Structural evolution and superconductivity of thorium under high pressure and its modulation.

The recent revelation of elemental scandium exhibiting a remarkably high superconducting critical temperature (T_c) of 36 K under 260 GPa [J. Ying et al., Phys. Rev. Lett., 2023, 130, 256002] has sparked considerable scientific intrigue and attention. In distinction to this exciting study, we focus on the superconductivity of thorium (Th) under high pressure and explore its underlying modulation mechanism. Based on the CALYPSO structure search method and first-principles calculations, we have conducted comprehensively a theoretical study on the structural evolution and superconductivity of Th under high pressure, up to 300 GPa. Two novel structures of Th, Fmmm and Immm phases, are uncovered. Our results indicate that the superconductivity of the face-centered cubic (fcc) phase of Th at ambient pressure is just 2.7 K and the T_c gradually decreases with the increase of the pressure. We propose an effective way to enhance the superconductivity of Th, which is the extrinsic doping of light elements without changing the fcc framework. Most importantly, the superconductivity of ThB is enhanced to 12.4 K under ambient pressure, five times higher than that of the Th metal. The present findings establish a good paradigm to regulate the superconductivity of metallic Th under ambient pressure and offer insights into the structures and superconductivity mechanisms of Th based compounds.