History of LK-99 in Timeline
LK-99, a gray-black polycrystalline compound formally known as copper-doped lead‒oxyapatite, has emerged as a potential room-temperature superconductor. First studied in 1999 by a Korean University research team led by Lee Sukbae and Kim Ji-Hoon, the material gained significant attention in July 2023 when preprints were published suggesting its superconducting properties at temperatures up to 400 K (approximately 127 °C or 261 °F) and ambient pressure.
1999: Discovery of LK-99
LK-99, named after its discoverers Lee and Kim and the year of discovery (1999), was first studied as a potential superconductor in 1999 by a team at Korea University.
1999: Early Research on LK-99 at Korea University
Lee and Kim, along with Tong-Seek Chair, began their research on LK-99 at Korea University in the 1990s.
2008: Establishment of Quantum Energy Research Centre
In 2008, Lee, Kim, and other researchers from Korea University founded the Quantum Energy Research Centre (Q-Centre) to further their work in superconductivity.
2020: First Patent Application for LK-99 Filed
Lee and Kim Ji-Hoon filed their first patent application for LK-99 in 2020.
2020: LK-99 Paper Submission and Retraction of Similar Research
Lee and Kim submitted an initial paper on LK-99 to Nature in 2020, but it was rejected. That same year, a similar paper on room-temperature superconductors by Ranga P. Dias was published in Nature but later retracted in 2022 due to concerns about data falsification.
2021: Second Patent Application for LK-99 Filed
A second patent application for LK-99, this time also listing Young-Wan Kwon as an inventor, was filed in 2021.
2021: Proposed Theory for LK-99 Superconductivity
In 2021, Kim Hyun-Tak published a paper describing a new theory suggesting that replacing lead ions with smaller copper ions in LK-99 creates a quantum well that could exhibit superconductivity.
2022: Retraction of Dias's Room-Temperature Superconductor Paper
In 2022, Ranga P. Dias's Nature paper on a different room-temperature superconductor was retracted due to questions about the validity of the data.
March 2023: Submission and Acceptance of Korean-Language Paper on LK-99
A Korean-language paper titled "Consideration for the development of room-temperature ambient-pressure superconductor (LK-99)" was submitted to the Korean Journal of Crystal Growth and Crystal Technology in March 2023 and accepted in April 2023, but it did not receive widespread attention until three months later.
March 2023: Publication of LK-99 Patent Applications
Patent applications for LK-99, filed in 2020 and 2021, were published in March 2023, including a World Intellectual Property Organization (WIPO) patent.
April 2023: Trademark Application for "LK-99"
The Q-Centre filed a Korean trademark application for "LK-99" in April 2023.
July 2023: Kim Hyun-Tak Raises Concerns About First Preprint
In an interview with New Scientist in July 2023, Kim Hyun-Tak stated that the first preprint submitted by Kwon contained "many defects" and was submitted without his permission.
July 2023: Two Preprints on LK-99 Appear on arXiv
Two preprints on LK-99 were posted on arXiv within two hours of each other in July 2023. The first preprint listed Young-Wan Kwon as the third author, while the second preprint listed Kim Hyun-Tak as the third author and included three additional authors.
July 2023: DFT Analysis of LK-99
Sinéad Griffin of Lawrence Berkeley National Laboratory conducted a density functional theory (DFT) analysis of LK-99 in July 2023, suggesting its structure might contribute to superconductivity. However, other researchers argued that the DFT results were not compatible with superconductivity in the described structure.
July 2023: Kwon Presents Findings and Departure From Q-Centre
Kwon presented the LK-99 findings at a symposium at Korea University in July 2023. However, Yonhap News Agency reported that Kwon was no longer in contact with the university and had left the Q-Centre four months prior, according to Lee.
July 2023: Independent Research Groups Begin Replication Attempts of LK-99 Synthesis
Following the July 2023 publication, independent research groups around the world initiated efforts to replicate the synthesis of LK-99. These groups aimed to independently verify the claimed properties of the material and contribute to the scientific understanding of its behavior. Initial results from these replication attempts were expected within weeks.
July 2023: LK-99 Preprints Released
In July 2023, a team from Korea University, led by Lee Sukbae and Kim Ji-Hoon, published preprints claiming that LK-99, a copper-doped lead‒oxyapatite, acts as a room-temperature superconductor at temperatures of up to 400 K (127 °C; 260 °F) at ambient pressure.
July 2023: Replication Attempt Confirms Structure but Fails to Find Strong Diamagnetism
A preprint published on arXiv in July 2023 by a group led by Kapil Kumar documented their replication attempts of the LK-99 experiment. They were able to confirm the structure using X-ray crystallography but did not observe strong diamagnetism.
August 2023: Viral Video of Levitating LK-99 Sparks Excitement and Skepticism
On August 2023, a video from Huazhong University of Science and Technology showing a partially levitating LK-99 sample went viral on Chinese social media, sparking both excitement and skepticism. While the video fueled public interest, experts remained cautious. A researcher from the Chinese Academy of Sciences dismissed the claim as "ridiculous," highlighting the need for rigorous scientific validation.
August 2023: Request for LK-99 Sample and Response from Research Team
In August 2023, the Korean LK-99 Verification Committee requested a high-quality sample from the original research team. The team stated they would only provide the sample after the peer-review process of their APL paper was complete, which was expected to take several weeks or months.
August 2023: Korean Society of Superconductivity and Cryogenics Forms Verification Committee
On August 2023, in response to the unverified claims surrounding LK-99, The Korean Society of Superconductivity and Cryogenics established a verification committee. The committee, comprising experts from Seoul National University, Sungkyunkwan University, and Pohang University of Science and Technology, aimed to scrutinize the claims and provide a definitive conclusion. Initially, the committee expressed skepticism, stating that the available evidence, including the arXiv papers and public videos, did not substantiate the claim of LK-99 being a superconductor.
August 2023: Nature Declares LK-99 Not a Superconductor
On August 16, 2023, Nature published an article concluding that LK-99 is not a superconductor, but rather an insulator, based on statements from a condensed matter experimentalist and several studies.
August 2023: Scientific Community Remains Skeptical of LK-99's Superconductivity
As of August 2023, the scientific community remained unconvinced about LK-99's alleged superconductivity. The available data lacked crucial evidence, such as explanations for LK-99's changing magnetization, specific heat capacity measurements, and demonstration of its transition temperature. The observed magnetic response was suggested to be more likely attributed to a combination of ferromagnetism and non-superconductive diamagnetism rather than superconductivity.
August 2023: Kim Hyun-Tak Releases New Video and Claims About LK-99
In August 2023, Kim Hyun-Tak provided The New York Times with a new video that appeared to show a different sample of LK-99 exhibiting strong diamagnetism. He claimed that high-quality LK-99 samples could exhibit diamagnetism over 5,000 times greater than graphite, suggesting it must be a superconductor.
August 2023: Consensus Emerges That LK-99 is Not a Room-Temperature Superconductor
By mid-August 2023, following numerous replication attempts, the consensus among researchers was that LK-99 is not a superconductor at room temperature and is an insulator in its pure form.
Aug 2023: Synthesis of Single Crystals of LK-99 Disproves Superconductivity
In August 2023, P. Puphal et al. published a preprint describing their successful synthesis of single crystals of Pb9Cu(PO4)6O, which definitively disproved the presence of superconductivity in this specific chemical composition. This finding was later published in APL Materials.
August 2023: Replication Attempts Fail to Confirm LK-99 Superconductivity, Alternative Explanations Emerge
By August 2023, numerous replication attempts failed to provide peer-reviewed confirmation of LK-99's superconductivity. Over 15 notable labs publicly shared their findings, none of which observed superconductivity. Some research pointed to copper-deficient copper (I) sulfide as a potential explanation for the observed magnetic responses, suggesting that its known phase transition and diamagnetic properties could mimic the behavior initially attributed to superconductivity in LK-99.
October 2023: Lack of Expected Superconductivity Properties in LK-99
By October 15, 2023, neither the original LK-99 experiment nor any replications had observed the expected properties of a high-temperature superconductor, raising further doubts about the initial claims.
2023: Publication of Initial Findings on LK-99
A series of academic publications summarizing the initial findings on LK-99 were released in 2023, with contributions from seven authors across four different publications.
February 2024: Peer Review and Analysis of LK-99 Replication Attempts
As of February 12, 2024, no replications of the LK-99 experiment had been successfully peer-reviewed. Several studies pointed to non-superconducting ferromagnetic and diamagnetic properties as potential explanations for the initial observations, particularly a copper sulfide impurity during synthesis.