Superconductivity at 215 K in H₃SM (M=Ne, Ar, Kr, Xe, Rn) ternary hydrides

The recent discovery of H₃S attracts great attention due to the confirmed superconducting critical temperature (T_c) of 203 K. Following the previous structure prediction of H₃SXe superconductors, the anisotropic Migdal-Eliashberg (ME) theory is carried out to study the superconducting properties of H₃SM (M=Ne, Ar, Kr, Xe, Rn) under pressure. We identify a new H₃SRn ternary hydride, with T_c of about 215 K under 240 GPa, belonging to two-gap superconductors with multi-band. H₃SNe exhibits remarkable superconductivity with an anomalously low stabilization pressure (P_s) of about 60 GPa. With the motivation of discovering superconductors at the lowest possible pressure, the chemical pressure is quantified based on the same volume-strain effect of physical pressure and chemical pressure. In H₃SM, the larger the chemical pressure of the central atom, the larger the physical pressure required for its stabilization. Away from the phase transition, decreasing pressure is beneficial to the superconductivity of the H₃SM system. These findings open new avenues for designing and optimizing new high-T_c superconductors with low-P_s.