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https://pubpeer.com/publications/82AF24DF343C16341B42CF36B22FA4




https://pubpeer.com/publications/82AF24DF343C16341B42CF36B22FA4

PubPeer - The First Room-Temperature Ambient-Pressure SuperconductorPubPeer - The First Room-Temperature Ambient-Pressure Superconductorpubpeer.com


#1 Łukasz Bugyi 

Is this too good to be true? I am not material scientist, so I would be very grateful for remarks from someone in the field.

Is the break of superconductivity with current above certain temperature normal in superconductors?

Is the current at which it happens defined by inner structure of the material, or would changing the i.e. conductor cross-section increase this value?

What are the key values to be met for this material to be used in real-world applications?




#2 Anthurium parasiticum commented July 2023

Translated from German:

Source: https://blog.fefe.de/?ts=9a3f8740

I work in the field, and this morning we discussed the preprint a bit within the research group. In short, we don't believe a word of it:

Fig. 1(a) and (c) are not credible. Normally, it should look like this: https://www.researchgate.net/profile/Matthias-Graf-4/publication/233871395/figure/fig5/AS:668845236826120@1536476539728/color-online-a-IV-curves-at-several-representative-magnetic-fields-Three-different.png Notice the gradual increase at low currents; this effect is expected, especially with magnetic fields.

Even Fig. 1(d) can't be correct. At Tc ~ 400K, the Meissner effect would displace a much stronger field than 10 Oe = 1 mT. This means the distinction between FC (field cooled) and ZFC (zero-field cooled) should not be so pronounced. It should look more like this: https://www.researchgate.net/publication/370037045/figure/fig1/AS:11431281152878176@1682210458059/Meissner-effect-in-TiZr-at-three-different-applied-fields-Note-that-in-SI-units-a.ppm

What the authors might mean is that they are outside the Meissner regime, which can occur at higher magnetic fields (Type II superconductors). That would look like this: https://www.europhysicsnews.org/images/stories/hl/472/Guo.jpg

In this case, however, the temperature dependence does not match the critical currents in Fig. 1(a) and (c).

Also, the fact that ALL values in Fig. 1(d) are negative is extremely unusual, although one could possibly argue for it.

The dataset in Fig. 4(b) is also interesting. It's very unusual for the heat capacity to decrease again at high temperatures. That can happen at low temperatures, but not so much at high temperatures.

I am very familiar with the described experimental setup and the cryostat. There is no reasonable explanation why the authors did not measure at higher temperatures to show that the behavior above Tc ~ 400K is significantly different. For example, a temperature dependence of the resistance would have been essential.

Overall, the paper is very poorly written. The data is not adequately discussed, the explanations are lacking, and the cited works are rather, let's say, scarce. This doesn't inspire confidence in what the authors claim to have measured and observed.

My personal suspicion is that the authors measured an insulator, so no current flowed, and thus no voltage occurred (4-point measurement). This makes it look like a superconductor. However, if the current is increased (i.e., the applied voltage), it could lead to breakdowns, and a current starts to flow, which would explain the abrupt increase.

You have no idea how much joy it brings me to have an expert in the audience who can explain things to me regarding complicated topics. In this case, greetings and thanks to the Max Planck Institute for Solid State Research.


#3 Łukasz Bugyi commented July 2023

Hmm, regarding the insulator theory, they indicated on 1a that there is up to 300mA of current without voltage drop, how do You see this happen with insulator?

I absolutely agree that the quality of the paper is astonishingly poor.

Do You think it is possible they got a sample which is partially (spatially) superconducting? Could this explain the weird behavior?



#4 Gaultheria mucronata commented July 2023

I am not able to judge the scientific content of the preprint, but the address given for the research centre where the research is supposed to have taken place [Quantum Energy Research Centre, Inc., (Q-centre, Inc.), B1, 46-24, Songi-ro 23 gil, Songpa-gu, Seoul 05822, Korea; i.e., 서울특별시 송파구 송이로23길 46-24] would be the basement unit of this mixed-use residential building (see the attached Street View picture from KakaoMap, which sits right across from a nice children's plauground), which certainly does seem unusual.

(밑에 건물사진 첨부했음)


#5 Pityokteines curvidens commented July 2023

I will let others who are more qualified (i.e. physicists) to comment on the physics/superconductivity aspects of this preprint. Here I will provide a chemist's perspective on the sythesis and structural characterization of the purported LK-99 material.

  1. The claimed synthesis can be described by the following reactions:

PbO + PbSO4 -> Pb2(SO4)O (725 °C, 24 h) 3Cu + P -> Cu3P (550 °C, 48 h, vacuum) Cu3P + Pb2(SO4)O -> Pb10-xCux(PO4)6O, x=0.9-1.0 + Cu2S (minor impurity) (925 °C, 10 h, vacuum)

It is immediately apparent that the stoichiometry of the last reaction is impossible to balance. Moreover, the claimed chemistry is highly unusual and lacks precedent. The authors contend that copper phosphide quantitatively reduces sulfate to sulfide while selectively yielding phosphate as the only oxidation product. However, this exchange of sulfate/phosphate based on known chemistry principles seems implausible. The only reference the authors provide in the synthesis section is this:

K. K. O. S. H. Hwang, C. K. Lee, C. M. Lee, D. W. Kim, A Study on Color in Apatite with the Addition of Transition Elements. Journal of the Korean Ceramic Society 23, 43-49 (1986).

While it is in Korean, it is clear that this paper does not claim a similar sulfate/phosphide -> sulfide/phosphate exchange.

Even if we consider the authors' proposed chemistry, it is unlikely that the final phase can be a pure compound. If the superconducting phase is the Cu-doped lead apatite, there must also be a second, copper-rich phase. This second phase cannot be a mere trace compound.

  1. The purported LK-99 material has been characterized by XPS and PXRD.

The authors claim that "he results of LK-99 matched with the QualX2.0 software(27) and proved by simulated data using VESTA software(28)". However, relying solely on a card match to a noisy and contaminated powder diffractogram does not constitute proof of the structure. Furthermore, considering the stoichiometry issue in the synthesis, the matching diffractogram in Fig. 2 could be seen as a liability rather than a validation. The presence of Cu2S peaks highlighted by the authors does not account for all the copper that should be present in the material. Unfortunately, the authors do not provide the actual PXRD data set, making it impossible to evaluate their analysis using the low-res Fig. 2. Additionally, the precision and accuracy claimed by the authors in their extended structural arguments based on PXRD, with reported spacings to 5 significant digits, are unrealistic for the type of PXRD experiment described.

Regarding XPS, the authors fail to report the survey spectrum, which is crucial for any elemental composition argument. The high-resolution data provided are insufficient to support their structural claims and appear suspicious. For instance, the similarity in noise profiles for purported P 2P peaks in Fig. S1(a) and S1(b) is highly unlikely in real experimental data. Furthermore, the subpeaks in other figures lack explanation (e.g., the identification of the 4 oxygen species in the O 1s peaks). The authors attempt to discuss minute changes in chemical shifts, but such small variations are often attributed to noise, which is evident in their data. The discussion of these XPS results indicates that the authors may not be experts in XPS.

Finally, the authors measured heat capacity of their material. However, contrary to their claim, this data does not provide meaningful insights into the material's structure.

  1. Although not explicitly stated, the paper seems to suggest that the authors deliberately designed the target crystal structure, which conveniently turned out to be a superconductor based on the loosely defined "lattice distortion" hypothesis.

Despite significant advances in material synthesis over the past century, achieving atomic precision to manipulate material structures as claimed here remains far from reality. It is improbable for any chemist to "design" a reaction that precisely reduces the lattice volume by exactly 0.48%. If the authors claimed to have serendipitously stumbled upon a room-temperature superconductor, their claim would have been way more believable.

The reported synthesis appears to reflect physicists attempting chemistry as they envision it. Mixing things together, subjecting them to rather extreme temperatures (under high vacuum, naturally), and expecting all atoms to connect flawlessly in "triangles." The interchange between phosphide and phosphate seems almost trivialized. If I were assigned the task of synthesizing a Cu-doped lead phosphate phase, the proposed 925 °C synthesis with Cu3P and Pb2(SO4)O would not have been among the options. There are more plausible methods available, such as hydrothermal pathways or ion exchange, that could achieve this goal with greater feasibility.

In summary: I wish this report was credible, but I don't think it is.



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