Prediction of high-temperature superconductivity in lithium-doped thorium superhydrides under high pressures

Abstract

Hydrogen-rich compounds with distinct hydrogenic frameworks have recently emerged as promising candidates for high-temperature superconductivity. In this work, we systematically investigate the high-pressure phase diagram of the Li–Th–H system at 300 GPa using an advanced first-principles structure prediction method. A thermodynamically stable phase, Li₂ThH₁₇, containing intriguing H₂₈ and H₂₀ cages, is identified with a superconducting critical temperature, T_c, of 162 K at 300 GPa. This high-temperature value significantly exceeds those of isostructural rare-earth hydrides under the same pressure conditions. The enhancement is primarily attributed to an additional electron–phonon coupling contribution originating from the strong interaction between the high Th f and hydrogen electronic density of states near the Fermi level and medium- to low-frequency phonon modes of the metal sublattice. Moreover, effective hole doping in the isostructural Li₂ThH₁₆ increases the T_c to 194 K. These results offer valuable insights into the superconducting properties of actinide hydrides under extreme pressures.