The theory of “electride-carrier” precompression

Room-temperature superconductivity is predominantly observed in high-pressure hydrides, but faces a formidable hurdle: the tendency of these materials to decompose and forfeit their superconducting prowess upon pressure release. Consequently, stabilizing room-temperature superconductivity under ambient conditions has emerged as a pressing concern in solid-state physics. Electrides are unique compounds, possessing exceptional properties attributed to the clustering of high-energy excess electrons within the interstices of their lattices. Our theory outlines a general blueprint for achieving ambient superconductivity through the strategic insertion of hydrogen into the interstitial spaces of electride materials. This ingenious approach harnesses quasimolecular H₂ to sequester high-energy electrons, resulting in a substantial density of electronic states at the Fermi level and fostering robust electron-phonon coupling. We implemented this strategy within the realm of alkali metal electrides, fine-tuning their stability via carrier doping effects, grounded in rigorous quantum chemical analyses of pressure-induced chemical bonds. As a result, the KH₆ compound exhibits an exceptional superconducting transition temperature of 222 K at a modest 10 GPa, outperforming previously reported high-pressure superconductors like H₃S (203 K at 155 GPa) and LaH₁₀ (250 K at 170 GPa). Furthermore, the hole-doped NaH₆ compound demonstrates superconductivity at ambient pressure with a remarkable T_c of 167 K, surpassing the previous record-holder HgBa₂Ca₂Cu₃O₈ with 134 K.