Chapter 341: Mechanism and strong correlation effect of high-temperature superconductivity
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, so they could only wait quietly.
After clearing the thoughts in his mind, Xu Chuan raised his head, looked at Song Wenbai with shining eyes, and said:
"Professor Song, during the next period of time, you and your team will temporarily stop the research on copper-carbon-silver composite materials, and instead focus on analyzing the ultra-low-temperature superconducting copper-carbon-silver composite materials that you have previously developed."
"I need more information and analysis data on this material!"
Hearing this, Song Wenbo was stunned for a moment, then quickly nodded and replied: "It's no problem to turn away from research and turn to analysis. It's just about analyzing materials. The equipment of our research institute may still be somewhat lacking."
"For example, there are no fragmentation chromatographs or inductively coupled plasma emission spectrometers for structural analysis. Without these equipment, the analyzed data is not perfect."
Xu Chuan: "That's no problem. Fan will always communicate with you about the relevant equipment. Buy what you should buy. Equipment is not meant to be used only once."
Fan Pengyue nodded and said: "The research institute has just expanded, and there is indeed some equipment that has not yet been purchased. However, this has been arranged in the procurement plan. It is just that the priority was lower before. Now that it is needed, it can be used in advance.
Procured.”
Xu Chuan: "If it takes a long time to buy new ones, you can try buying second-hand ones from other domestic laboratories. It doesn't matter if the price is higher. I need to get the data as soon as possible."
In the conference room, Xu Chuan asked some questions about the experimental data of ultra-low-temperature superconducting copper-carbon-silver composite materials, and then left Sichuan-Hai Materials Research Institute with part of the data.
Back at the villa, he inserted the USB flash drive in his hand into the computer, took out a stack of manuscript paper from the drawer, sat at the desk and continued to meditate.
Since H. Kamerlin-Onnes discovered that mercury, tin and other metal elements have superconductivity in 1911, there have been dozens of metal elements that exhibit 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 critical tc are called low-temperature superconductors; those that are frozen with liquid nitrogen are called high-temperature superconductors; and those that can reach superconductivity at room temperature are called room-temperature superconductors.
.
At present, in addition to using BC theory to explain low-temperature superconductivity, there is no complete and unified explanation for why superconductivity can be achieved at high temperatures and room temperatures.
In materials science, it is normal to first create materials accidentally and then analyze the materials to find the mechanism.
Later, when he developed 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, we did not get an accurate answer. In addition, we did not have time to study controllable nuclear fusion and the n equation, so we gave up exploring this aspect.
Of course, he didn't study it in his previous life, but that doesn't mean no one studies the mechanism of high-temperature superconducting materials.
The mainstream view in later generations is that the superconducting pairing of cuprate high-temperature superconductors does not originate from the traditional bc electroacoustic coupling, but from the strong correlation effect between electrons.
When we studied physics in high school, we easily learned that there are different numbers of electrons outside the nucleus of every atom.
For example, an oxygen atom has eight positively charged protons outside its nucleus, and a carbon atom has six electrons outside its nucleus.
Under normal circumstances, the electrons in the solid composed of these atoms are very stable, and each electron is regarded as independent and does 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 peripheral electron orbits overlap greatly, the electrons in the orbits are close to each other, and the increase in electrostatic energy cannot be ignored.
As a result, these materials will produce strong correlation effects.
The strong correlation effect between electrons is the cause of many novel physical phenomena.
Such as the fractional quantum Hall effect in two-dimensional electron gas, the giant magnetoresistance effect in manganese oxide materials, heavy fermion systems, metal-insulator phase transition in two-dimensional high-mobility materials, etc.
Therefore, in later generations, the mainstream explanation of the superconducting mechanisms of high-temperature superconductivity and room-temperature superconductivity was based on the strong electron correlation effect.
It's just that this explanation is just a theory and cannot be explained through models or mathematics.
Today, Xu Chuan thought he might give it a try.
Looking through the experimental data on the low-temperature copper-carbon-silver composite material studied by Song Wenbo on the computer, Xu Chuan looked at it carefully, preparing to start deducing the mechanism of high-temperature superconductivity after getting familiar with it.
At this moment, the cell phone on the desk rang. He picked it up and the call was from Gao Hongming.
"Academician Xu, the application from the Gucheng Supercomputing Center has been received. In five days, the Tianhe-1 supercomputer at the Gucheng Supercomputing Center will allocate the computing power you need to simulate the operation in your hands.
mathematical model.”
On the phone, Gao Hongming responded with an application.
Xu Chuan nodded and said, "I understand, I will be there on time."
After hanging up the phone, he looked at the data on the computer and picked up the pen beside the manuscript paper.
"In five days, we should be able to find some directions, right?"
Xu Chuan whispered to himself, without thinking any more, he started calculating 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 cuo plane. On the cuo plane, copper atoms form a square lattice, and there is an oxygen atom between the two nearest neighbor copper atoms. From the electron
From a structural point of view, the electron orbits involved are mainly the 3d orbital of copper and the p orbital of oxygen."
"When the parent material is doped with a certain concentration of holes, 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 3d-y orbital, the hole incorporated in the oxygen p orbital will form a spin singlet bound state with the hole in the copper 3d-y orbital, that is, the famous zhang-rice single state.
state."
"Establishing a low-energy effective model for it is the t-j model, and calculating the Hamiltonian is:
ht-j=-∑,σtijpgci,σcj,σ .pg j∑i·j”
In the study, Xu Chuan was looking at the data on the computer while checking the strong electronic correlation structure in the copper-carbon-silver composite material.
Using mathematics to calculate physics is a breakthrough in his lifelong study of mathematics, and it is also one of his current best researches.
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. Someone has walked it before, but it has only opened up a short journey. Now, he is moving forward.
Walking on this primitive road, the powerful mathematical ability in this life is the hatchet in his hand, cutting through obstacles; while the research in physics in the previous life is more like a compass, guiding the direction, ensuring that he will not open up the wrong path.
the way.
The perfect combination of mathematics and physics. The last time we promoted particle information calculation in the field of high-energy physics, this time we went deep into the material science to explore the mysteries between atoms and electrons.
Little by little, Xu Chuan could only see the pen and paper on the desk. At this moment, he seemed to be walking in the dark. His eyes were completely dark, with only a lighthouse shining in the distance guiding his direction.
As the days passed, outside the window, the weather in the late winter season was abnormally raining heavily, and the sky was covered with dark clouds, covering the earth.
I don’t know how long it took, but the rain finally stopped, and the sun was moving, trying to shine its light through the dark clouds to the world again.
In the study room, I don't know when I stopped writing. I stood by the window and looked at Xuchuan in the distance. I was fascinated by the light falling on the earth through the dark clouds after the rain.
Looking at the sunset slowly setting in the sky, a smile appeared on Xu Chuan's lips.
When the Tyndall effect occurs, light takes on a shape.
The streaks of light that shine through the sky after rain and clear skies are leading the way forward for civilization.
Although he has not found the superconducting mechanism of high-temperature superconductivity, he has found a feasible way.
All that's left is to continue 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 this, find new and better room-temperature superconducting materials, and use them widely in various industries.
After all, the properties of the copper-carbon-silver composite materials he later developed were somewhat biased toward ceramic materials. Although they could achieve superconductivity at normal temperatures and pressures, they were difficult to process and shape, and were susceptible to interference.
This kind of limited room-temperature superconducting material can be used in top scientific research equipment such as controlled nuclear fusion and particle collider, but it is still very difficult to widely use it in fields such as power generation, power transmission, energy storage, and weak electricity.
difficult.
Especially those equipment with relatively harsh working environment cannot be used.
If a room-temperature superconductor similar to copper-iron metal materials can be found, then the development of existing science and technology will usher in a real leap.
After thinking about it, Xu Chuan turned back and picked up his cell phone from the desk, found Gao Hongming's number and dialed it.
In less than half an hour, Gao Hongming rushed over from the Controlled Nuclear Fusion Industrial Park.
"Academician Xu, please look 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 controllable nuclear fusion reactor chamber."
"Originally, I was planning to go to Gucheng in person to check the calculations, but now the situation has changed, and I have some other matters in hand, so I am not planning 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, can I give you feedback here? Extend it for a little longer? It doesn't matter."
Xu Chuan thought for a while and said: "Delay is not the solution. Let me call Academician Peng Hongxi and ask the two people in charge of the modeling department to come out and accompany you."
"This model was optimized by them, and they are professionals in modeling. They can replace me."
"If you really have any problems then, you can also call me."
Gao Hongming thought for a moment and said: "It's okay, but if you don't go, I still feel a little unsure. After all, this matter is so important."
Xu Chuan smiled and said: "If everything goes well, I won't be able to do much, just bring back the data after model verification."
Gao Hongming nodded and said, "Okay, in that case, I'll go find Academician Peng later."
Xu Chuan: "Thank you for your hard work. Have a nice trip."
Gao Hongming carefully put the hard drive in his hand into the anti-collision box he brought, and said: "I just did some odd jobs, Academician Xu, you are the real hard worker."
"Since you have something else 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 manpower to escort this model to Gucheng safely with me."
“Don’t worry, the people are here and the models are here!”