Source | Qubit | Public Account QbitAI
Is the first successful reappearance of South Korea's "room temperature and atmospheric pressure superconductor material" ? !
Teachers and students from the School of Materials Science and Technology, Huazhong University of Science and Technology, just announced on the first video at Station B:
They have synthesized LK-99 crystals that can be magnetically levitated . The crystal levitation angle is larger than the sample magnetic levitation angle obtained by Sukbae Lee et al., and it is expected to realize the true non-contact superconducting magnetic levitation.
Judging from the released video, under the microscope, this "small black spot" keeps falling or standing up as the NdFeB magnet approaches and moves away, regardless of whether the S pole or the N pole is effective, that is, the repulsion and magnetic poles Regardless, exhibits diamagnetism .
As soon as the news came out, it immediately attracted hundreds of thousands of netizens to watch. Although the team stated that it had not yet tested the resistance to prove superconductivity, the screen was full of "witness to history".
At the same time, foreign netizens also quickly set their sights on Station B.
"For the first time to verify the synthesis of LK-99 crystals that can be magnetically levitated"
The news was released by the UP master of station B "Guanshankou Man Technician".
The introduction on the homepage shows that this UP is from Huazhong University of Science and Technology. The LK-99 paper was put into reproduction work as soon as it came out, but the previous experimental results did not show such a strong diamagnetism.
Today he finally announced the initial success, and also revealed that his team is led by Professor Chang Haixin from the School of Materials Science and Technology of Huazhong University of Science and Technology, and the members are postdoctoral fellow Wu Hao and doctoral student Yang Li.
In the video, the LK-99 crystal they synthesized is a small black spot pointed by the toothpick below, with a diameter of only tens of microns.
After being magnified by a microscope, it is barely clear:
Then, a NdFeB magnet was placed under it and the reaction was observed.
We can see that as the magnet below approaches, the crystal quickly stands up (partially suspended), and then falls quickly after moving away:
After swapping the poles, the same effect remains:
As netizens said, through this video, we can see that LK99 is diamagnetic, "It shows that the Korean paper is really not lying."
, It is the level that can shout WC.
Next, superconductivity and flux quantization are properties to be verified.
Netizens expressed excitedly that whether the subsequent experiments are successful or not is a major breakthrough.
Because "even if there is only diamagnetism, it is a huge discovery. After all, materials with such strong diamagnetism at room temperature are very rare."
Next, the team will indeed do resistance measurements to verify superconductivity, UP said.
But the bad news is that since there is only one piece of the sample , in order to prevent it from being damaged, we have to wait for the next batch to come out before starting.
Now someone said: I understand the truth, but I am really in a hurry.
Computer simulation joins the ranks of verification work
In the process of the initial reappearance of Huazhong University of Science and Technology, new progress has been made in the verification of relevant theories.
Just this morning, the message read:
Computer simulations conducted by the Lawrence Berkeley National Laboratory (LBNL) in the United States theoretically support the conclusion that this material has room temperature superconductivity.
They calculated the valence electron bands at the Fermi level in the VASP software according to the density functional theory (DFT) method.
Finally, it was found that the substitution of copper resulted in an extremely narrow (bandwidth of only 130meV) flat valence band at the Fermi level .
This flat band is related to the electronic density of state , a key parameter of superconductivity , and is an important feature for realizing high-temperature superconductivity .
The Fermi band is an energy benchmark, and the more electrons in this band, the higher the superconducting temperature .
However, the author also mentioned in the paper that it is difficult to actually synthesize this material.
In addition, some foreign netizens questioned this:
Why use apatite containing hydroxyl groups? Wouldn't such a group have an effect on the lone pair of electrons?
Domestically, the Shenyang National Laboratory of Materials Science, Chinese Academy of Sciences also performed calculations.
Starting from first principles, the researchers calculated the electronic structure of LK-99 using the ab initio method.
The results show that near the Fermi level, there are also flat bands .
The lead apatite structure, which is not replaced by copper atoms, is insulating.
However, the laboratory did not give a clear conclusion on whether LK-99 has superconducting properties.
But also in China, Beihang’s experiment gave the opposite answer:
LK-99 not only does not have room temperature superconductivity, but exhibits the characteristics of semiconductors.
Beihang's experiments show that the resistivity of LK-99 at room temperature is 1.94×10^4Ω·cm.
What is this concept? At room temperature, with the unit of Ω·cm, the resistivity of general metals is on the order of 10 to the power of -4 to -2.
For a conductor of the same length and cross-section, the greater the resistivity, the worse the conductivity .
In other words, according to this experimental result, the conductivity of LK-99 is not as good as that of ordinary metals .
However, X-ray diffraction (XRD) results show that the structure of the product synthesized by the Beihang team is consistent with that of the Korean team .
One More Thing
While the world is in full swing to reproduce LK-99, the Korean team's paper is also republished.
However, the substantive modification is only this one picture, and it only splits the two sets of lines in the same coordinate system.
In addition to LK-99, the US company Taj Quantum also proposed another superconducting material.
This is a graphene foam material published as a patent (patent number: US-11710584-B2).
In short, the smoke brought by LK-99 has not dissipated, and I don’t know where the bullets are flying now...
Video address:
https://www.bilibili.com/video/BV14p4y1V7kS
American LBNL paper:
https://arxiv.org/pdf/2307.16892.pdf
Shenyang Materials Laboratory paper:
https://arxiv.org/pdf/2307.16040 .pdf
Beihang paper:
https://arxiv.org/pdf/2307.16802.pdf
Taj Quantum patent:
https://image-ppubs.uspto.gov/dirsearch-public/print/downloadPdf/11710584