High-pressure study of CeH₉ and potential metastable superconductivity at reduced pressure

The high-temperature, high-pressure synthesis of superhydride materials has led to the discovery of several high-temperature superconductors under pressure. Among these, CeH₉ exhibits a notably high superconducting critical temperature of up to 115 K at comparatively modest pressures around 100 GPa. This makes CeH₉ an ideal candidate for exploring pressure quench protocols (PQP) in superhydride superconductors. In this study, we performed the synthesis and characterization of CeH₉ under high-temperature and high-pressure conditions, along with evidence of novel transport properties in cerium metal at high pressure. Furthermore, PQP with various conditions are investigated as potential pathways to realizing high-temperature superconductivity in superhydrides at reduced pressures.