Chapter 341 152K high temperature superconductor!
After sending Gao Hongming away, Xu Chuan called Peng Hongxi again. After briefly explaining and arranging the test of the mathematical model, he plunged into the study again.
Although the copper-carbon-silver composite superconducting material developed by the Chuanhai Institute of Materials is a low-temperature superconductor, he found a glimmer of light leading to the mechanism of high-temperature superconductivity.
Compared with going to Gucheng to verify the mathematical model of ultra-high temperature and high pressure plasma turbulence, the significance of this theoretical work can be said to be more important.
At least in his own opinion, the importance is even higher.
It can be said that there are many people who can replace him in the verification of mathematical models of plasma turbulence, but it can be said that there are almost no people who can replace him in the work of searching for the superconducting mechanism of high-temperature superconducting materials.
Even if his mentor Witten came, he could not use mathematical language to explain the superconducting energy gap of superconducting materials.
This is no longer a problem that can be solved by pure mathematical ability.
No matter how strong your mathematical ability is, if you don't understand the basic characteristics of materials, if you don't understand the various properties of high-temperature superconducting materials, and if you don't understand the inherent characteristics and derived characteristics of materials, it will be impossible to make it.
In his previous life, he was unable to find the superconducting mechanism of high-temperature superconducting materials. On the one hand, he did not invest time in it.
At that time, he thought that it would be enough to get the superconducting material out. As for the mechanism, if he didn't study it, someone would study it, so it didn't matter.
On the other hand, his mathematical ability in his previous life was far inferior to that in this life.
In his previous life, he won the Fields Medal incidentally for solving the gap between Yang Mills' existence and quality.
His mathematical abilities are indeed among the best in terms of partial differential equations, nonlinear equations, calculation functions, etc., but mathematics is not just about these.
Algebra, number theory, geometry, calculus, topology, functional analysis, and probability theory. All in all, there are more than twenty major categories of mathematics.
And under each major category, there are numerous subcategories. For example, under algebra, there are linear algebra, group theory, field theory, Lie groups, Lie algebras, Kac-Moody algebra, ring theory, and more than a dozen different fields.
Not to mention his previous life, even in this life, he dare not say that he understands all fields in mathematics.
In the study, Xu Chuan continued to improve the superconducting mechanism of superconducting materials while sorting out the data about superconducting materials brought back from Chuanhai Laboratory.
Judging from current research, superconducting states are the product of electrons forming Ku-Bo pairs and then condensing. The core issue of the superconducting mechanism is the formation of electron-Kubonic pairs.
The superconductivity in cuprate superconductors is generally assumed by the CuO2 plane, and the nearby carrier library layer plays a role in adjusting the physical properties of the CuO2 plane.
However, due to the strong correlation characteristics of electrons, the physical properties of CuO2 cannot be described by the existing solid energy band theory.
So he needed to make a new mathematical description of solid energy generation theory.
In front of the desk, Xu Chuan stared at the data on the computer screen, his eyes bright, and murmured to himself:
"Figure 1a shows the structure of the BiO surface exposed after the dissociation of the Bi2212 single crystal sample. It can be seen that there is an incommensurate modulation structure along one direction."
"In high-temperature superconductors, the originally continuous closed Fermi surface calculated by the band theory does not appear. Due to the strong correlation effect, the Fermi surface becomes four Fermi arcs, with a high density of states at the end points of the Fermi arcs."
"So there are 7 scattering wave vectors between the 8 endpoints, which are described by q1...q7 respectively. After measuring the pattern formed by quasi-particle coherent scattering, Fourier transform can be used to obtain the values of these 7 wave vectors. Scattered bright spots.”
"This can be screened using phase-sensitive quasi-particle coherent scattering (Phase-Referenced Quasi-Particle Interference, PR-QPI for short) technology. This can outline the information of the Fermi surface in q-space."
"However, in fact, this physical quantity is a complex variable at any q point and has a phase, that is, r(q, E)=|r0(q, E)|exp[ij(q, E)]"
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In front of the computer, Xu Chuan analyzed the data of copper-carbon-silver composite materials in his mind, and refined his theories and ideas in his mind.
Unlike mathematical arguments, the exploration of materials physics does not require long mathematical calculations.
Mathematics only plays a key foundational role in this process. More importantly, it is how to explain related phenomena through a complete set of theories.
This is actually somewhat similar to theoretical physics. Just like when Einstein first proposed the theory of relativity, he first gave the initial form of general relativity and then improved it bit by bit.
In the process of improving the theory of relativity, mathematical tools are used to confirm it bit by bit through the gravitational field equations, Mach principle, space-time diagrams, etc.
This is probably the commonality of all natural subjects. In the end, the research must be attributed to the commonality of mathematics.
If a theory cannot be logically consistent or verified mathematically, then no matter how perfect the theory is, it may only be a flash in the pan.
"Perhaps, I have found a suitable path!"
Looking at the images and data on the computer, Xu Chuan's eyes became deeper and deeper, like a vast ocean, containing countless knowledge.
Quickly taking out a new stack of manuscript paper from the drawer, he picked up the pen and began to deduce.
"rr(q,-E)=|r(q,-E)|cos[j(q,E)-j(q,-E)]"
"Based on the physical quantities of the phase reference calculated from the experimental data, each small dotted circle marks the position and intensity integration area of 7 scattering spots. It can be seen that in the case of d-wave energy gap, q1, q4, q5 correspond to Energy gaps have the same sign"
"The QPI intensity of the phase reference can be obtained rr(q,-E)=|r(q,-E)|cos[j(q,E)-j(q,-E)]. And (d), (e ) and (f) show the integral of rr(q,-E) intensity within the small circle of the dotted line, q2, q3, q6, q7 correspond to the energy gap inverse sign scattering."
“In this model, if we only consider the square lattice formed by copper lattice points, i and j are indicators of copper lattice points, in theory ci and σ are usually regarded as electron annihilation operators in a general sense, Then."
The black pen wrote down one by one on the white A4 paper.
Xu Chuan's eyes became calmer as he calculated the energy gap data and phase physics quantities of copper-carbon-silver superconducting materials.
Finally, he stopped writing and looked at the last line of calculations on the manuscript paper.
【S→=C〃σc】
"It turns out that the energy gap in superconductors is d-wave symmetrical, at least in copper-carbon-silver composite superconducting materials."
"The energy gap can be obtained using single-band Hubbard mathematics and the Gutzwiller projection operator. Although this method is not used in all cases, the low-energy effective theory in the case of strong coupling is basically the same."
"If you use the theory of the t-J model and other similar models and the renormalized mean field method to deal with high-temperature superconducting materials, you can first use the Gutzwiller approximate renormalization factor, and the second step is to use the standard mean field method for further analysis. Process.”
"In this way, the superconducting energy gap of high-temperature superconducting materials can be calculated step by step through experimental data."
"And this approach promises to be a powerful means of determining sign reversal of the energy gap function in other unconventional superconductors."
"Perhaps in the near future, high-temperature superconductivity will usher in a vigorous development."
Looking at the theories and calculations on the manuscript paper, Xu Chuan let out a long breath.
After freeing up time to go to Gucheng to check the mathematical model of plasma turbulence, he had initially figured out the superconducting mechanism characteristics of high-temperature superconducting materials.
All that's left is to find more data on high-temperature superconducting materials to verify this theory. After getting up and stretching his muscles, Xu Chuan sat back at the desk again.
After sorting out the manuscript paper, he began to transfer the things on the manuscript paper to the computer bit by bit to write the paper.
Of course, it is currently impossible for this paper to be made public.
Although the study of the superconducting mechanism properties of high-temperature superconducting materials is one of the hottest fields in the field of superconducting materials today, if his paper is thrown out, it may explode the pond in an instant, making him a top expert in the field of superconducting materials. ox.
But correspondingly, this will also point out a way for others to study high-temperature superconducting materials.
Therefore, this paper can only be kept in my hands for now.
But Xu Chuan didn't pay much attention.
After he makes the high-temperature superconducting material, it won't be too late to announce it.
After sorting out the papers on the manuscript paper and inputting them into the computer, Xu Chuan got up and went straight to the Chuanhai Materials Laboratory.
He has initially understood the superconducting mechanism characteristics of high-temperature superconducting materials. If he wants to use it, it is best to establish a strongly correlated tj model for calculation.
However, it takes at least half a month to build a model and then test it, even the most basic version.
He can't wait now. He wants to go to the laboratory to test it and see if he can further optimize the superconducting material based on the data and theory he calculated.
After arriving at the Sichuan-Hai Materials Research Institute in a hurry, Xu Chuan found Fan Pengyue and asked him to arrange a laboratory for himself.
The institute originally did not have any extra laboratories. After all, the expansion had only been completed for less than two months, and the personnel recruited and the equipment purchased were not very complete.
Coupled with his previous request for a large amount of research on superconducting materials and carbon-based materials, it is now at full capacity.
However, Song Wenbo, who had previously studied copper-carbon-silver composite materials, was assigned to analyze the materials, and the laboratory he originally used was temporarily vacant and could be used.
In the laboratory, Xu Chuan personally controlled the vacuum metallurgical equipment to produce copper-carbon-silver composite materials.
Compared with other nano-manufacturing methods such as physical grinding, mechanical ball milling, and vapor deposition, vacuum evaporation, heating, high-frequency induction and other methods are used to vaporize the raw materials or form equal particles, and then quench them to obtain high-purity nanomaterials. , raw materials with good crystal structure and controllable particle size.
Materials with perfect crystallization and consistent particle size are very important in the manufacturing of materials, especially when studying materials in the laboratory.
Of course, there are also disadvantages. This method of preparing nanomaterials requires high equipment and preparation technology.
However, things that can be solved with money are nothing to Xu Chuan.
On the side, Fan Pengyue and Song Wenbai were fighting in the laboratory.
Of course, they are also a little curious about what this person is going to study, or how he is going to prepare copper-carbon-silver composite nanomaterials.
Xu Chuan had previously obtained the data on Song Wenbo's ultra-low-temperature copper-carbon-silver composite superconducting material, and obviously went to study it.
In just ten days, can you find some discoveries or inspirations from it?
Neither of them dared to think about deeper things.
They all just thought that Xu Chuan had found some clues about possible optimized copper-carbon-silver composite materials by studying the data of ultra-low-temperature copper-carbon-silver composite superconducting materials.
Honestly, that's amazing.
After all, the time is so short, and the material data is not so easy to analyze.
As for using these data to find the superconducting mechanism behind high-temperature superconducting materials, neither of them had even thought about it.
If the superconducting mechanism of high-temperature superconducting materials was so easy to study, it would not be the case that iron-based, copper-based, graphene and other high-temperature superconducting materials have been released now, and the mechanism has not yet been found.
In the laboratory, Xu Chuan, wearing a white coat, protective mask and goggles, was concentrating and carefully controlling the RF magnetron sputtering equipment to sputter the prepared nanomaterials on the SrTiO3 substrate.
This step takes about two minutes to allow the nanomaterials to completely cover the SrTiO3 substrate and form a thin film on it.
Then 2% (volume fraction) of multi-walled carbon nanotubes (CNTs) and carbon nanotubes modified by surface Cu plating were added as reinforcing phases.
After a series of treatments, it is finally heat treated under inert gas protection at a temperature of 860°C-900°C for 30-50 minutes to form a copper-carbon-silver composite film on the SrTiO3 base layer.
And this film is what Xu Chuan needs!
After staying in the laboratory for two full days, it was not until late at night and early the next morning that Xu Chuan's tense nerves relaxed.
In the vessel in his hand, a silver-gray film no bigger than a child's palm was lying there quietly. This is the result of his two busy days.
With a long sigh of relief, Xu Chuan handed the transparent vessel in his hand to Song Wenbai and said, "Professor Song, please test the superconducting mechanism of this piece of material."
"If my calculations are correct, it should reach the critical Tc around 152K."
After concentrating on it for a day, he now really has no energy to do the test and can only hand it over to others.
Hearing this, Song Wenbai opened his mouth but hesitated, and finally nodded and took the material.
Testing superconducting materials is not difficult and can be done with equipment such as cryostats and Dewar liquid nitrogen vessels.
It's just that he doesn't quite believe this person's critical Tc of 152K.
What is the concept of critical Tc of 152K?
Converted to degrees Celsius, it is almost -121.15°C. This temperature sounds very low, but in the current superconducting material world, it is very high.
Putting aside those superconducting materials that require high-pressure conditions, the current copper-based high-temperature superconductor can reach a superconducting temperature of 94.9K, and the pressure can reach 125K, which is about -178.2°C and -148.15°C when converted into degrees Celsius.
There is a temperature difference of 30°C. Don’t underestimate this. You must know that the Tc critical temperature of 94.9K for copper-based high-temperature superconducting materials has not been broken for almost ten years.
As for iron-based superconductors, although the limit can reach -23°C superconductivity, only a few can be manufactured in the laboratory at great cost.
Not to mention the small amount, it is also extremely easy to contaminate. Casual exposure to the air will cause superconducting failure, so it does not have much comparative value.
And if the film in his hand can really achieve superconductivity at a temperature of 152K, then the high-temperature superconducting industry will usher in earth-shaking changes.
More importantly, his boss had calculated this number in advance.
He no longer dared to think about the meaning of this.
(End of chapter)