Superconductivity at 161 K in thorium hydride ThH10: Synthesis and properties

Abstract: Here we report targeted high-pressure synthesis of two novel high-T_C hydride superconductors, P6₃/mmc-ThH₉ and Fm3-m-ThH₁₀, with the experimental critical temperatures (T_C) of 146?K and 159–161?K and upper critical magnetic fields (μH_C) 38 and 45?Tesla at pressures 170–175?Gigapascals, respectively. Superconductivity was evidenced by the observation of zero resistance and a decrease of T_C under external magnetic field up to 16?Tesla. This is one of the highest critical temperatures that has been achieved experimentally in any compound, along with such materials as LaH₁₀, H₃S and HgBa₂Ca_xCu₂O_6+z. Our experiments show that fcc-ThH₁₀ has stabilization pressure of 85?GPa, making this material unique among all known high-T_C metal polyhydrides. Two recently predicted Th-H compounds, I4/mmm-ThH₄ (>86?GPa) and Cmc2₁-ThH₆ (86–104?GPa), were also synthesized. Equations of state of obtained thorium polyhydrides were measured and found to be in excellent agreement with the theoretical calculations. New phases were examined theoretically and their electronic, phonon, and superconducting properties were calculated.