Fig. 4: Pressure-induced colour change and evolution of temperature-dependent resistance of LuH2±xNy at different pressures.
a, The optical microscope images of LuH2±xNy at different pressures up to 41 GPa. A colour change from dark blue to violet and pink-red is observed. b, Temperature dependence of the electrical resistance of LuH2±xNy from 2 K to 350 K with pressures up to 40.1 GPa. In most R(T) curves, we can see a metallic behaviour from an intermediate temperature down to 2 K, either in the dark blue or the pink-red states. The R(T) curves at low pressures, such as at 0.4 GPa and 1.1 GPa, show a weak upturn in the low-temperature region, which gradually becomes invisible when the pressure is increased. There is a resistivity hump in the region around 300 K in the low-pressure region.
