Literature and publication status checked through 2026-07-11. This is a retrospective interpretation of an unusually fast episode, not a quantitative study of all replication activity or media coverage.
July 22, 2023
On a Saturday morning in late July 2023, two preprints appeared on arXiv. They were submitted by researchers affiliated with the Quantum Energy Research Centre in Seoul — Sukbae Lee, Ji-Hoon Kim, and colleagues — and they claimed something that condensed matter physicists have been chasing for over a century: a material that superconducts at room temperature and ambient pressure.
The compound was called LK-99. It was a copper-doped lead apatite, synthesized from common precursors using a procedure that, on paper, any moderately equipped laboratory could attempt. The claimed critical temperature was above 400 K — well above 293 K, which is room temperature, which is roughly the temperature of a warm afternoon in Seoul in July.
A video circulated almost immediately. A small, grey, irregular piece of LK-99 appeared to be partially levitating — tilting up, one end raised — above a permanent neodymium magnet. In the video it wobbles slightly, like something caught between gravity and an invisible hand.
Physics Twitter — I will use that name; it was still recognizably that in July 2023 — detonated. Within 72 hours, laboratories across the world were racing to synthesize LK-99. Discord servers formed. GitHub repositories appeared with shared synthesis protocols. Preprints from independent groups began accumulating before the original authors had likely had a good night’s sleep.
Within weeks, the evidence available to the field had converged against the claim.
I want to write about what happened in those weeks, because I think the episode is more interesting as sociology of science than as condensed matter physics. Phase-pure crystals were highly insulating and non-superconducting; Cu₂S transitions explained prominent transport anomalies in mixed samples, while small magnetic responses depended on sample composition. The rapid distributed scrutiny is genuinely remarkable, but no single impurity result explains every sample or social response.
Why Room-Temperature Superconductivity Is the Grail
Let me be precise about why this particular claim generates the response it does.
Superconductivity is the phenomenon in which certain materials, below a critical temperature T_c, carry electrical current with exactly zero resistance. Not very low resistance — zero. A current established in a superconducting loop will, in principle, continue flowing indefinitely without any driving voltage. This is not a small quantitative improvement over ordinary conductors; it is a qualitatively different regime of physics.
Most established ambient-pressure superconductors still require cryogenic cooling. Many elemental superconductors have low transition temperatures; magnesium diboride, a conventional compound, reaches about 39 K. Some cuprates reach roughly 138 K at ambient pressure, but cooling, materials engineering and critical-current limits still constrain applications.
Hydrogen-rich compounds reach very high reported transition temperatures under extreme pressure. The 287.7 K carbonaceous sulfur hydride claim was retracted in 2022 and is not a valid record; independently established landmarks include H₃S near 203 K at about 155 GPa. These are diamond-anvil-cell conditions, not an ambient-pressure cable technology.
Room-temperature, ambient-pressure superconductivity could be transformative if a material also supported useful current density, fields, manufacturability, stability and cost. Zero DC resistance would not eliminate grid conversion, contact or AC losses, and it would not by itself make maglev or MRI compact and affordable. Applications depend on properties absent from the phrase “room-temperature superconductor.”
This is why the response to the LK-99 preprints was not hysteria but rather the entirely rational behavior of a community that understood exactly what was at stake if the claim were true.
What LK-99 Was and What It Claimed
LK-99 is chemically expressed as Pb₁₀₋ₓCuₓ(PO₄)₆O, where x is approximately 0.9 to 1.1. It is a lead apatite — the same crystal family as the mineral in tooth enamel — with a fraction of the lead atoms replaced by copper.
The proposed mechanism, as sketched in the preprints, involved Cu²⁺ substituting for Pb²⁺. Because copper has a slightly smaller ionic radius than lead, this substitution induces a local structural distortion. The claim was that this distortion produces a flat electronic band at the Fermi level — and flat bands are associated with strong electronic correlations that can, in principle, give rise to unconventional superconductivity. The analogy to twisted bilayer graphene was implicit in the discussion, though the mechanism is quite different and twisted bilayer graphene superconducts only well below 1 K.
Reading the preprints in late July 2023 was, I confess, a slightly uncomfortable experience. The writing was rushed. The two preprints — submitted by different author subsets from the same group — were internally inconsistent in places. The resistance measurements showed a large drop with temperature, but not zero resistance. The synthesis protocol was described in enough detail to be reproducible, which was good, but the characterization was incomplete in ways that mattered.
Red flags were present from the beginning. The tilted, wobbling video was not sufficient evidence for a Meissner state. Orientation and stability depend on field and sample geometry, and stable suspension can involve flux pinning; no universal horizontal pose follows from superconductivity. Magnetisation and zero-resistance measurements were needed.
And yet. The synthesis was simple. The claim was specific and testable. If there was even a small chance it was real, the imperative to check was overwhelming. So labs checked.
The Replication Wave
What happened over the following weeks was unusually fast and public for condensed-matter replication. This article does not establish that it was unprecedented.
Normally, a replication in physics looks like this: a group reads a paper, decides it is interesting enough to attempt, orders precursor materials, synthesizes the compound (which takes weeks to months), characterizes it with appropriate instruments (more weeks), writes up the results, submits them (more weeks), and eventually publishes — often six months to a year after the original claim, sometimes much longer. The feedback cycle is slow by design: slowness is a feature, not a bug, because it allows careful work rather than hasty work.
The LK-99 replication did not look like this.
Within a week, preprints from independent groups — China, India, the United States, Germany — were appearing on arXiv. Discord servers with hundreds of members were organizing synthesis attempts in real time, sharing thermograms, resistance measurements, and microscope images as they came off instruments. Twitter threads tracked emerging results with the urgency of a live event. A GitHub repository maintained by the community accumulated synthesis protocols, shared data files, and links to new preprints as they appeared.
Some groups reported partial levitation. Others reported anomalous resistance drops. Others — starting almost immediately — reported synthesizing the material and finding nothing unusual at all.
The speed of this was extraordinary not because of any particular organizational effort, but because the incentive structure happened to align with the infrastructure that now exists. Preprints made sharing immediate. Social media made results public the moment they existed. The synthesis was simple enough to attempt in any reasonably equipped solid-state chemistry lab. And the motivation — the prize, if it were real — was enormous. You would not need to tell anyone to work on this. You would have to tell people to stop.
By mid-August 2023 — three weeks after the original preprints — the key debunking papers had appeared. By late August, there was no serious scientific debate remaining.
The Mechanism of Falsification
The levitating video was explained first, and the explanation is both mundane and instructive.
The sulfur-based synthesis route can produce copper(I) sulfide, Cu₂S. It undergoes a first-order structural transition near 378 K with a large resistance change, so mixed samples can show an anomaly near the claimed transition. Later work reproduced the reported transport anomalies and assigned them to Cu₂S.
Magnetic behaviour varied with composition. Phase-pure crystals showed a diamagnetic insulating response plus a small ferromagnetic component attributed as a possibility to Cu-rich clusters; other LK-99-like samples contained magnetic phases. A tilted response to a permanent magnet is therefore not a unique signature of either superconductivity or one impurity mechanism.
Several groups published null or alternative-explanation papers in rapid succession. Kumar and colleagues reported no superconductivity in their sample; Puphal and colleagues found phase-pure crystals highly insulating; Habamahoro and colleagues later reproduced the principal anomalies and associated them with Cu₂S rather than superconductivity. Theory papers explored electronic structure, but calculations alone could neither verify nor falsify the experimental phase.
Different groups produced non-superconducting polycrystalline and single-crystal samples. Phase-pure single crystals were highly insulating. This supported the consensus against LK-99 superconductivity without implying that every anomaly or magnetic response in every mixed sample had one cause.
Daniel Garisto summarized the consensus in a Nature news piece in August 2023 (Garisto, 2023): LK-99 is not a superconductor. The case was closed, with an efficiency that the scientific community should be proud of.
A Useful Contrast: Ranga Dias
The LK-99 episode does not exist in isolation. The preceding years had seen other extraordinary claims of room-temperature or near-room-temperature superconductivity, and the most prominent involved Ranga Dias at the University of Rochester.
Dias was an author on two Nature papers claiming superconductivity at or near room temperature: carbonaceous sulfur hydride in 2020 and nitrogen-doped lutetium hydride in 2023. Both were retracted. The journal records and associated notices, rather than the original claims, govern their publication status. The earlier Dias and Silvera metallic-hydrogen paper received an erratum and remains formally unretracted; criticism is not the same metadata state as retraction.
The contrast is useful only up to a point. The public LK-99 record shows insufficient evidence for the claim and rapid independent testing; it does not let this article determine the authors’ private intent or moral state.
The Dias publications involve formal retractions and documented research- integrity proceedings, a different evidentiary record from a failed preprint replication. Retraction notices and institutional findings should be reported precisely; they do not license me to infer more than those records establish.
How do you tell them apart in real time? In both cases, you had extraordinary claims that passed initial peer review at prestigious venues. In both cases, independent replication failed. The LK-99 falsification came faster, partly because the synthesis was simpler and partly because the community mobilized more broadly. The Dias case took years, and the data manipulation allegations required access to raw data that the research group was slow to provide.
I do not have a clean real-time test for intent. Observable indicators include data availability, cross-instrument consistency, independent replication and responses to requests for verification. Formal judgments about misconduct need the relevant investigative process, not an analogy between cases.
The Sociology of What Happened
Let me step back from the physics and say something about what the LK-99 episode reveals about how science actually functions.
The episode shows that community correction can be fast when a claim is sharply testable, many laboratories can attempt it and incentives are high. Preprints, social media and shared repositories accelerated exchange, alongside formal laboratories and publications. The counterfactual claim that this would once have taken two to five years is not measured here.
The preprints bypassed traditional peer review, letting both the claim and criticism circulate quickly. Journal review was not the mechanism that resolved the public claim on this timescale. Distributed experimental scrutiny provided a faster complementary process; it did not replace all functions of peer review.
This is not an argument against peer review. It is an argument that peer review in the traditional sense — two or three reviewers reading a manuscript over a few weeks — is not the only form that meaningful scientific scrutiny takes.
Social media’s role was ambivalent: it accelerated both the claim and criticism. I saw physicists identify red flags early, while some coverage foregrounded excitement over caveats. This post has no systematic sample from which to judge most physicists or journalists.
The Media, and the Calibration Problem
I want to be specific about the media failure, because I think it matters.
The appropriate headline on July 23, 2023 was something like: “Korean researchers post preprints claiming room-temperature superconductivity; claim is extraordinary and unverified; replication underway.” That headline is accurate. It conveys the genuine excitement — because the claim, if true, would be extraordinary — while conveying the appropriate uncertainty about an unverified preprint from a single group.
Some coverage used discovery or “holy grail” framing. Without a linked corpus, the quoted wording should be read as illustrative rather than a prevalence claim. Calling an unreplicated preprint a discovery would misstate its evidence status.
This is a calibration failure — the same kind of failure I have written about in other contexts. On this blog, I have discussed how LLMs can fail catastrophically when they lack the context to assess whether their confident-sounding output is grounded in anything real (see the car-wash post, and more generally the discussion of context and grounding in more context is not always better). The mechanism in journalism is different but the structure is the same: confidence that is not appropriately calibrated to evidence.
The Bayesian structure is qualitative here. A rare, repeatedly misidentified phenomenon starts with low prior odds. The video and inconsistent preprints had plausible non-superconducting explanations and no independent replication, so their likelihood ratio was not established as large. They could raise a prior without warranting high confidence; this article supplies no numerical prior, likelihood or posterior.
A well-calibrated account would have said “claim, unverified, replication underway.” Many scientists urged that caution, while some researchers and headlines overinterpreted anomalies. A systematic calibration comparison between science and journalism is beyond the evidence assembled here.
This is not a new observation. Science journalists have been criticized for overclaiming since there have been science journalists. But the LK-99 episode is a particularly clean example because the timescale was so short: the calibration failure in the media and the calibration success in the scientific community happened simultaneously, in full public view, and could be compared directly.
I write occasionally about AI systems producing confident outputs that are not grounded in evidence (a theme that runs through recent posts on this blog). LK-99 is a reminder that poor calibration also occurs in human and institutional systems. The shared recommendation is to track confidence to evidence and update on data; the mechanisms and remedies differ across models, laboratories and newsrooms.
What the Scientific Community Actually Did
I want to be careful not to end on a note of pure cynicism about the media and leave the scientific community looking saintly. The community is not saintly.
There were preprints from independent groups that claimed positive results before the falsification was clear — groups that perhaps saw anomalies and wanted to be part of the story. There was social pressure, documented in real time on Twitter, to share exciting results before they were fully analyzed. The Discord servers and GitHub repositories that were genuinely useful for coordination were also, occasionally, vectors for misinformation and premature interpretation.
Evidence converged against the claim through many attempts to verify or refute it, open discussion and later publications. That is the important result; not every contribution was reliable, open or coordinated.
I find this genuinely impressive. The LK-99 episode shows that correction can work quickly under favourable conditions. It does not establish a general rate or reliability for science.
Classical prepublication peer review was absent from the initial claim. Public scrutiny and replication were complementary forms of criticism, not evidence that all journal review could or should be replaced.
The Next Extraordinary Claim
The 2023 LK-99 superconductivity claim is rejected by the evidence reviewed here. Predictions about textbooks, credit or the authors’ careers would be speculation, so I will not use them as conclusions.
The question I am left with is what happens next time.
Further room-temperature-superconductivity claims are plausible in an active, high-reward field. Their truth cannot be assigned from the LK-99 episode, and a future false positive need not repeat the Cu₂S mechanism.
Will coverage improve? I am uncertain. Attention incentives can favour exciting framing, but this article does not measure newsroom incentives or individual journalists’ reasoning.
Will the scientific community respond as effectively? I think so, at least for claims of this kind: testable, synthesis-based, with enough labs in the world capable of attempting replication. The infrastructure — preprints, Discord, shared repositories — exists and is now demonstrated to work. The speed of the LK-99 falsification sets a kind of benchmark.
The episode showed rapid correction under favourable conditions: a clear empirical claim, many capable groups and fast exchange. The original scientific claim failed, and parts of the communication amplified it. The later experimental correction is the success this essay is about.
Whether the media will have learned anything by the time the next extraordinary claim appears — that, I confess, I doubt.
References
Lee, S., Kim, J. H., & Kwon, Y.-W. (2023). The First Room-Temperature Ambient-Pressure Superconductor. arXiv:2307.12008. Retrieved from https://arxiv.org/abs/2307.12008
Kumar, K., Karn, N. K., Kumar, Y., & Awana, V. P. S. (2023). Absence of superconductivity in LK-99 at ambient conditions. ACS Omega, 8(45), 41737–41743. DOI: 10.1021/acsomega.3c06096
Liu, S., & Meng, S. (2023). Symmetry-breaking and the origin of the anomalous properties of LK-99. arXiv:2308.05135. Retrieved from https://arxiv.org/abs/2308.05135
Puphal, P., Akbar, M. Y. P., Hepting, M., Goering, E., Isobe, M., Nugroho, A. A., & Keimer, B. (2023). Single crystal synthesis, structure, and magnetism of Pb₁₀₋ₓCuₓ(PO₄)₆O. APL Materials, 11, 101128. DOI: 10.1063/5.0172755
Habamahoro, T., Bontke, T., Chirom, M., Wu, Z., Bao, J. M., Deng, L. Z., & Chu, C. W. (2023). Replication and study of anomalies in LK-99—the alleged ambient-pressure, room-temperature superconductor. arXiv:2311.03558. arXiv:2311.03558
Garisto, D. (2023). LK-99 isn’t a superconductor — how science sleuths solved the mystery. Nature, 620, 705–706. DOI: 10.1038/d41586-023-02585-7
Snider, E., Dasenbrock-Gammon, N., McBride, R., Debessai, M., Vindana, H., Vencatasamy, K., Lawler, K. V., Salamat, A., & Dias, R. P. (2020). Room-temperature superconductivity in a carbonaceous sulfur hydride. Nature, 586, 373–377. DOI: 10.1038/s41586-020-2801-z (Retracted 2022.)
Dias, R. P., & Silvera, I. F. (2017). Observation of the Wigner-Huntington transition to metallic hydrogen. Science, 355, 715–718. DOI: 10.1126/science.aal1579 (Erratum published 2017; widely questioned.)
Hirsch, J. E. (2021). Rejoinder to “Comment on ‘Absence of magnetic evidence for superconductivity in hydride compounds’” by Dias and Salamat. Physica C, 590, 1353964. DOI: 10.1016/j.physc.2021.1353964
Changelog
- 2026-07-11: Removed a retracted hydride record; corrected levitation, Cu₂S, magnetic-response and replication claims; fixed Kumar et al. metadata; separated formal publication status from intent and bounded the sociology and media-calibration conclusions.
- 2025-09-14: Updated the Cu₂S characterisation: pure Cu₂S is diamagnetic; the ferromagnetism in LK-99 samples comes from impurity phases. Updated the Dias & Silvera 2017 Science paper status: it received an erratum but was not formally retracted (unlike the 2020 and 2023 Nature papers). Updated the Senapati et al. reference to the correct LK-99 debunking literature (the previous arXiv ID resolved to a different paper).