Room-temperature superconductivity claims disputed by a new study

The original attempt

In the original paper, researchers found evidence of the superconductivity of nitrogen-doped lutetium hydride at a temperature of 294 K at a pressure of 1 GPa, which means superconductivity at room temperature and pressure. 

They synthesized the compound in a high-pressure and high-temperature environment and then examined its superconducting properties. However, they state that further studies are required to establish the ratio of hydrogen and nitrogen in their sample.

There has been previous research into superconductivity led by the same lead author, and they had reported room-temperature superconductivity exhibited by a carbon-hydrogen-sulfur compound. However, that paper was retracted as the authors did not provide sufficient information for anyone else to recreate the experiment and were evasive when asked to share their data.

Recreating the experiment

In the new study, scientists used high temperature and pressure synthesis techniques to produce the nitrogen-doped lutetium hydride in a dark-blue color, exactly as the original paper. This was supported by the Raman spectroscopy patterns, which were very similar to the original.

They further used energy-dispersive X-ray spectroscopy to confirm the presence of nitrogen in their samples. When testing for superconductivity, the team found that the compound exhibited metallic behavior (meaning it offered some resistance) between 350 K and 2 K at ambient pressure.

They further applied pressure gradually from 2.1 to 41 GPa and observed a change in the color of the compound from dark blue to violet and then to a pinkish red. However, upon measuring the resistance, they found that the compound's metallic behavior improved but did not show superconductivity, even when the temperature was reduced to 2 K.

The study of other properties, such as magnetization, also indicated that the compound did not have superconducting properties. This led them to conclude that the nitrogen-doped lutetium hydride did not have superconducting properties.

Whether the difference in the phenomenon is due to the difference in the nitrogen and hydrogen content of the two samples or something else is yet to be seen. But the publication of this new study should put some pressure on the original authors to clarify the situation. 

The new study has been published in the journal Nature.

Study abstract:

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 Fm3m 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.