With the two papers Xu Chuan posted on arxiv, discussions about KL-66 materials once again set off a wave on the Internet.
But this is almost the last flashback.
After all, the magnetic levitation mechanism of KL-66 has been explained accordingly. Unless a subsequent research team can observe the Meissner effect on the reproduced KL-66 material, it is basically impossible for another turning point to occur.
In the next few days, scientific research teams from various countries announced the replica results, which can be regarded as comprehensive confirmation that LK-66 is not a superconductor.
Even South Korea's own scientific research institution, the South Korean Superconductivity and Cryogenics Society, publicly announced that "there have been no results confirming that the KL-66 material is superconducting."
Although it is a pity that a new path has not been found in the field of materials, this is not the first time that such news has appeared in the field of room temperature superconductivity.
Xu Chuan didn't pay attention to the turn of news from the outside world. At this moment, he had returned to Nanda and was doing derivation and research in his office.
Although calculations and replica experiments have confirmed that KL-66 is not a room temperature superconductor, his research on it is not a waste of time.
Instead, he discovered a novel atomic doping structure in this diamagnetic material.
The inversion asymmetric Cu atom spin-orbit coupling has a significant impact on the material band structure and electronic properties. The core is that the two branches of the Fermi arc state electrons connect the c-axis and break the inversion symmetry.
This in turn causes the Dirac cone to split into two Weyl nodes with opposite chirality, leading to non-trivial quantum phenomena.
This is the core mechanism why KL-66 material has strong diamagnetic properties and can even float in a strong magnetic field.
It is also a phenomenon that has never been discovered in the physics and materials science circles.
What he explored was the secret behind this phenomenon.
"Professor, you are back."
In the office, Cai Peng walked in and saw Xu Chuan sitting behind the desk at a glance, and shouted in surprise.
If you ask a question on βhu: "What is it like to have a mentor who is a Nobel Prize winner?"
He, Cai Peng, is definitely qualified to answer!
First of all, what is certain is that it is definitely good to learn from such a top expert.
However, what is often disappointing is that mentors of this level are basically not in the office most of the time, either participating in national projects or busy with their own things.
Just like him, after following his mentor for more than two years, he has only met his mentor in person, which can be said to be only a handful.
For students, they are like left-behind children most of the time. Learning everything depends on their own initiative or looking for their senior brothers and sisters.
It would be even worse if the tutor you meet has high requirements for graduation.
Fortunately, he still has a senior brother. Although Gu Bing has graduated and left, he is still a mathematics professor at Nanjing University.
If he encounters some problems, he can still go to this senior brother for help.
But relatively speaking, he studied differential equations, while Gu Bing studied algebraic topology and analytic geometry. There was no way to guide him a lot of the time.
In this case, all he could do was send the question to Xu Chuan through Weixin or email.
Although you can basically receive answers, the efficiency of asking questions through these methods is definitely much lower than asking questions face to face.
Of course, he can understand this situation, after all, his mentor is a bit too 'beta'.
But understanding is understanding, but being unable to see anyone all year round makes him feel like a left-behind child, and he feels miserable.
Hearing the voice, Xu Chuan looked up, nodded with a smile, and asked: "How did you do with the question I asked you before?"
When he came back last time, he wrote a question to this student to check his skills in the past two years and make a targeted course arrangement for him in the future.
However, it was delayed for a while due to the KL-66 material issue in South Korea. The three days must have passed as originally mentioned.
Cai Peng nodded, walked quickly to his seat, found the manuscript paper from the drawer, handed it to Xu Chuan respectfully, and said: "The top stack is my thoughts in the past three days, and the bottom part is what I have been thinking about these days. Some ideas.”
In fact, almost ten days have passed since I got this question.
He has been studying the problems on the manuscript paper for more than ten days, but he has not solved it, but he must still have some ideas and thoughts.
Xu Chuan nodded, reached out to take the manuscript paper, and began to read it carefully.
"The foundation is not bad. There has been progress in the past two years." After reading the answer sheet, Xu Chuan said with a smile: "But you have made a lot of detours in some aspects."
As he spoke, he stood up and dragged out a blackboard from the corner of the office. He wrote and pointed: "For example, when solving this module, you used the Gaussian elimination method to make the augmented matrix (A|b) into the elementary form. The rows are transformed into a ladder matrix and then processed. ”
"This method is correct, but don't you think it's a little too complicated?"
Looking at the calculations on the blackboard, Cai Peng scratched his head and said, "Are you okay? I think the Gaussian elimination method should be very suitable to apply here."
Xu Chuan smiled and said: "Then do you remember iteration?"
Cai Peng thought for a moment, his eyes suddenly brightened, and he blurted out: "Gauss-Seidel iteration!"
Xu Chuan smiled and nodded, saying: "Yes, when the coefficient matrix A is strictly diagonally dominant or symmetrically positive definite, the Gauss-Seidel iteration must converge. Starting from this aspect, it will be better than the Gaussian elimination method you used. Easier. ”
After a slight pause, he continued: "Solving a system of linear algebraic equations is one of the most basic problems in scientific and engineering calculations. The vast majority of computing problems ultimately boil down to the solution of a system of linear algebraic equations."
"The main difficulty in solving large-scale linear equations lies in its workload. How to reduce its workload is the key you should think about."
"Of course, there is also my negligence here. I really haven't taught you anything in the past two years. But I should be in the office in the next few months and can teach you well."
In the office, Xu Chuan picked out some questions and gave guidance on Cai Peng's answer sheet.
Perhaps because of his own experience, whether in his previous life or in this life, he has learned more by himself. Therefore, he also tends to be free-spirited towards the few students he teaches.
However, this approach is not suitable for everyone. And even if you are freeing up, you still need to teach some core theories and thinking methods, otherwise sooner or later you will go astray or fail to understand the core.
After less than half an hour, Xu Chuan stopped and said, "Let's stop here today. You can absorb and digest what I'm talking about in the past two days."
"In addition, I will list a few books. You can read them carefully in the past two months and make up for them. You are still lacking a lot in some knowledge points and need to learn."
While talking, he erased the calculations on the blackboard, thought for a while and wrote: "Elementary Differential Equations and Boundary Value Problems" "Theory of Special Functions" "Numerical Solutions of Differential Equations" "Mathematical Methods in Physics and Engineering" "." After listing six or seven books, he threw the chalk in his hand into the chalk box, clapped his hands, and said: "That's it for the time being. I'll give you three months to study. If you have any questions in the meantime, you can always ask me. I will test your learning results in three months.”
Looking at the six books neatly listed on the blackboard, Cai Peng couldn't help but swallow a breath of air.
Six books, three months, an average of two books a month!
Boss! This is not an online novel, it is a mathematics textbook!
Suddenly, he remembered what senior brother Gu Bing had said to him before: "Learning from your instructor, liver explosion is a necessary skill!"
On the first day when the instructor came back to teach him, he realized what it meant to be a liver-exploding person and it was a necessary skill.
After letting Cai Peng go to school on his own, Xu Chuan sat back at his desk again.
Start thinking again about the possibility of a complete correlation between strong diamagnetic materials and energy band topology.
The problem of strongly correlated electron systems is one of the core issues in condensed matter physics today.
In materials such as complex transition metal oxides (TMOs), due to strong electron-phonon or electron-electron coupling, the collective behavior of system electrons determines its macroscopic properties, and the simple superposition of single electron kinetic energy no longer plays a dominant role.
As external conditions such as temperature and magnetic field change, the material's lattice structure, electronic structure, spin arrangement and other order parameters become entangled with each other, resulting in an extremely rich phase diagram structure.
It then displays macroscopic quantum phenomena such as high-temperature superconductivity and giant magnetoresistance, giving the material new properties with great application value.
There is no doubt that this new phenomenon discovered in the KL-66 material belongs to a strong electronic correlation system.
But it is quite troublesome to integrate this system into mathematical language and explain it.
After thinking for a while, Xu Chuan took out a stack of manuscript paper from the drawer.
[Research on correlation effects and superconductivity in multi-orbital strongly correlated systems]
“S=(kB/e)ln(ge/gh)”
As soon as he wrote a title, before he could develop it further, there was a knock on the office door.
"Please come in." Xu Chuan responded, and the person who came to see him was Tan Shaoyuan, the new president of Nanjing University.
"Academician Xu, regarding what you said about recruiting students last time, I have already asked someone to do a preliminary screening. Here is the list. Take a look."
After Tan Shaoyuan said hello with a smile, he handed over the list materials in his hand.
Xu Chuan took the list and said with a smile: "Thank you, but for this kind of thing, just arrange for an assistant or secretary to come over. Please ask the principal to deliver it in person."
Tan Shaoyuan smiled and said: "I'm just dropping by, what's the trouble?"
After a slight pause, he continued: "When I come here this time, in addition to the list, there is one more thing I want to ask."
"Well, please tell me."
Tan Shaoyuan coughed slightly and said: "Academician Xu, you said when you were teaching last time that you were going to open a course on computational materials science here at NTU. I want to ask about this."
A Nobel Prize winner, and the scholar in front of him who is known as the father of controllable nuclear fusion. Courses offered by such top experts will be greatly criticized no matter which country or university they are placed in. Welcome and attract countless talents.
Putting aside these things, for schools that offer this course, it is definitely a good thing to expand the school's academic atmosphere and international reputation.
Therefore, more than ten days ago, after Xu Chuan finished the class, he came to visit with concern.
However, Xu Chuan had already left Nanda at that time and went to the Sichuan-Hai Institute of Materials to do experiments. He did not come back until today. But this time, he couldn't wait to come to the door and wanted to ask about the situation.
The leadership position of Nanjing University is a very prestigious position in today's academic world.
After all, here is the number one academic person in China and even the world. As long as this person is still at NTU and sits there for a few years, he will be able to achieve various results.
Hearing this question, Xu Chuan suddenly remembered what he had said in class before.
Smiling, he said: "I had this idea before. After all, I have some understanding in the field of computational materials science, and I wanted to see if I could spread it."
Hearing this, Tan Shaoyuan quickly said: "Then I will make arrangements here and get the relevant work done as soon as possible."
Xu Chuan said with a smile: "There is no need to rush this. Although I have ideas in this regard, my time here is not stable. If I open a subject specifically, I am worried that I will miss the students who apply for this subject."
After thinking for a while, he spoke again: "Well, let's not treat the computational materials mathematics course I teach as a major or minor. Let's open a special course on technological innovation here at Nanjing University."
"I hold classes here from time to time and give advance notice, and then interested students can come and listen. When the situation here becomes more stable, I will offer special courses."
He did originally offer a course on computational materials science, but when he was studying KL-66 materials, he accidentally discovered something in a strongly correlated system.
Later, during the research process, it was discovered that it seemed to promote the miniaturization of controllable nuclear fusion devices, so the idea of starting a class was cancelled.
After all, compared with the importance of miniaturized and controllable nuclear fusion reactors, setting up computational materials courses is dispensable.
Hearing this, Tan Shaoyuan smiled and nodded, saying: "Yes, Academician Xu, you can arrange it. If you need to start classes, you can tell me at any time and I will help arrange it."
Xu Chuan smiled and said: "No problem."
"Then don't disturb Academician Xu's work."
Tan Shaoyuan left the office with a smile, while Xu Chuan picked up the list materials in his hand and read them.
"Professor, do you want to recruit new students?"
In the office, Cai Peng, who had been silent for the whole time, looked over curiously after Principal Tan left.
Xu Chuan nodded and said: "Well, I will take advantage of the relatively leisure time in the past few months to take a few students with me."
Cai Peng asked excitedly: "Then I will be the senior brother from now on?"
Xu Chuan glanced at him and said, "You'd better think about how to graduate."
Cai Peng: "\φ(゜▽゜*)\"