The near room-temperature upsurge of electrical resistivity in Lu-H-N is not superconductivity, but a metal-to-poor-conductor transition

TL;DR

This study demonstrates that the near-room-temperature resistance increase in Lu-H-N is due to a metal-to-poor-conductor transition, not superconductivity, challenging previous claims of room-temperature superconductivity in this material.

Contribution

The paper provides experimental evidence that the resistance change in Lu-H-N is not superconducting but a metal-to-poor-conductor transition, clarifying the nature of the observed phenomena.

Findings

Reproduced the near-room-temperature resistance jump in Lu-H-N.

Identified the resistance change as a metal-to-poor-conductor transition.

Challenged the claim of room-temperature superconductivity in Lu-H-N.

Abstract

Since the discovery of superconductivity in mercury at 4 K in 1911, searching for materials with superconductivity at higher temperatures towards practical conditions has been a primary enduring goal. The recent report of room-temperature superconductivity at near-ambient pressure in nitrogen-doped lutetium hydride (Lu-H-N) by Dasenbrock-Gammon et al. (Hereafter referred as D-G) seems a great step approaching the ultimate goal. Specifically, they claimed evidence of superconductivity on Lu-H-N with a maximum Tc of 294 K at 1 GPa. However, the failure to observe the drastic temperature-dependent resistance change above 200 K in high-pressure synthesized Lu-H-N compounds, a prerequisite for superconductivity, by researchers worldwide in all independent follow-up studies casts a heavy shadow on the authenticity of the claims. The sober questions are: what is the sample that produces the sharp resistance jump near room temperature? What are the reasons for the non-reproducibility of others who follow the D-G method of synthesis and the inscrutable low success rate (35%) in synthesizing the right sample even for the authors in Ref. 1? What causes the observed sharp resistance jump? Here, with a well-controlled experiment protocol, we repeatedly reproduced the near room-temperature sudden change of electrical resistance in the Lu-H-N sample, and we could quantitatively compare its behavior with the initial pure Lu in a normal metallic state. These results enable us to scrutinize the origin for the near-room temperature sharp resistance change, which is attributed to a metal-to-poor-conductor transition rather than superconductivity.