Superconductivity Above 80 K in Polyhydrides of Hafnium

Studies on polyhydrides are attracting growing attentions recently due to their potential high temperature superconductivity (SC). We here report the discovery of SC in hafnium polyhydrides at high pressures. The hafnium superhydrides are synthesized at high pressure and high temperature conditions using diamond anvil cell in combination with in-situ high pressure laser heating technique. The SC was investigated by in-situ high pressure resistance measurements in applied magnetic fields. A superconducting transition with onset T c ~83 K was observed at 243 GPa. The upper critical field μ 0 H c2 ( 0 ) was estimated to be 24 Tesla by GL theory and the consequent superconducting coherent length ξ to be ~37 Å. Our results suggest that the superconducting phase is from C 2/ m -HfH 14 . This is the first 5 d transition metal polyhydride superconductor with T c above the liquid nitrogen temperature.