This is translated version of [LK-99 논문들에 관해](https://hackmd.io/@sanxiyn/S1hejVXo3)

Mostly done by DeepL but corrected errors incuding opposite or ambiguous meanings and proper names. Please report if you find any ambigious sentence still remains.

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2023-07-30

Credits: Sanghyeon Seo (서상현, Research analysis and writing), Seonghoon Kang (강성훈, Discussion and writing including drafting), Joongi Kim (김준기, Discussion and writing)

Disclaimer: This roundup consists of our findings based on published papers, media reports, etc. and extrapolations of what is known to date. We expect that the actual success of LK-99 will be revealed through cross-validation by other researchers in the near future, and we hope that these efforts, regardless of success, will pave the way for better R&D results in the future. The people who conducted the research and discussions are not experts in physics and superconductors, but ordinary people who understand how academia and the paper publishing system work.

## Introduction

We would like to take a look at the synthesis of the LK-99 material and the papers analyzing it, which have recently become a hot topic, claiming to develop a room temperature normal voltage superconductor. People are curious about it but they are getting even more confused about it. Multiple reasons caused it since the topic has suddenly become a hot topic, several papers about it have been published, and media interviews and conference presentations have been mixed up. We have tried to explain the current situation as best we can based on the publicly available information.

This summary is not a scientific analysis, but rather a reference to understand the historical context behind the announcement of LK-99, a substance that seems to have fallen out of the sky. In particular, additional cross-validation and publications by research groups may reveal new facts or reveal aspects of the story that differ from those summarized in this article.

## Superconduct

...

*Translator's note: I skipped this section since this is general scientific and technical background of superconduct.*

## People

### Tong-Seek Chair (최동식)

Professor Emeritus of Chemistry at Korea University. One of the key person present at the beginning of LK-99. People say, he was very influential in the critical period of chemistry department of Korea University. (verification needed)

Apparently motivated by the discovery of high-temperature superconductors in 1986 and worked on the theory that would make room-temperature superconductors possible.

In 1993, presented the Inter-atomic Superconducting Band (ISB) theory, which was not accepted. See [Maeil Business 1994-09-09](https://www.mk.co.kr/news/economy/1346936) for reaction at the time.

Translator's note: An article about the theory in 1993 [벽에 부딪친 초전도 연구에 돌파구 제시한 고려대 최동식 교수](https://mdl.dongascience.com/magazine/view/S199309N024)

In 1994, he published a book called [Theoretical Framework of the Superconductivity Revolution](https://kupress.com/books/3248/)(초전도혁명의 이론적 체계), a collection of papers and essays(?) including this theory. It is said that he considered "the impact and meaning of the superconducting revolution, which is so certain to be implemented, on humanity." The content is... well...

Since then, he has continued to develop candidate substances to prove the ISB theory, and LK-99 is one of them. Discovered in 1999, LK-99.

Translator's note: Skipping extra note about discovery of high temperature superconduct.

### Sukbae Lee (이석배), Jihoon Kim(김지훈)

- Sukbae Lee: Assistant(Visiting? Adjunct?) Professor at Korea University → Adjunct Professor at Dongguk University → CEO of Quantum Energy. Research Centre, Inc
- Jihoon Kim: Graduate student at Korea University → Director of ICELTECH → Director of Quantum Energy. Research Centre, Inc
[Jihoon Kim's LinkedIn](https://www.linkedin.com/in/ji-hoon-kim-03508b80)

These are the original creators of the hot topic LK-99. They are the first and second authors of all three papers we refers in this article. They found LK-99 is a potential superconduct at this time - more description later - but it was not exactly proven yet. Eventually, the research was stucked after both of them left academia.

Sukbae Lee apparently did not get tenure. He seems having been taught computer science (?!) at Dongguk University. Jihoon Kim devoted himself to battery research and known to be a key person to make [ISELTEK CO.,LTD.](http://icelltech.com/)(아이셀텍) as a global powerhouse in the hearing aid battery industry.

Tong-Seek Chair died in 2017. He regretted that he did not confirm the potential of ISB theory and LK-99 and left a will requesting further research. (This can be found in the Acknowledgments of the papers)

Circumstantial evidence suggests that the funding was provided by members of the lab at the time. The investors listed in the acknowledgments have nothing in common except that they seem to be related to chemistry, so this may be the main link between them.

In 2017, with this funding, the Quantum Energy Research Centre began developing a room-temperature, normal-pressure superconductor. Although it is called funding, it does not seem to have been enough to do satisfactory experiments. We can check the large contributions of Young-Wan Kwon and Hyun-Tak Kim, who participated in the measurement of the sample in the papers.

### Young-Wan Kwon (권영완)

Research Professor at Korea University and KIST, CTO of Quantum Energy Research Institute (~ early 2023)

Young-Wan Kwon was not a founding member of Quantum Energy Research Centre, but became involved during the course of a joint research project.

According to Paper 1, Young-Wan Kwon's research topic was related to the magnetic properties of LK-99. They tried to observe LK-99 using EPR spectroscopy in a similar way with his help.

The papers were supported by the National Research Foundation of Korea(한국연구재단) and Korea University in 2019. By looking paper 3, the support was not monetary, but quata of Superconducting Quantum Interference Device (SQUID) from the foundation, which was necessary for the paper.

Kwon also gave a presentation at [MML 2023](https://www.mml2023.org/) in 2023-07-28. It is reported that not originally prepared but the organizers(Korea University) hastily hold after the last talk when the LK-99 news broke. Since it was not well prepared, the presentation seems to have been reused from the one made for the company's funding, and he asked for a translator because he felt difficult to make a speech in English. He also brought samples, but couldn't demonstrate them because he didn't have any lab equipment.

### Auh Keun Ho (오근호)

Professor Emeritus, Hanyang University
Member of Quantum Energy Research Centre.
Founder of KCI(Journal of the Korean Crystal Growth and Crystal Technology, 한국결정성장학회) where paper 1 was published.

### Hyun-Tak Kim (김현탁)

The chief of Center for MIT Creative Research, ETRI → Research Professor, College of William & Mary (2022-)
Responsible for writing Paper 3

Hyun-Tak Kim is the most well-known of the authors in the academic community. Take a look at his [Google Scholar profile](https://scholar.google.com/citations?user=_P8mux4AAAAJ). h-index is 45.

At a glance, he appears to be a later joiner, similar to Youngwan Kwon, but it is more fascinating.

Hyun-Tak Kim suggested a new theory of the metal-insulator transition (MIT) in 2004, which was not recognized at the time. However, in 2007, he came back with concrete experiments and proved the theory. He is now well recognized for the theory. This is also the meaning of "MIT" in the Center for MIT Creative Research, where Hyun Tak Kim was the chief. (Depending on the context, MIT is sometimes written as IMT in reverse order)

Though the order is unclear, a similar relationship exists between LK-99 and BR-BCS theory (published in 2021). The BR-BCS theory is a combination of the BR theory and the BCS theory, each theory is well recognized, but the combination theory is unlikely to be recognized immediately because it is a combination of theories that are not directly related to each other.

Hyun-Tak Kim seems to be trying to use LK-99 to prove BR-BCS theory, as he did at MIT in the past. In 2007, he submitted to Science, so this time to Nature...? According to the schedule, in 2024. By the timeline, we guess he quitted ETRI to study BR-BCS.

## Papers

### Paper 1: Reflections on the development of a room temperature ambient pressure superconductor (LK-99)
Korean title: 상온상압 초전도체(LK-99) 개발을 위한 고찰

Journal of the Korean Crystal Growth and Crystal Technology 33(2) 61-70, received 2023-03-31
https://doi.org/10.6111/JKCGCT.2023.33.2.061

This seems to be the paper that best represents the opinions of the original developers, including Tong-Seek Chair, Suk-Bae Lee, and Jihoon Kim. Of course, it is very messy and unorganized, more like a 10-year diary than a paper. It seems that Professor Auh Keun Ho played a big role in the fact that such a paper could be published in a journal even though it was IF 0.25 (...)...

(Prof. Auh also published a review on superconductors in the same journal in 2021, but it is not available online)

#### The Story Behind the Development of LK-99 (p. 65)

Fig. 3 shows why LK-99 attracted so much attention in 1999. According to the paper, by chance, a particular sample showed a peculiarity in magnetization that appeared to be a critical temperature between 300 K and 350 K. Attempt to reproduce it yielded similar results from two additional samples.

However, the yields and the purity were too low to study the structure at the time. When they restarted further attempts in 2017, the team established a manufacturing process that significantly increased yields, making it possible to study the structure.

There was a lot of controversy since the sample was half-floating in the subsequent video. If LK-99 is indeed a superconductor, we can assume that the process of increasing the purity is still difficult comparing to increasing the yield.

> Extra note:
> The established process is something that other researchers may be puzzled by. The original sample was just a mixture of commonly available [lanarkite](https://en.wikipedia.org/wiki/Lanarkite) and copper phosphide. The established process does not change this, but it just means that the lanarkite and copper phosphide are made from scratch rather than commercially available samples. (The authors have published a detailed protocol for this.) There are possibility of:
> - The specific process of making lanarkite and copper phosphide may affect the molecular structure, leading to superconducting
> - Certain impurities in the sample preparation process may play a critical role.
> A question also can be raised why lead was not previously favored as a material for superconductors, which could be explained by the fact that the "theory" that lead was unsuitable was established early on, and the search for superconductors using lead was stalled.

#### Tong-Seek Chair's Theory (p. 64)

Chair's argument is that superconductors are a type of liquid, and therefore the theory of ordinary liquids should apply similarly. Specifically, he argues that the heat capacity property of superconductors is statistically equivalent to the [Lambda point](https://en.wikipedia.org/wiki/Lambda_point), but this possibility was not properly considered since Lambda point theory was established after BCS theory.

Based on these theoretical arguments, Chair searched for narrowed conditions to increase the critical temperature, and the resulting possibility was a so-called one-dimensional metal, i.e., a material that behaves like a metal in only one axis. According to the argument, this limited freedom is responsible for raising the critical temperature. (The theories in Papers 2 and 3 seem to have a similar view of one-dimensional metals, although the subsequent development is different.)

On p. 68, the authors write that this theory will be "organized and published in an international journal," but it has not yet been published.

#### Measured Properties (pp. 67-68)

Electrical (Fig. 6), magnetic (Fig. 7/8), and chemical (Fig. 9) properties. Critical Temperature was $T_c = 370~\mathrm{K}$. The lower critical temperature than the later published 400 K is likely due to the earlier date of this study.

Characteristically, there is a heat capacity graph here that is missing from the other papers.

#### Auh Keun Ho's theory (p. 68)

A light (?) theoretical discussion of the measured properties appears. In addition to the aforementioned theory of Tong-Seek Chair, there is a discussion of apatite structure, so it is a one-dimensional metal... blah blah blah, which seems to be influenced by the theory of Auh Keun Ho which is also in references.

### Paper 2: The First Room-Temperature Ambient-Pressure Superconductor

https://arxiv.org/abs/2307.12008 (v1 2023-07-22)

A later paper posted by Youngwan Kwon without authorization from the research group. The authors are only Youngwan Kwon except for the two main developers, and the rest are only referred in Acknowledgments.

**Young-Wan Kwon's theory**

The overall content is not much different, but this paper mentions superconducting quantum wells (SQW) for theoretical reasons. This seems to be an original work of Young-Wan Kwon's, as it is completely unrelated to the other papers.

While other papers mention the reduction in volume due to the doping of copper ions, this paper outright claims that the reduction in volume induces superconductivity. This appears to be Kwon's own theory.

**Target Journal**

Based on the interview, this paper was likely intended for submission to Nature (or a later version). Nature requires unconditional separation of Supplementary Materials compared to other journals, and papers targeted for Nature have a different structure than other papers.

For similar reasons, paper 3 can be seen as a paper that was intended for APL Materials.

### Paper 3: Superconductor $\mathrm{Pb_{10-x}Cu_{x}(PO_{4})_{6}O}$ showing levitation at room temperature and atmospheric pressure and mechanism

https://arxiv.org/abs/2307.12037 (v1 2023-07-22)

A paper that includes all of the remaining authors except Kwon. This is probably the collective work of the entire research group. According to the credits, the overall writing of this paper was done by Hyun-Tak Kim. Thanks to the writing, this paper has best quality of 3 papers.

However, as Hyun-Tak Kim mentioned in his interview, he did not originally intend to publish this paper at this point in time. It seems that he was forced to publish it because of paper 2, even though he already knew it has errors. It is estimated that he organized and posted it within a day, which is why there was bookmark errors. Otherwise, there is no way that a paper to change the world have a bookmark errors.

**Hyun Tak Kim's theory (section III)**

As mentioned earlier, this thesis is another thesis and another theory. For a discussion of BR-BCS, see the Hyun-Tak Kim section.

**Contrubutions by Authors**

An "original draft" is mentioned, which is presumably paper 1. It is labeled as Suk-bae Lee an Auh Keun Ho.

## Intermediate

In the year 2023, three papers were published on seemingly the same topic, and they are completely different. The discussion of LK-99's formulation and superconducting properties looks similar (with different details), but the theories are very unrelated and the authors are even trying to insert their own theories.

It is unlikely that any of these theories are correct, assuming that LK-99 is indeed a normal pressure, normal temperature superconductor. It's only slightly more likely because Hyun-Tak Kim has done something similar before, but it's usually more rare that a group that makes a discovery that contradicts an existing theory has a theoretical explanation readily available.

A possible explanation is that the research group was the only group having the candidate substance and wanted to develop the theory to the point where they could publish it together. As mentioned in the interview, Chair's will was not only the discovery of a normal-pressure, normal-temperature superconductor, but also the establishment of a theory. So they wouldn't want to publish LK-99 before Chair's theory was established. It is also possible that Young-wan Kwon and Hyun-tak Kim participated because they were the few candidates who could accept these conditions.

## Interviews

### Hyun-Tak Kim (New Scientist, 2023-07-26)

https://www.newscientist.com/article/2384782-room-temperature-superconductor-breakthrough-met-with-scepticism/

First interview since the paper was published. Kim is best known among researchers, so an obvious choice.

1. paper 2 was published without the consent of the research group and is highly problematic.
2. Kim is willing to help reproduce and test LK-99 after the paper is published in a peer-reviewed journal. (However, this could be interpreted to mean that he cannot do so before publication).

### Suk-bae Lee (Chosun Biz, 2023-07-27)

https://biz.chosun.com/science-chosun/science/2023/07/27/CYOH5RGWHVDGDAJSJDW5S4SKXE/

First interview with Korean media. Unlike other interviews, he met with reporters in person.

3. Submitted a paper to Nature in 2020, but they rejected it because of the Dias case.
4. demanded to be published in other specialized journals first. So they verified it by domestic journal and posted on arXiv later.
5. submitted a paper to APL Materials.
6. There are several offers for collaboration with overseas researchers.

Note that I did not explain whether the papers posted/submitted in 3/4/5 correspond to papers 1/2/3. We assume that due to the format of the papers.

### Suk-bae Lee (Yonhap, 2023-07-28)

https://www.yna.co.kr/view/AKR20230728146700017

The same person was interviewed by phone this time, with subtle differences from the previous interview.

7. paper 2 was posted without the consent of the research group and has been requested to be removed.
8. Kwon resigned as a director of the company 4 months ago (2023-03?) and is no longer associated with it. (He said the university also cannot contact him)

It is important to note that 7 is the same statement as 1 in Kim Hyun-tak's interview, but different from 4. Given the circumstances, it seems likely that 1 and 7 are true, and that 4 was said in an attempt to make it seem like the research group was not in trouble.

It is not clear what exactly is going on with 8 (especially since Young-wan Kwon went to present at MML 2023), but we can at least assume that there is a conflict between Kwon and the rest of the group, or that they are going in different directions for some internal reason.

### Condensed Matter Theory Center (2023-07-29)

https://twitter.com/condensed_the/status/1684960318718406656

> [...] reliable sources tell us that the authors are willing/eager to share their LK-99 samples with serious experimental groups

Not a direct interview, but a tweet that hints at the situation for research groups. They don't say who the "reliable source" is, but given the context, likely the researchers who requested the collaboration from the Quantum Energy Institute (there were rumors that it was researchers from MIT).

From the context and 2, they were originally going to do everything quietly and then announce it all at once. I don't have a problem with helping after the announcement, but it seems like they didn't want to be stabbed in the back before that, and now that they can't hide anymore, they're trying to be more proactive in their collaboration.

### Conclusion

Based on what we've seen so far and similar cases in the past, it's reasonable to assume that it's unlikely that LK-99 is a room-temperature superconductor, and no judgment can be made until sufficient cross-validation. The fact that LK-99 suddenly became a hot topic, the fact that it was announced by a private company that was shrouded in secrecy, and the poor quality of the published papers make it seem like it dropped out of the sky and was the work of a single attempt.

However, in context, it's worth keeping an eye on this situation for the time being. These people have been interested in this problem for a long time, though they have a non-mainstream theory, also be attempting to develop LK-99 and collaborate with experts in the field to prove their non-mainstream opinion.