Absence of near-ambient superconductivity in LuH2±xNy – Nature

Recently near-ambient superconductivity was claimed in nitrogen-doped lutetium hydride¹. This stimulates a worldwide interest about exploring room temperature superconductivity under low pressures. By using a high pressure and high temperature synthesis technique, we have successfully obtained the nitrogen doped lutetium hydride (LuH_2±xN_y) with a dark-blue color and a structure with the space group of ({boldsymbol{Fm}}bar{{boldsymbol{3}}}{boldsymbol{m}}) evidenced by x-ray diffraction. This structure is the same as that reported in ref. ¹, with a slight difference in lattice constant. The Raman spectroscopy also shows similar patterns between our samples and that in ref. ¹. The energy dispersive X-ray spectroscopy (EDS) confirmed the existence of nitrogen in the samples. At ambient pressure, we witness a metallic behavior from 350 down to 2 K. By applying pressures from 2.1 to 41 GPa, we observe a gradual color change from dark-blue, to violet, to pink-red. By measuring the resistance at pressures from 0.4 to 40.1 GPa, we have seen a progressively improved metallic behavior without showing superconductivity down to 2 K. Temperature dependence of magnetization under high pressures shows a very weak positive signal between 100 and 320 K, and the magnetization increases with magnetic field at 100 K, all these are not expected for superconductivity at 100 K. Thus, we conclude the absence of near-ambient superconductivity in this nitrogen-doped lutetium hydride under pressures below 40.1 GPa.