Great Country Academician

After sending Gao Hongming away, Xu Chuan called Peng Hongxi again, and 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 produced by the Chuanhai Materials Research Institute is a low-temperature superconductor, he found a glimmer of light leading to the high-temperature superconducting mechanism from it.

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 the mathematical model of plasma turbulence, but it can be said that there are almost no people who can replace him in the work of finding 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 the 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 don't understand the data of various aspects such as the inherent characteristics and derived characteristics of materials, it is 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 devote time to it.

At that time, he felt that it would be enough to get out the superconducting material. As for the mechanism, if he doesn't study it, someone will study it. That's not important.

On the other hand, his math ability in his previous life was far worse than in this life.

In his previous life, he won the Fields Medal because he solved the Yang-Mills gap between existence and quality.

His mathematical ability in partial differential equations, nonlinear equations, calculation functions, etc. is indeed among the top batch, but mathematics is not only these.

Algebra, number theory, geometry, fractions, topology, functional analysis, and probability theory are all summed up. There are more than 20 major categories of mathematics.

For each major category, there are many subcategories below, such as linear algebra, group theory, field theory, Lie groups, Lie algebras, Kac-Moody algebras, ring theory, etc. under a dozen different fields.

Not to mention the last life, even in this life, he dare not say that he knows all the 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 the current research, the superconducting state is the product of electrons forming Cooper pairs and then condensing. The core issue of the superconducting mechanism is the cause of the electron Cooper pairs.

The superconductivity in cuprate superconductors is generally undertaken 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 of electrons, the physical properties of CuO2 cannot be described by the existing solid energy band theory.

So he needs to make a new mathematical description of solid energy generation.

In front of the desk, Xu Chuan stared at the data on the computer screen, his eyes were bright, and he muttered to himself:

"Figure 1a shows the structure of the exposed BiO surface 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 and closed Fermi surface calculated by the energy band theory does not appear. Due to the strong correlation effect, the Fermi surface becomes four segments of Fermi arcs, and there is a high density of states at the ends 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 the coherent scattering of quasi-particles, using Fourier transform, the 7 wave vectors can be obtained Scattering bright spots."

"This point can be discriminated by phase-sensitive quasi-particle coherent scattering (Phase-Referenced Quasi-Particle Interference, PR-QPI for short) technology. In this way, the Fermi surface information can be outlined in q-space."

"However, in fact, this physical quantity is a complex variable at any point q, and has a phase at the same time, that is, r(q, E)=|r0(q, E)|exp[ij(q, E)]"

In front of the computer, Xu Chuan analyzed the data of the copper-carbon-silver composite material in his mind, and perfected theories and ideas in his mind.

Unlike mathematical arguments, the exploration of material physics does not require long mathematical calculations.

Mathematics only plays a key foundational role in this process, and more importantly, how to explain related phenomena through a complete set of theories.

This is actually somewhat similar to theoretical physics. Just like Einstein first proposed the theory of relativity, he first gave the initial form of general relativity, and then improved it a little bit.

In the process of perfecting the theory of relativity, through the gravitational field equation, Mach's principle, space-time diagram, etc., use mathematical tools to confirm it bit by bit.

This is probably all natural subjects, and the research must be attributed to the commonality of mathematics in the end.

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 seawater of 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)]"

"According to the physical quantity of the phase reference calculated from the experimental data, each small dotted circle marks the position and intensity integration area of ​​the 7 scattering spots. It can be seen that in the case of the d-wave energy gap, q1, q4, and q5 correspond to The same sign as the energy gap"

"The available phase referenced QPI strength rr(q, -E) = |r(q, -E)| cos[j(q, E) - j(q, -E)]. And (d), (e ) and (f) show the integral of the intensity of rr(q, -E) in the small dotted circle, and q2, q3, q6, q7 correspond to the energy gap backscattering.”

"In this model, if only the square lattice formed by copper lattice points is considered, i, j are indicators of copper lattice points. In theory, ci, σ are generally regarded as electron annihilation operators in a general sense, but."

The black signature pen writes one by one on the white A4 paper.

With the calculation of the energy gap data and phase physical quantities of the copper-carbon-silver superconducting material, Xu Chuan's eyes became more and more calm.

Finally, he stopped the pen in his hand and looked at the last line of calculation on the manuscript paper.

【S→=C〃σc】

"It turns out that the energy gap in superconductors is d-wave symmetric, 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 t-J model and other similar models and the renormalized mean-field method to deal with high-temperature superconducting materials, you can first use Gutzwiller to approximate the renormalization factor, and the second step is to use the standard mean-field method for further deal with."

"In this way, the superconducting energy gap of high-temperature superconducting materials can be calculated step by step based on experimental data."

"And this method promises to be a powerful means to determine the sign inversion 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 calculation formulas on the manuscript paper, Xu Chuan let out a long breath.

Taking the time to go to Gucheng to check and calculate the mathematical model of plasma turbulence, he has initially grasped the superconducting mechanism characteristics of high-temperature superconducting materials.

All that remains 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 tidying up the manuscript paper, he began to transfer the things on the manuscript paper to the computer to write a thesis bit by bit.

Of course, it is currently impossible for this paper to be made public.

Although the research on the superconducting mechanism of high-temperature superconducting materials is one of the hottest fields in the field of superconducting materials, throwing out his paper may instantly detonate this pond, making him a top researcher in the field of superconducting materials. ox.

But correspondingly, this will also point out a way for others to study high-temperature superconducting materials.

So this paper can only be hidden in the hands for now.

But Xu Chuan didn't care too much.

After he has made the high-temperature superconducting material, it will not 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 already figured out the superconducting mechanism 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 for the most basic version.

He can't wait any longer now, he wants to go to the laboratory to experiment, and see if he can make a further optimization on the superconducting material based on the data and theory he calculated.

All the way to Chuanhai Materials Research Institute at lightning speed, Xu Chuan found Fan Pengyue and asked him to arrange a laboratory for himself.

The institute didn't have any redundant laboratories. After all, it was only expanded for less than two months, so the recruited personnel and purchased equipment 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 fully loaded.

However, Song Wenbai, who previously studied copper-carbon-silver composite materials, was assigned to analyze the materials, and the laboratory he used to use was temporarily vacant, which could be used for a while.

In the laboratory, Xu Chuan personally manipulated vacuum metallurgy equipment to manufacture copper-carbon-silver composite materials.

Compared with other nano-manufacturing methods such as physical pulverization, mechanical ball milling, and vapor deposition, vacuum evaporation, heating, high-frequency induction, etc. are used to gasify raw materials or form equal particle bodies, and then quench to obtain high-purity , Raw materials with good crystal structure and controllable particle size.

A material with perfect crystallization and uniform particle size is very important in the manufacture of materials, especially in the research of materials in the laboratory.

Of course, there are also disadvantages. The preparation of nanomaterials by this method requires high equipment and preparation technology.

But 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 to prepare copper-carbon-silver composite nanomaterials.

Before Xu Chuan got the data of Song Wenbai's ultra-low temperature copper-carbon-silver composite superconducting material, he obviously went to study it.

Can you find some discoveries or inspirations in just ten days?

Neither of them dared to think about deeper things.

They all 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 already amazing.

After all, with such a short time, the data on materials is not so easy to analyze.

As for using these data to find the superconducting mechanism behind high-temperature superconducting materials, neither of them even thought about it.

If the superconducting mechanism of high-temperature superconducting materials is so well studied, it is unlikely that iron-based, copper-based, graphene and other high-temperature superconducting materials have come out now, and the mechanism has not been found yet.

In the laboratory, wearing a white coat, a protective mask and goggles, Xu Chuan carefully manipulated the RF magnetron sputtering equipment and sputtered 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 add 2% (volume fraction) of multi-walled carbon nanotubes (CNTs) and surface Cu-modified CNTs as a reinforcing phase.

After a series of treatments, it is finally protected by inert gas and heat-treated at a temperature of 860°C-900°C for 30-50 minutes to form a layer of 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, Xu Chuan's tense nerves did not relax until late at night the next morning.

In the vessel in his hand, a silver-gray film no bigger than a child's palm was lying quietly there. This is the result of his busy two days.

After 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 material."

"If my calculations are correct, it should reach a critical Tc around 152K."

After concentrating on it all day, he really doesn't have the energy to do the test now, so he can only hand it over to others.

Hearing this, Song Wenbai opened his mouth to speak but stopped, finally nodded and took the materials.

It is not difficult to test superconducting materials, and it can be carried out with equipment such as cryostats and Dewar liquid nitrogen containers.

It's just that he doesn't quite believe the critical Tc of 152K.

What is the concept of the critical Tc of 152K?

Converted into degrees Celsius, it is almost -121.15°C. This temperature sounds very low, but it is very high in the current superconducting material field.

Aside from 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 almost -178.2°C and -148.15°C when converted into degrees Celsius.

The temperature difference is 30°C. Don’t underestimate this point. 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 superconductivity, although the limit can reach -23°C superconductivity, it can only be manufactured in a very small number of laboratories at a great cost.

Not to mention the small amount, it is also extremely easy to pollute, and casual exposure to the air will cause superconducting failure, so there is not much comparative value.

And if the thin film in his hand can really achieve superconductivity at a temperature of 152K, then the high-temperature superconductivity industry may usher in earth-shaking changes.

More importantly, he, the boss, had calculated this number in advance.

He no longer dared to think about the meaning of this.