Conventional superconductivity at 203 kelvin at high pressures in the sulfur hydride system
The authors compressed hydrogen sulfide (H2S) to extreme pressures around 150 GPa, forming a hydrogen-rich phase believed to be H3S, and observed a sharp drop in resistance signalling superconductivity at up to 203 K. A pronounced isotope effect upon deuterium substitution indicated phonon-mediated, BCS-type (conventional) superconductivity. This set a record transition temperature at the time and validated theoretical predictions of high-Tc superconductivity in compressed hydrides.