Superconductivity to 262 kelvin via catalyzed hydrogenation of yttrium at high pressures*

Binary metal superhydrides have been predicted to reach high critical superconducting temperatures. Recent experimental observations of LaH10±δ has shown them capable of Tc’s up to 250-260 kelvin. Predictions have shown yttrium superhydrides to be the most promising with an estimated Tc in excess of 300 kelvin for YH10. Here we report the synthesis of an yttrium superhydride that exhibits a superconducting critical temperature of 262 kelvin at 182 ± 8 gigapascal. An innovative synthesis procedure utilizing palladium assists the hydrogenation process by protecting sputtered yttrium from oxidation and allowing hydrogen passage to the yttrium film. Phonon-mediated superconductivity is established by the observation of zero resistance, an isotope effect and the reduction of Tc under an external magnetic field. The upper critical magnetic field is ~103 tesla at zero temperature. Using theoretical predictions, we suggest YH9±δ is the synthesized product based on comparison of the measured Raman spectra .