Progress in High-Pressure Hydride Superconductors: From Theoretical Predictions to Experimental Breakthroughs

The discovery of high-temperature superconductivity in hydrogen-rich compounds at high pressures has reshaped the landscape of condensed matter physics. This review traces the remarkable trajectory of high pressure hydride superconductors, from early conceptual proposals to recent experimental milestones. We begin with the foundational theoretical framework, including Ashcroft's chemical precompression hypothesis and the electron-phonon coupling mechanism that governs conventional superconductivity in these systems. The central experimental achievements are then examined in chronological order: the record breaking 203 K transition in H₃S at 155 GPa, the near room temperature superconductivity at 250-260 K in clathrate structured LaH₁₀, and other experimentally synthesized binary/ternary hydrides with excellent superconducting properties. We also analyze the unifying structural and electronic features responsible for high transition temperatures. Finally, we address persistent experimental challenges, from unambiguous sample characterization to the definitive detection of the Meissner effect, and outline promising strategies toward the ultimate goal of achieving higher superconducting transition temperatures under lower pressures. This review highlights the powerful synergy between first principles theory and diamond anvil cell experiments that has driven this field forward.