Possible Superconductivity Transition in Nitrogen-Doped Lutetium Hydride Observed at Megabar Pressure.

The pursuit of room-temperature superconductivity at an accessible synthetic pressure has been a long-held dream for both theoretical and experimental physicists. Recently, a controversial report by Dasenbrock-Gammon et al. claims that the nitrogen-doped lutetium trihydride exhibits room-temperature superconductivity at near-ambient pressure. However, many researchers have failed to independently reproduce these results, which has sparked intense skepticism on this report. In this work, a LuHN sample is fabricated using high-pressure and high-temperature methods. The composition and structural characterization are the same as the aforementioned near-ambient superconductor. In situ X-ray diffraction investigations indicate that a high-pressure phase transition toward Fm m-LuHN occurred in the sample at 59 GPa. The temperature-dependent resistance measurements reveal that two possible superconductivity transition are observed at 95 GPa, with T ≈6.5 K for high-T phase and T ≈2.1 K for low-T phase, arising from the disparate phases in the sample. Resistivity measurements in the Fm m-LuHN phase under varying magnetic fields exhibited characteristics consistent with superconductivity, with an upper critical field μH(0) of 3.3 T measured at 163 GPa. This work is expected to shed some light on the controversy surrounding superconductivity in the nitrogen-doped lutetium hydride system.