Chapter 453 It’s so Despairing!

In addition to the news related to manned space flight, Wen Yuanhang also brought another piece of news about the establishment of the Large Intense Particle Collider project.

On Thursday of the first week after the New Year's Day of 2022, the Science Planning Department is preparing to hold a discussion meeting on the construction of a large-scale particle collider belonging to China.

This meeting is a purely internal academic meeting, with only scholars from the high-energy physics and particle physics fields and relevant personnel from the Science and Technology Department participating.

From site selection to budget, to technical details and other aspects, all need to be discussed and confirmed through meetings.

Xu Chuan must participate in this meeting.

Apart from the fact that he proposed the construction of a large-scale particle collider, as a Nobel Prize winner in physics, his opinion is also crucial.

What's more, inert neutrinos, dark matter, dark energy, and mathematical methods for calculating the energy orbits of physical particles are all related to him.

After Wen Yuanhang left, Xu Chuan took his attention back and put it back on his work.

After dealing with some daily emails and related matters, he returned to Nanjing University and took out the manuscript of the previous calculation of KL-66 materials from the drawer of his office.

Since he was going to Beijing for a meeting in a week, the matter of inviting Academician Sun Ze, the deputy chief designer of the lunar exploration project, would be dealt with together at that time.

The mechanism of KL-66 material has been raised to a very high priority for the subsequent research.

The most important thing is that there are not many people who can help him in this regard. It is difficult for him to find someone to cooperate in research in China.

The inversion asymmetric spin-orbit coupling of Cu atoms has an impact on the band structure and electronic properties of the material. The two branches of the Fermi arc state electrons connect the c-axis and break the inversion symmetry theory.

Looking at the data and theories on the manuscript, Xu Chuan fell into deep thought.

The problem of strongly correlated electron system is one of the core issues in today's condensed matter physics.

But when it comes to things in this area, let alone China, there are not many breakthroughs in the world.

More importantly, the basic physical processes involved in the strong correlation phenomena discovered so far are often difficult to accurately describe in the existing physical framework, so this research is extremely difficult to handle through traditional experimental and theoretical methods.

Perhaps Mr. Yang Zhenning is a very good candidate for communication, as his research in condensed matter physics can be said to be world-leading.

But now he is already 99 years old, so Xu Chuan really can't bear to disturb this old man in his later years.

After thinking quietly for a while, Xu Chuan continued writing on the manuscript he had written last time:

[Research on correlation effect and superconductivity in multi-orbital strong correlation system]

"S = (kB/e)ln(ge/gh)"

"Starting from the tightly bound interaction Hamiltonian: [H=i∑jTi, jaii, σaj, σ+i, i′∑j, j′Uii′aiσai′σ′ajσ′aja]

"The second interaction term has a different contribution: [Uii′= Vi, i′→∑i, i′Vii′ inii′], that is, under density-density interaction."

"From a physical point of view, this is because the two Wannier center wave functions must be antisymmetric, and the lowest energy state is the symmetrical arrangement of two spins (and antisymmetric spatial wave functions). When i→j is prohibited or suppressed, that is, the overlap between adjacent orbits is small, Uiii = U/2→ΣiVii′inii dominates, and the Hubbard model can be given. "

"But how to use mathematics to explain the theory in this regard? "

At his desk, Xu Chuan stared at the theory he wrote on the manuscript and frowned.

This is the most troublesome point in the strongly correlated electron system.

"Is it okay to use the site of the Hubbard model?"

Thinking about it, he wrote a new line of formula: [H = Ht+ Hu =-t (a↑a↑+a↓a↓+h.c)]

This is the particle number conservation model. If half-filling (where strange physics occurs) is used, the Hilbert space consists of 6 states, including 2 fully polarized states |↑, ↑> and |↓, ↓> and 4 S=0 states.

Theoretically, the first two states are self-contained. And the Hamiltonian can be in the 4× 4 spaceSz = 0 for diagonalization.

On the manuscript paper, Xu Chuan checked the mathematical formulas and his thoughts.

After a while, he stopped writing.

The Hubbard model is indeed feasible, but it cannot be used in multi-site situations.

And this is obviously not applicable to the mechanism in KL-66.

After replacing the lead point, the Cu atom splits into two Weyl nodes with opposite chirality through the Dirac cone, forming a multi-site effect, which is also the core mechanism of the strong anti-magnetism of KL-66 material and can even float in a strong magnetic field.

"Perhaps, I should change the route and use the Fermi fluid theory to calculate its electricity and magnetism."

Thinking, Xu Chuan changed his mind and started again.

It is extremely difficult to explain an unfamiliar mechanism, and he did not expect to find useful clues within a day or two.

I don't know how long it has been, and a voice came to my ear.

"Professor, your algebraic geometry class is scheduled this afternoon, and the class will start in fifteen minutes."

In the office, the voice of his newly recruited student Rong Xinji rang out.

Hearing the voice, Xu Chuan came back to his senses, nodded, and said, "Okay, I understand."

Out of curiosity, Rong Xinji glanced at the manuscript on Xu Chuan's desk.

This mentor of his sat frowning and studying something almost all afternoon today. He wanted to see what difficult problem his idol was studying again, maybe he would have a chance to take advantage of it.

After all, he is a graduate student after all, and a gold medalist in IMO, so he still has strength!

[S =(kB/e)ln(ge/gh)H=i∑jTi，jaii，σaj，σ+i，i′∑j，j′Uii′aiσai】

[.]

Rong Xinji: ? ? ? ?

What the hell is this?

How come he doesn't even recognize mathematical symbols? ? ?

Before he could move away from the manuscript with difficulty, he couldn't help swallowing his saliva and asked, "Professor, what are you studying?"

Xu Chuan glanced at him and asked with a smile, "Can you understand it?"

Rong Xinji shook his head.

Can he say he understands a ghost?

He is an IMO gold medalist and a mathematics graduate student, but he doesn't even know what the symbols in the formula mean.

No one will believe this if he tells it out, okay?

It's too despairing.

Hearing this, Xu Chuan smiled and said, "It's normal not to understand it. This is not something in the field of pure mathematics."

After a slight pause, he continued to ask, "Do you know the strongly correlated electron system in physics?"

Rong Xinji nodded to this question. Although he is not a physics major, he still knows about the famous thing called strong correlation.

Smiling, Xu Chuan continued, "These on the manuscript are to calculate the relationship between the correlation effect and superconductivity in the multi-orbital strongly correlated system through mathematics."

Hearing this, Rong Xinji was instantly confused again.

Calculate what? ? ? ?

Seeing his student's confused look, Xu Chuan smiled, stood up, patted his shoulder, and said, "Study hard. If you are interested in mathematics and physics, you can read more physics books. You can also choose this as your doctoral direction in the future."

"As for now, it is not a problem you should think about."

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