-H bonds and a hybride-phase precipitation. The XAS measurements of one of the samples, ${\mathrm{H}}_{1.0}$Y${\mathrm{Ba}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$, show a partial reduction of the ${\mathrm{Cu}}^{2+}$ state to the ${\mathrm{Cu}}^{1+}$ state and deformation of both the Cu(1) and Cu(2) sites. The XAS results also confirm that H is located interstitially only near Cu sites.