Pressure-induced high-temperature superconductivity in ternary Y-Zr-H compounds

Compressed hydrogen-rich compounds have received extensive attention as appealing contenders for superconductors. Here, we found several stable hydrides YZrH₆, YZrH₈, YZr₃H₁₆ and YZrH₁₈, and a series of metastable clathrate hexahydrides in the systematic investigation of Y-Zr-H ternary hydrides under pressure. Electron-phonon coupling calculations indicate that they all exhibit high temperature superconductivity and perform better than the binary Zr-H system. YZrH₆ can maintain dynamic stability down to ambient pressure and keep a critical temperature (T_c) of 16 K. The stable YZrH₁₈ and metastable Y₃ZrH₂₄ with high hydrogen content exhibit high T_c of 156 K and 185 K at 200 GPa, respectively. Further analysis shows that the phonon modes associated with H atoms contribute significantly to the electron-phonon coupling. The hydrogen content and the stoichiometric ratio of Y and Zr closely affect the density of states at the Fermi level, thereby affecting the superconductivity. Our work presents an important step toward understanding the superconductivity and stability of transition metal ternary hydrides.