Shulou(Shulou.com)11/24 Report--

The latest development of LK-99, Princeton University Schoop Lab failed, but also put forward a new point of view:

According to the calculation of formation energy, it seems that it is not feasible to doping copper at lead atomic site.

In particular, they mentioned that the synthesized sample crystals are transparent under a magnifying glass.

The team did not observe any signs of superconductivity in magnetic and resistance measurements; the theoretical calculation results show that the doping of copper is unstable and the electronic structure is not conducive to superconductivity and magnetism.

The final conclusion of this 38-page paper supports the results of yesterday's Peking University team paper:

Pb "Cu (PO atmosphere)" (OH) is more likely to be a magnet than a superconductor at room temperature and pressure.

So far, the paper has not been uploaded to arXiv, and just a Google document has attracted a lot of attention. Andrew S. Rosen, who is coming to Princeton as an assistant professor of chemistry and biological engineering, said:

(the extra energy required for copper atoms to replace lead) 13.9 eV, this energy is too high.

As for why some successful cases can be seen according to this conclusion, Prof Michael S Fuhrer, a professor of quantum materials physics, pointed out that the real conclusion of the Princeton team's paper should be that "the structure proposed by the Korean team is not necessarily accurate and may not be the same as the real matter in the experiment."

But Jorrit de Boer, a cryogenic physicist and quantum systems engineer, believes that this is a very detailed paper written by a very famous research team, which is at the top level in the field of complex crystal "growth" and electronic theory.

The paper also contains "the root cause of why lead-copper substitution is highly unlikely to occur with any synthesis method." of course (with the Korean team sample) is not exactly the same crystal, but it seems to be over.

What did the Princeton team say? The Princeton team gave a summary of their research:

The sample is synthesized according to the process described by the Korean team, which is multiphase.

The core material apatite single crystal is separable and transparent. The single crystal X-ray diffraction (SXRD) analysis is consistent with the published sample powder pattern.

According to the calculation of formation energy, it seems that it is not feasible to doping copper at lead atomic site.

In addition, even assuming that the initial copper-doped structure of the Korean team is correct, for a given structure, the theory predicts that the ground state of the material will be magnetic because of the localized flat energy band.

Let's look at the details below.

In the experimental part, the sample of the Princeton team has more impurities than the original LK-99 of the Korean team, but the main phase can be separated.

The components after separation are in good agreement with the previous X-ray diffraction experimental data (black).

The separated powder is transparent under the microscope. Transparency to light means that there is no strong absorption of the electromagnetic field, so it is more likely not to be a conductor.

Next, they calculated the formation energy from scratch and obtained a highly thermodynamically disadvantageous result of the energy required for copper atoms to replace lead (as shown in the following figure).

The team also carried out the ab initio calculation of phonon spectroscopy (Phonon Spectru) and found that there are virtual phonon patterns in both undoped and copper-doped structures, indicating that the structure is unstable.

The tight-binding model (Tight Binding Model) results show that Cu forms a high-density flat region at the Fermi level. According to quantum geometry, it is shown that it is a strong localized state, which is not conducive to the formation of superconductivity and is more likely to lead to magnetism.

The calculation results of the interacting Hamiltonian (Interacting Hamiltonian) also show that the system has a strong electron correlation effect, which is beneficial to the formation of magnetism and disadvantageous to superconductivity.

The three calculations complement each other, and all show that the strong electron correlation effect of the system is obvious, which is not conducive to superconductivity.

In addition, when detecting the copper-doped structure, it is found that a new diffraction peak appears at 15 degrees for all the materials with different structures, and the intensity of the peak varies with the type of anions and the doping position of Cu.

If this peak is ignored, the Cu "doped Pb" Cu (PO doping) O matches the experimental data best, which indicates that there is structural uncertainty of the Cu doping location.

From these simulation results, the author doubts that copper can be orderly doped into the mineral structure of apatite.

After reading the paper, the University of Maryland Quantum Materials Center suggested that the Princeton team follow up to measure the properties of the samples at low temperatures.

The Princeton team said it would consider it in the future.

The Institute of Physics of the Chinese Academy of Sciences also issued a paper to summarize the latest progress of LK-99 reproduction / research at present.

In terms of research, after the paper by the team of Peking University yesterday, the Beijing National Research Center for condensed matter Physics of the Institute of Physics of the Chinese Academy of Sciences also published a paper.

Sharp "superconducting-like transition" and thermal hysteresis behavior were observed in resistivity and magnetic susceptibility, but no zero resistivity lower than the transition temperature was observed.

We believe that the so-called superconducting behavior in LK-99 is probably due to the decrease of resistivity caused by the first-order structure phase transition of Cu'S at about 385K, from β phase to γ phase at low temperature.

In the reproduction experiment, Andrew, an aerospace engineer, rummaged through the 15g sample, but could not find a third fragment with magnetic reaction.

At present, the samples have been handed over to the interdisciplinary team of the University of Southern California for follow-up experiments.

In addition, a Japanese start-up company in the field of flexible printed circuit boards joined the experimental reproduction. Founder Shimizu Shimizu said:

I have all the equipment on hand, although the probability of a result is extremely low and it is worth a try. The time of the follow-up report is uncertain, please don't expect it.

Domestically, the Zhihu account @ Hu Dou has also updated the latest development: three quartz tubes have been put into the furnace, ready to heat up.

The third one changed the recipe slightly as suggested by netizens in the comment area, and said it should be a protracted war.

Looking at the results of the experiments / studies of each team, someone concluded that:

At this stage, any generation of LK-99 is useless, because each team seems to synthesize a different LK-99. The samples directly provided by the Korean team must be thoroughly analyzed.

According to the latest news from the College of William and Mary newspaper TheFlatHat, the South Korean team has sent a batch of LK-99 materials to the College of William and Mary, where one of the authors of the LK-99 paper, Professor Kim Hyun-tak, is expected to arrive this month, when it will conduct analysis with the university team.

Princeton thesis:

Https://drive.google.com/file/d/1ekD2KVV_SUid2wH__o1ODS3hTl1GUFb5/view?pli=1

Paper of Institute of Physics, Chinese Academy of Sciences

Https://arxiv.org/abs/2308.04353

Reference link:

[1] https://twitter.com/SchoopLab/status/1689014160477261825

[2] https://twitter.com/floates0x/status/1689033398294388736

[3] https://news.ycombinator.com/item?id=37055514

[4] https://flathatnews.com/about-flat-hat-news/

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