Near room temperature superconductivity in superhydrides at megabar pressures*

Recent predictions and experimental observations of high T_c superconductivity in hydrogen-rich materials at very high pressures are driving the search for superconductivity in the vicinity of room temperature. We confirmed the existence of a new class of such materials – superhydrides (MH_x, with x > 6) – and developed preparation techniques for their syntheses and characterization, including measurements of structural and transport properties, at megabar pressures. Four-probe electrical transport measurements of lanthanum superhydride samples display signatures of superconductivity at temperatures ranging from 150 K to above 280 K near 200 GPa. The experiments are supported by pseudo-four probe conductivity measurements, critical current determinations, low-temperature x-ray diffraction, and magnetic susceptibility measurements. These measurements of near-room temperature superconductivity are in good agreement with density functional and BCS theory-based calculations.