After getting the replica experimental data and superconducting test data of KL-66 material, Xu Chuan did not make them public immediately.
The Meissner effect has been confirmed not to exist in these three sets of controlled replication experiments. Unless subsequent replication experiments conducted by other laboratory research institutions show completely different results, from this point of view, it has been It is enough to preliminarily confirm that the KL-66 material is not a room temperature superconductor.
However, Xu Chuan felt that since he was going to do it, he should do it perfectly and make it convincing and impeccable.
After confirming that the Meissner effect does not exist, the remaining key point is to find out why this material can have a diamagnetic effect.
After all, both the video sent by South Korea showed strong antimagnetic properties, and the second set of KL-66 material samples in his replica experiment showed strong antimagnetic properties and were able to float.
Explaining the principle in this regard is enough to hammer down the room temperature superconducting properties of this new material.
Of course, the reason why he wants to study the mechanism in this area is not just because he wants to make it perfect. It was this mechanism that aroused his curiosity.
It has to be said that there are indeed some problems with the strong antimagnetic mechanism displayed by the KL-66 material developed by South Korea this time.
Judging from the material antimagnetic testing data of No. 2 KL-66, the reason why it can demonstrate the ability to levitate is that some of the polycrystalline ceramic samples reproduced contain soft ferromagnetic components.
This is the core that allows it to levitate under the application of an external magnetic field.
However, what surprised Xu Chuan was that when the external magnetic field was added to 5T, this soft ferromagnetic component was not saturated.
This means that this material has huge potential for diamagnetic properties.
Therefore, even if the Meissner effect was not observed in the three sets of replica experiments, he still retained his interest in researching this material.
After all, there are still many application fields for strong diamagnetism, such as magnetic levitation, medical treatment, motors, etc. If a new strong diamagnetic material can be found, there may be a chance to replace the expensive superconducting materials originally needed in some fields.
Of course, what interests him more is the principle behind this mechanism.
If the mechanism behind this diamagnetism can be found and applied to the field of real superconducting materials, it may be possible to further increase the critical magnetic field of superconducting materials and further compress the volume of controllable fusion reactors.
That was the main reason why he was really interested in this material.
This material may allow him to find a way to miniaturize fusion reactors.
In the laboratory, Xu Chuan found a researcher to assist him in his work, and conducted targeted diamagnetic testing and structural analysis of the No. 2 KL-66 material.
At the same time, the second wave of reproduction experiments on KL-66 materials was also launched again.
However, unlike the first time, this re-engraving is not to verify the superconductivity of KL-66 material, but to focus on its diamagnetic effect.
Xu Chuan needs to figure out what happened during the synthesis process that led to the huge improvement in the soft magnetic effect of the polycrystalline ceramic sample in the No. 2 KL-66 material, as well as the corresponding crystal structure, atomic substitution, etc. How was it formed?
It is also necessary to understand why the No. 1 and No. 3 KL-66 materials did not exhibit such a strong diamagnetic effect in the same synthesis steps.
Only by knowing these things and confirming the mechanism can we start the next step of work.
"Boss, the detailed magnetization measurement report results are out."
In the office, Chai Su hurried over with a test report.
"Let me see."
Xu Chuan quickly took the test report from the other party and read it carefully.
In physics, the magnetism of general materials can be divided into several types such as paramagnetism, diamagnetism and ferromagnetism.
For example, ferromagnetic materials are placed in a magnetic field or dropped below a certain temperature. The material is magnetized, generating a strong magnetic field and the material has clear magnetic poles. For example, some materials containing elements such as iron, cobalt, nickel, etc., after magnetization The material can retain ferromagnetism.
For paramagnetic materials, when the material is placed in a magnetic field, the material is magnetized to produce a smaller magnetic field with the same direction as the original magnetic field and a size proportional to the original magnetic field, but it will disappear after the external magnetic field is removed.
As for diamagnetic materials, the material is placed in a magnetic field. The magnetic field generated inside the material is in the opposite direction to the original magnetic field, which will weaken the overall magnetic field.
Generally speaking, ferromagnetic materials placed in a magnetic field will be attracted by the original magnetic field, while diamagnetic materials will be repelled by the original magnetic field.
If you want to understand it simply, diamagnetism is when two magnets of the same pole are put together, and then you squeeze them with your hands.
The greater the force required to hold them together, the higher the resistance to magnetism.
Although this is not accurate, it is relatively easy to understand and vivid.
Judging from the test report, the magnetic susceptibility of No. 2 KL-66 material reached an astonishing -0.8225.
This value is already very high for a non-superconducting material.
For magnetism, the magnetic susceptibility of vacuum is 1, which means that the magnetic field in the vacuum is consistent with the original magnetic field.
The magnetic susceptibility of ordinary diamagnetic materials is negative, but very close to 0. For example, water, some organic matter, a small amount of metal, etc. are all common diamagnetic materials. The magnetic susceptibility of superconductors is -1, reaching the maximum value of diamagnetism. Significantly different from ordinary diamagnetic materials, it is 100% diamagnetic.
Therefore, superconductors repel external magnetic fields very strongly and can tightly bind magnetic flux lines, while ordinary diamagnetic materials only repel external magnetic fields slightly.
-
The magnetic flux rate is 0.8225, although it is still far away from the magnetic susceptibility of -1 of superconducting materials.
But don’t forget, the KL-66 material they synthesized is actually not very pure.
If the purity continues to be improved, it is not impossible that the magnetic susceptibility of this material is infinitely close to that of a superconductor, or that it can be directly reached.
"Interesting, when will the electron microscope structure be released?"
Putting down the report in his hand, Xu Chuan looked at Chai Su and asked.
"It's already being done. It will probably take about twenty minutes." Chai Su replied respectfully.
Nodding, Xu Chuan said: "Okay, report to me as soon as you are done."
The astonishing magnetic susceptibility really aroused his interest, and it also means that even if this material is not a superconductor, it still has great potential in some aspects.
Chai Su nodded, turned around and walked out of the office, closing the door gently.
Sitting at his desk, Xu Chuan began to think.
From previous tests on the KL-66 material, he passed the dual-band model of copper to determine the orbital interaction values from the constrained random phase approximation (cRPA).
But no forced magnetic or orbital symmetry breaking was found in the material's electron holes.
While the mechanisms that play a role in stabilizing the insulating state and the impurity levels in the bandgap are found in the two insulators using DFT+U:Cu-doped Pb 10(PO4)6o and V-doped SrTiO3 doped transition metals.
So theoretically, having isolated impurity (flat) bands has nothing to do with the doping position. Even under the best conditions for superconductivity, spin and orbital fluctuations are too weak for superconductivity near room temperature.
Because it is almost impossible to show superconductivity at room temperature.
However, if we consider diamagnetism, the situation may be different.
Theoretically, when doping different types of sites in the same unit cell, gaps in the material would result in two spin-polarized impurity bands.
And weak ferromagnetism is possible due to relatively non-localized unpaired spins in the valence band.
Further work should consider the possibility of further changes in stoichiometry, different doping positions, supercell effects and quantification of magnetic exchange interactions.
In the office, Xu Chuan silently carried out deductions in his mind, and from time to time he would take a pen to do calculations on the manuscript paper.
The materials knowledge in the mind is integrated with information in the fields of physics and chemistry.
If anyone has experienced the last step of proving the NS equation in class, he will be familiar with this state.
However, Xu Chuan was the only one in the office at this moment. With all his concentration on the deduction, he did not realize that he had returned to the state he dreamed of most today.
It wasn't until a long time passed and Chai Su, who came over with the electron microscope structural data, shouted softly that Xu Chuan came back to his senses.
The illusion of a world away made him let out a long sigh of relief. He looked at the time in the lower right corner of the computer and realized that nearly half an hour had passed without him realizing it.
"Boss, the electron microscopy structural data is out." Chai Su swallowed his saliva and reported. Why did he feel as if he had done something wrong when he had done nothing?
Xu Chuan nodded and said, "Just put it here."
"Okay." He quickly put down the test report in his hand, and Chai Su ran away quickly. Originally he still had some questions to ask, but suddenly changed his mind.
Sitting at his desk, Xu Chuan closed his eyes and thought about it for a while. After a while, he leaned forward and picked up the electron microscope scanning structure report from the desk and started to read through it.
"Sure enough. At the non-interaction level, KL-66 is an inversion asymmetric Weyl semimetal material."
"Weyl nodes with opposite chirality appear at different energies near the time reversal invariant Γ and A at points in the three-dimensional Brillouin zone. The unusual Weyl charge CW=±2 and passes parallel to the surface of the body The two branches of the topologically protected Fermi arc state connect the c-axis ”
"In other words, in the KL-66 material, the spin-orbit coupling of Cu atoms has a crucial impact on the energy band structure and electronic properties of the material."
After looking at the scanned structure diagram and related inspection data, Xu Chuan's eyes showed a hint of anticipation.
Although his derivation was interrupted by Chai Su, he was not without gains.
Theoretically speaking, he has roughly found the core reason why KL-66 material has strong magnetism through deduction.
However, whether it is accurate or not depends on subsequent experiments.
Perhaps this time, he can make a complete correlation between strong diamagnetic materials and energy band topology, and then push strong correlation physics to a whole new level.
PS: There will be another chapter tonight, please vote for me.