Superconductivity and stability of the novel electron-doped H₃S system under high pressure

As promising candidate materials for high-temperature superconductors, hydrides have attracted much attention. In particular, the discovery of Im3¯m H₃S with a high T_c of 203 K has set off an upsurge in hydride research. As an electron donor, the incorporation of metal in binary polyhydrides is believed to play an important role in stabilizing the crystal structure and improving superconductivity. The novel Pm3¯m H₃SM (M = K, Rb, Sr, Tl, Cs, Ba) systems, which can be regarded as electron-doped Im3¯m H₃S, are discovered to be dynamically and thermodynamically stable under pressure. Unfortunately, their superconductivity is not as good as that of the parent H₃S. As the most promising superconductor among them, H₃STl is predicted to be superconducting with a T_c of 111.7 K under 160 GPa. These findings reveal the intricacy of electron doping in modulating the superconductivity of hydrogen-based superconductors. Electron-phonon coupling (EPC) is found to have a negative correlation with the central frequency ω_c of phonon, which opens new avenues for designing and optimizing novel high-T_c superconductors.