Chapter 340 The Mechanism of High-Temperature Superconductivity and Strong Correlation Effect

In the office, Xu Chuan fell into deep thought.

On the side, Fan Pengyue and Song Wenbai did not dare to interrupt the boss's thinking, and could only wait quietly.

After sorting out the thoughts in his mind, Xu Chuan raised his head, looked at Song Wenbai with shining eyes, and said:

"Professor Song, in the next period of time, you and your team will temporarily stop the research on copper-carbon-silver composite materials, and turn to analyze the ultra-low temperature superconducting copper-carbon-silver composite materials you have previously studied."

"I need more information and analysis data for this material!"

Hearing this, Song Wenbai was stunned for a moment, and then quickly nodded and replied: "It's no problem to turn from research to analysis, but for the analysis of materials, our institute may still lack some equipment."

"For example, we don't have a pyrolysis chromatograph or an inductively coupled plasma emission spectrometer for characterization and structural analysis. Without these equipment, the analyzed data is not perfect."

Xu Chuan: "That's no problem. Mr. Fan will communicate with you about the relevant equipment. Buy what you need. Equipment is not something you buy just for this one time."

Fan Pengyue nodded and said: "The institute has only been expanded for a short time. Some equipment has not been purchased yet, but it has been arranged in the procurement plan. It's just that the priority was lower before. Now that you need it, you can also purchase it in advance."

Xu Chuan: "If it takes a long time to buy a new one, you can try to buy a second-hand one from other domestic laboratories. It doesn't matter if it's a little more expensive. I need to get the data as soon as possible."

In the conference room, Xu Chuan asked some more questions about the experimental data of the ultra-low temperature superconducting copper-carbon-silver composite material, and left the Chuanhai Materials Research Institute with part of the data.

Back to the villa, he inserted the USB flash drive in his hand into the computer, took out a stack of manuscript paper from the drawer, and sat at the desk to continue thinking.

Since H. Kamerlingh-Onnes discovered that metal elements such as mercury and tin have superconductivity in 1911, there have been dozens of metal elements that show superconductivity under normal pressure.

There is currently no unified standard for the classification of superconducting materials.

Generally speaking, the most common classification is based on temperature.

Superconducting materials that need to be frozen with liquid helium to reach the critical Tc are called low-temperature superconductors; those frozen with liquid nitrogen are called high-temperature superconductors; and those that can achieve superconductivity at room temperature are called room-temperature superconductors.

At present, in addition to being able to use the BCS theory to explain low-temperature superconductivity, the scientific community has no complete and unified explanation for why high temperature and room temperature can also achieve superconductivity.

In materials science, it is normal to accidentally get the material first, and then analyze the material to find the mechanism.

In later life, when he studied copper-carbon-silver composite materials, he also tried to explore and explain the basic principles of high-temperature and room-temperature superconducting materials.

But in the end, he did not get an accurate answer, and he gave up the exploration of this aspect because he had no time to study controlled nuclear fusion and NS equations.

Of course, he did not study it in his previous life, but it does not mean that no one has studied the mechanism of high-temperature superconducting materials.

The mainstream view of later generations is that the superconducting pairing of copper oxide high-temperature superconductors does not originate from the traditional BCS electroacoustic coupling, but from the strong correlation effect between electrons.

When we studied physics in high school, we easily knew that each atom has a different number of electrons outside the nucleus.

For example, oxygen atoms have eight positively charged protons outside the nucleus, and carbon atoms have six electrons outside the nucleus.

Under normal circumstances, the electrons in the solid composed of these atoms are very stable, and each electron is considered independent and will not affect each other.

Just like the eight planets in the solar system, each planet has its own independent orbit and will not collide with each other.

However, in many substances, such as transition metal oxides, lanthanide oxides and other atoms, the outer electron orbits overlap greatly, and the electrons on the orbits are close to each other, and the increase in electrostatic energy cannot be ignored.

So these materials will produce a strong correlation effect.

And the strong correlation effect between electrons is the reason for many novel physical phenomena.

Such as the fractional quantum Hall effect in two-dimensional electron gas, the giant magnetoresistance effect in manganese oxide materials, the heavy fermion system, the metal-insulator phase transition in two-dimensional high-mobility materials, etc.

Therefore, in later generations, the mainstream explanation of the superconducting mechanism of high-temperature superconductivity and room-temperature superconductivity is the electron strong correlation effect.

But this explanation is only a theory and cannot be explained by models or mathematics.

And today, Xu Chuan felt that he might be able to give it a try.

Flipping through the experimental data of low-temperature copper-carbon-silver composite materials studied by Song Wenbo on the computer, Xu Chuan looked at it carefully, ready to start deducing the mechanism of high-temperature superconductivity after getting familiar with it.

At this moment, the mobile phone on the desk rang, and he picked up the phone. The call was from Gao Hongming.

"Academician Xu, the application from the Gucheng Supercomputing Center has been received. The time is five days later. Five days later, the Tianhe-1 supercomputer of the Gucheng Supercomputing Center will allocate the computing power you need to simulate and run the mathematical model in your hand."

Gao Hongming replied with the application on the phone.

Xu Chuan nodded and said, "I know, I will go there on time."

After hanging up the phone, he looked at the data on the computer and picked up the pen next to the manuscript paper.

"Five days, we should be able to find some directions, right?"

Xu Chuan whispered to himself, without thinking any more, and began to calculate on the manuscript paper with the pen in his hand.

"The low-energy physics of the layered structure shown in Figure 1 is mainly determined by the CuO2 plane. On the CuO2 plane, copper atoms form a square lattice, and there is an oxygen atom between the two nearest neighbor copper atoms. From the electronic structure, the electron orbits involved are mainly copper 3d orbits and oxygen 2p orbits"

"When a certain concentration of holes is doped into the parent material, it will enter the superconducting phase at low temperatures, which can be explained in mathematical language as:"

"H=μd, σ∑iσDi, σdiσ+μp, σ∑IσPI, σP, σ-∑.PI↑Pi↓."

"Considering the single-band Hubbard model of the copper 3dx2-y2 orbital, the hole doped on the oxygen 2p orbital will form a spin singlet bound state with the hole on the copper 3dx2-y2 orbital, which is the famous Zhang-Rice singlet."

"Establish a low-energy effective model for it as the t-J model, and calculate the Hamiltonian as:

Ht-j=-∑, σtijPg(Ci, σCj, σ+h.c.)Pg+J∑Si·Sj"

In the study, Xu Chuan looked at the data on the computer while verifying the strong electron correlation structure in the copper-carbon-silver composite material.

Using mathematics to calculate physics is a breakthrough in his deep study of mathematics in his life, and it is also one of his best research at present.

Immersed in it, he calculated the data while integrating the ideas in his mind.

This is a road to explain the mechanism of high-temperature superconductivity. Some people have walked it before, but only opened up a short distance. Now, he is moving forward.

Walking on this primitive road, the strong mathematical ability in this life is like a hatchet in his hand, cutting through thorns and brambles; and the research in physics in the previous life is more like a compass, guiding the direction and ensuring that he will not open up the wrong path.

The perfect combination of mathematics and physics, the last time it was advanced in the field of high-energy physics, particle information calculation, and this time, it is to go deep into the material discipline to explore the mystery between atoms and electrons.

Little by little, Xu Chuan only has the pen and paper on the desk in his eyes. At this moment, he seems to be walking in the dark, with a dark scene in front of him, and only a little lighthouse flashing in the distance guides him in the direction of progress.

Days passed by one by one, outside the window, the weather in late winter was abnormally heavy rain, and the sky was covered with dark clouds, covering the earth.

I don’t know how long it took, the rain finally stopped, and the sun was moving, trying to penetrate the dark clouds and sprinkle its brilliance on the world again.

In the study, I don’t know when I stopped writing, standing by the window and looking at the distance Xu Chuan, looking at the light that fell on the earth through the dark clouds after the rain.

Looking at the setting sun slowly falling in the sky, Xu Chuan's mouth curled up a smile.

When the Tyndall effect appears, light has a shape.

The rays of light that shine through the sky after the rain are leading the direction of civilization.

Although he did not find the superconducting mechanism of high-temperature superconductivity, he has found a feasible path.

The rest is to continue to go deeper along this path.

If the mechanism of high-temperature superconductivity can be completed, in the future, he may be able to obtain the superconducting state of high-temperature superconducting materials through mathematical calculations.

By that time, superconducting materials will no longer be an obstacle to the development of science and technology.

Even, maybe he can continue to deduce from this and find new and better room-temperature superconducting materials, and use them widely in all walks of life.

After all, the properties of the copper-carbon-silver composite materials he developed in later generations are somewhat biased towards ceramic materials. Although they can achieve superconductivity at room temperature and pressure, they are difficult to process and are easily disturbed.

This limited room-temperature superconducting material is OK for controlled nuclear fusion and particle colliders, but it is still difficult to use it widely in power generation, transmission, energy storage, weak current and other fields.

Especially for those equipment with relatively harsh working environments, it is even more difficult to use.

If a room-temperature superconductor similar to copper and iron metal materials can be found, then the existing scientific and technological development will usher in a real leap.

After thinking about it, Xu Chuan turned around and picked up the mobile phone from the desk, found Gao Hongming's number and dialed it.

In less than half an hour, Gao Hongming quickly rushed over from the controlled nuclear fusion industrial park.

"Academician Xu, you are looking for me."

Xu Chuan nodded, picked up the prepared hard drive and handed it over: "This contains a mathematical model for the plasma turbulence in the chamber of a controlled nuclear fusion reactor."

"Originally, I was going to go to Gucheng in person to verify the calculation, but now the situation has changed a bit, and I have some other things on my hands, so I am not going to go there in person. Please take this hard drive with you."

Hearing this, Gao Hongming quickly said: "It's not a big deal to go there, but if you don't go, I don't understand mathematical models and testing."

"If you really can't get away, I will give feedback to the higher-ups? Postpone a little time? It doesn't matter."

Xu Chuan thought for a while and said: "Postponement is not a solution. Let me call Academician Peng Hongxi and ask the two people in charge of the model optimization department to come out and accompany you."

"This model is optimized by them, and they are professionals in modeling and can go there instead of me."

"If there is really any problem at that time, you can also call me."

Gao Hongming thought for a moment and said, "That's fine, but if you don't go, I'm still a little unsure. After all, this is so important."

Xu Chuan smiled and said, "If everything goes well, I can't do much. Just bring me the data after the model verification."

Gao Hongming nodded and said, "Okay, in that case, I'll go find Academician Peng first."

Xu Chuan: "Thank you for your hard work, and have a safe trip."

Gao Hongming carefully put the hard drive in his hand into the anti-collision box he brought, and said, "I just did some miscellaneous work, Academician Xu, you are the one who is really working hard."

"Since you still have things to do here, I won't bother you any more."

"In addition, I will notify the people in the army and ask them to arrange people to escort the model to Gucheng with me."

"Don't worry, the model is there as long as the person is there!"