Route to Room-temperature Superconductivity in Ternary Hydrides at Extreme Pressures

The recent theory-orientated discovery of record high-temperature superconductivity (T_c ~250 K) in sodalitelike clathrate LaH₁₀ [1-4] is an important advance toward room-temperature superconductors. Here, we identify an alternative clathrate structure in ternary Li₂MgH₁₆ with a remarkably high estimated T_c of ~473 K at 250 GPa, which may allow us to obtain room-temperature or even higher-temperature superconductivity. The ternary compound mimics a Li- or electron-doped binary hydride of MgH₁₆. The parent hydride contains H₂ molecules and is not a good superconductor. The extra electrons introduced break up the H₂ molecules, increasing the amount of atomic hydrogen compared with the parent hydride, which is necessary for stabilizing the clathrate structure or other high-T_c structures. Our results provide a viable strategy for tuning the superconductivity of hydrogen-rich hydrides by donating electrons to hydrides via metal doping. Our approach may pave the way for finding high-T_c superconductors in a variety of ternary or quaternary hydrides.

[1] F. Peng et al., Phys. Rev. Lett. 119, 107001 (2017).
[2] H. Liu et al., Proc. Natl. Acad. Sci. U S A 114, 6990 (2017).
[3] M. Somayazulu et al., Phys. Rev. Lett. 122, 027001 (2019).
[4] A. P. Drozdov et al., Nature 569, 528 (2019).