Not the First Room-Temperature Superconductor?
A few weeks ago I reported on a paper on arXiv entitled The First Room-Temperature Ambient-Pressure Superconductor. It presented a material now known as LK-99. The quest for high temperature superconductivity has been very active for many years so this claim generated a lot of interest and LK-99 now has a very active Wikipedia page. Not entirely surprisingly, the claim of superconductivity has been met with some resistance. Geddit?
To summarise, a number of groups seem to have managed to synthesize LK-99, but none have managed to recreate the claimed superconductivity.
This paper on arXiv by scientists at the CSIR National Physical Laboratory in India states:
The report of synthesis of modified Lead apatite (LK-99) with evidence of superconductivity at more than boiling water temperature has steered the whole scientific community. There have been several failures to reproduce superconductivity in LK-99 including partial successes. Here, we have continued our efforts to synthesize phase pure LK-99 with improved precursors. The process has been followed as suggested by Sukbae Lee et. al., [1,2]. The phase purity of each precursor is evidenced by Powder X-ray diffraction (PXRD) and well fitted by Rietveld refinement. The PXRD confirms the synthesis of phase pure polycrystalline LK-99 with apatite structure. The freshly synthesized sample does not show any signature of superconductivity levitation on a magnet (diamagnetism). The magnetization measurements on SQUID also show that LK-99 is diamagnetic at 280 K, there is no sign of superconductivity in LK-99 at room temperature. Moreover, we have also performed first principle calculations to investigate the electronic band structure of the LK-99 near Fermi level. Our study verifies that the Cu doped lead apatite (LK-99) has bands crossing at Fermi level, indicating generation of strong correlation in the system.
arXiv:2308.03544
There is also this paper submitted to arXiv on the same day (7th August) by scientists from the University of Manchester:
Recently, two arXiv preprints (arXiv:2307.12008, arXiv:2307.12037) reported signatures of superconductivity above room temperature and at ambient pressure, striking worldwide experimental research efforts to replicate the results3-7, as well as theoretical attempts to explain the purported superconductivity8-12. The material of interest has chemical formula Pb10−xCux(PO4)6O, where x≈1, and was named by the authors as LK-99. It belongs to lead apatite family, and was synthesized from two precursors, lanarkite (PbSO4⋅PbO) and copper phosphide (Cu3P). Here we performed a systematic study on LK-99, starting from solid-state synthesis, followed by characterisation and transport measurements. We did not observe any signatures of superconductivity in our samples of LK-99.
arXiv:2308.03823
While other studies suggest that LK-99 may have some interesting magnetic properties, it’s not looking good for this as a room-temperature superconductor, or indeed any kind of superconductor at all. I would like to see a few more results published before deciding firmly that the matter is closed, but I don’t think I’ll be buying shares in LK-99.
P.S. Nobody should get too overwrought if the claim is refuted: it’s an example of a thing called the scientific method.
In the Dark 
August 15, 2023 at 11:42 am
I was concerned that the new paper offered a theoretical explanation using Hirsch’s mechanism for pairing fermions into bosons, that then fill the ground state and superconduct. Hirsch’s mechanism is to do with the pairing of holes (rather than electrons), and offers a unified explanation of low-T superconductivity (previously explained by BCS theory) and high-T superconductivity. That would be nice. But changing isotopes in the lattice has an effect consistent with BCS theory but inconsistent with Hirsch’s.
If the claims are untrue, then what was going on in that lab such that the claim was made on the arXiv? On the side of rapid publication – before the experiments are done properly – is desire to be the first; on the other side is desire not to look foolish before the whole world. That’s quite a tension. Did it cause a rift in the group?
Nothing this entertaining since cold fusion…
August 15, 2023 at 11:53 am
Well, there is another preprint on the same material but not all the authors of that are on the superconductivity one, so perhaps there was a falling out?