Great Country Academician

After obtaining the replica experiment data and superconducting test data of the KL-66 material, Xu Chuan did not disclose it immediately.

It has been confirmed that the Meissner effect does not exist in these three sets of controlled reproduction experiments. Unless the subsequent reproduction experiments made by other laboratory research institutions show completely different results, from this point of view, it is already It is enough to preliminarily confirm that the KL-66 material is not a room temperature superconductor.

However, Xu Chuan felt that since it was going to be done, it should be done perfectly so that it was 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, whether it is the video from South Korea showing strong diamagnetic properties, or the second group of KL-66 material samples in his replica experiment, they all show strong diamagnetic properties and can float.

Explaining the principle of this aspect is enough to kill 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 because of this mechanism that aroused his curiosity.

It has to be said that the strong diamagnetic mechanism exhibited by the KL-66 material developed by South Korea this time does have some problems.

Judging from the material antimagnetic test data of No. 2 KL-66, the reason why it can show the ability of suspension is that some of the polycrystalline ceramic samples reproduced contain soft ferromagnetic components.

This is the core of its ability to levitate under the application of an external magnetic field.

However, Xu Chuan was a little surprised that the soft ferromagnetic components were not saturated when the external magnetic field was added to 5T.

This means that the material has great potential for antimagnetism.

So even if the Meissner effect was not observed in the three sets of replica experiments, he still retains his research interest in this material.

After all, there are still many applications of strong diamagnetism, such as magnetic levitation, medical treatment, motors, etc. If a new strong diamagnetic material can be found, there may be an opportunity 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, maybe he can further increase the critical magnetic field of superconducting materials, and further compress the volume of controllable nuclear fusion reactors.

This is the main reason why he is really interested in this material.

This material may allow him to find a way to miniaturize fusion reactors.

In the laboratory, Xu Chuan hired a researcher to assist him in his work, and conducted antimagnetic tests and structural analysis on the No. 2 KL-66 material.

At the same time, the second wave of replica experiments on KL-66 materials was launched again.

However, unlike the first time, this re-enactment is not to verify the superconductivity of the KL-66 material, but to target its diamagnetic effect.

Xu Chuan needs to figure out what exactly happened during the synthesis process, resulting in a huge improvement in the soft magnetic effect of the polycrystalline ceramic sample in No. 2 KL-66 material, as well as the corresponding crystal structure, atomic substitution, etc. In the end is how to form.

It is also necessary to figure out why the No. 1 and No. 3 KL-66 materials do not have such a strong diamagnetic effect in the same synthesis steps.

Only when these things are known and the mechanism is confirmed, can the next step be carried out.

"Boss, the results of the detailed magnetization measurement report are out."

In the office, Chaili rushed over with a test report.

"Let me see."

Xu Chuan quickly took the test report from the other party, and carefully read it.

In physics, the magnetism of general materials can be divided into several types such as paramagnetism, diamagnetism and ferromagnetism.

For example, ferromagnetic materials are materials that are placed in a magnetic field or lowered below a certain temperature. The materials are magnetized to generate a strong magnetic field and the materials have clear magnetic poles. For example, some materials containing elements such as iron, cobalt and nickel, after magnetization materials can retain ferromagnetism.

For paramagnetic materials, the material is placed in a magnetic field, and the material is magnetized to generate a smaller magnetic field with the same direction as the original magnetic field, and its magnitude is proportional to the original magnetic field, but it will disappear after the external magnetic field is withdrawn.

As for the diamagnetic material, the material is placed in a magnetic field, and the magnetic field generated inside the material is opposite to the direction of the original magnetic field, which will weaken the total magnetic field instead.

Generally speaking, ferromagnetic materials will be attracted by the original magnetic field when placed in a magnetic field, while diamagnetic materials will be repelled by the original magnetic field.

If you want to understand it simply, it means that two magnets of the same polarity are put together, and then you squeeze them hard with your hands.

The greater the force required to make them stick together, the higher the diamagnetism.

Although it is not accurate to say this, it is relatively easy to understand and visualize.

From the test report, the magnetic susceptibility of the No. 2 KL-66 material reaches 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 vacuum is consistent with the original magnetic field.

The magnetic susceptibility of ordinary diamagnetic materials is negative, but very close to zero. For example, water, some organic matter, and a small amount of metal are all common diamagnetic materials.

The magnetic susceptibility of a superconductor is -1, reaching the maximum value of diamagnetism. Significantly different from common diamagnetic materials, it is 100% diamagnetic.

Therefore, superconductors repel external magnetic fields very strongly and can firmly bind the magnetic flux lines, while ordinary diamagnetic materials only slightly repel external magnetic fields.

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The magnetic flux rate of 0.8225, although there is still a certain distance from the magnetic susceptibility of superconducting material-1.

But don't forget that the KL-66 material they synthesized is actually not very pure.

If the purity continues to increase, it is not impossible for the magnetic susceptibility of this material to be infinitely close to that of a superconductor or to be directly full.

"Interesting, when will the electron microscope structure come out?"

Putting down the report in his hand, Xu Chuan looked at Chaisu and asked.

"I'm already doing it, and it will take about 20 minutes." Chaili replied respectfully.

Nodding his head, Xu Chuan said, "Okay, report to me as soon as you finish."

The astonishing magnetic susceptibility did arouse his interest, which also means that even if this material is not a superconductor, it still has great potential in some aspects.

Chaisu 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 eg orbitals for interaction values ​​determined from constrained random phase approximation (cRPA).

But no forced magnetism or orbital symmetry breaking was found in the material's electron-holes.

Whereas in the two insulators using DFT+U: Cu-doped Pb the mechanisms that play a role in the stable insulating state and impurity levels in the band gap 10(PO4)6o and V-doped SrTiO3 doped with transition metals.

So in theory, there are isolated impurity (flat) bands, independent of the doping position. Even under the optimal conditions for superconductivity, the spin and orbital fluctuations are too weak for superconductivity near room temperature.

Because it is almost impossible to exhibit superconductivity at room temperature.

However, if diamagnetism is considered, the situation may be different.

Theoretically, the interstitial gap in the material results in two spin-polarized impurity bands in the same unit cell where dopant types differ.

Whereas weak ferromagnetism is possible due to relatively delocalized 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 deduced silently in his mind, and occasionally used a pen to do calculations on the manuscript paper.

The knowledge of materials science in the mind is integrated with the information in the fields of physics and chemistry.

If anyone has experienced the moment when he used to prove the last step of the NS equation in class, he must be familiar with this state.

However, Xu Chuan was the only one in the office at this time. Under the deduction with all his concentration, he didn't realize that he had returned to the state he dreamed of most today.

It was not until a long time passed, when Chai Li who rushed over with the structural data of the electron microscope, gave a soft cry, that Xu Chuan came back to his senses.

He breathed a sigh of relief from the illusion of a world away, and looked at the time in the lower right corner of the computer, only to realize that nearly half an hour had passed before he knew it.

"Boss, the structural data of the electron microscope is out." Chai Li swallowed and reported, why did he feel like he did something wrong when he obviously did nothing?

Xu Chuan nodded and said, "Just put it here."

"Okay." Quickly put down the test report in his hand, and Chai Li ran away in a hurry. Originally, he still wanted to ask some questions, but suddenly changed his mind.

Sitting at the desk, Xu Chuan closed his eyes and thought about it for a while, before he leaned forward and picked up the electron microscope scanning structure report from the table, and flipped through it.

"Sure enough. At the non-interacting level, KL-66 is an inversion asymmetric Weyl semimetal."

"Weyl nodes with opposite chirality appear at different energies around the time-reversal invariant Γ and A points in the three-dimensional Brillouin zone. The unusual Weyl charge CW = ±2 and passes parallel to the surface of the bulk The two branches of the topologically protected Fermi arc state connect the c-axis."

"That is to say, in the KL-66 material, the spin-orbit coupling of Cu atoms has a crucial impact on the material's energy band structure and electronic properties."

After looking at the scanning structure diagram and related inspection data, Xu Chuan's eyes revealed a look that had already been predicted.

Although the deduction was interrupted by Chaisu, he was not without gains.

Theoretically speaking, he has roughly found the core reason why the KL-66 material has strong magnetism through deduction.

However, whether it is accurate or not still needs to be seen in follow-up experiments.

Perhaps this time, he can make a complete correlation between the strong diamagnetic material and the energy band topology, and then push the strong correlation physics to a whole new level.

PS: There is another chapter in the evening, asking for a monthly pass.