Emergence of superconductivity in Th3P4-type Sn3Se4 and Ge3S4 under high pressure synthesized by diamond anvil cell with boron-doped diamond electrodes.

High-pressure techniques provide a powerful approach for exploring superconducting materials by enabling structural modifications that significantly alter electronic and phonon properties. In this study, we investigate the emergence of superconductivity in Sn3Se4 and Ge3S4 with the Th3P4-type cubic structure using high-pressure synthesis and in situ electrical transport measurements in a diamond anvil cell equipped with boron-doped diamond electrodes. Both compounds exhibit superconductivity, with maximum transition temperature T c of 7.9 K at 8 GPa for Sn3Se4 and 10.5 K at 11 GPa for Ge3S4. The behavior of the T c as a function of pressure and previously reported theoretical calculations, including related compounds, suggest a phonon-mediated BCS-type mechanism for observed superconductivity. These results expand the family of Th3P4-type superconductors and demonstrate the effectiveness of high-pressure techniques for discovering new superconducting phases.