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

Here we report targeted high-pressure synthesis of two novel high-T-C hydride superconductors, P6(3)/mmc-ThH9 and Fm (3) over barm-ThH10, with the experimental critical temperatures (T-C) of 146 K and 159-161 K and upper critical magnetic fields (mu H-C) 38 and 45 Tesla at pressures 170-175 Gigapascals, respectively. Superconductivity was evidenced by the observation of zero resistance and a decrease of TC 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 HgBa2Cax-Cu2O6+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 Cmc2(1)-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.