Time passed quickly, and in the following time, Xiao Yi began to join the design of Science Island Laboratory.
For example, site selection, and how to design the overall structure of the laboratory based on the site selection, etc.
To this end, Xiao Yi also spent a few days studying laboratory design, as well as architectural design and other related books.
After all, this laboratory was specially built for him, and he, the future director of Science Island Laboratory, had to think about where he would probably work for a long time in the future.
After a few days of simple research, he could almost confidently say that even if he was not a master architect, he could still be called a top design expert.
Architectural design is basically how to play tricks on structural mechanics, which also needs to take into account the relevant properties of various building materials.
Considering that a building is often relatively large, it also makes the entire design appear more complex.
It's just that, for Xiao Yi, if it's just complicated, it's not a problem at all.
It's nothing more than calculations, and calculations are the least of his problems.
Asking him to participate in Super Brain or something like that is basically a dimension reduction attack.
He had actually received a program invitation from Super Brain before, but of course he was not interested in this kind of program.
All in all, after returning from his studies, the suggestions he made from time to time surprised the design team responsible for designing Science Island Laboratory.
Their team has taken over many laboratory-related designs, such as a bunch of research institute laboratories on Science Island, etc., with their participation. In addition, they have also taken on the design tasks of many national key laboratories and even national laboratories. Even foreign laboratories, they have participated in the design, and they can be regarded as a relatively top team in the world.
But almost every suggestion put forward by Xiao Yi can bring them some inspiration, or is better than their original design, which makes them wonder, is it possible for someone with a high IQ to be proficient in this kind of architectural design?
Fortunately, Xiao Yi is not a full-time designer, otherwise how could they still make a living?
In this way, with the help of Xiao Yi, their design speed has also been accelerated.
In addition to laboratory design, another important point is to purchase various experimental equipment, instruments and other supplies.
These things are the key to a laboratory. After all, laboratories are used for experiments. Only sufficiently advanced experimental equipment can help a laboratory continue to make more excellent conclusions.
Therefore, Xiao Yi has also contacted the world's top experimental instruments and equipment manufacturers and started to contact and order related experimental instruments and equipment.
Xiao Yi had already thought about which experimental instruments to order, mainly for the effect of Material Mastery.
For example, for some experimental instruments with the same price, some experimental instruments have many additional functions, but their resolution and clarity are slightly weak, while some experimental instruments do not have many additional functions, but their resolution and clarity are high enough.
For Xiao Yi, what he needs is the latter with high resolution and clarity.
No matter how awesome the extra functions of the experimental instrument are, can they still compare to the extra functions that come with its plug-in?
joke!
Do you know what a plug-in is?
Of course, considering that he currently has enough funds, both of them can still be satisfied together.
Anyway, of the 500 million, a full 400 million can be used to purchase experimental instruments, and the remaining 100 million is for the cost of building materials. After all, the building materials needed to build a laboratory must be relatively high-end, such as maintaining internal temperature. For experiments, the impact of temperature is often very large.
Coupled with the high requirements of Xiao Yi, the cost of 100 million is considered relatively reasonable.
As for the land price, that doesn't exist. Science Island Laboratory has more than 10 acres of land in total, which was completely donated by the Fei City government. According to the land price on Science Island, it is almost equivalent to three to four billion.
This is considered the Fei City government's investment in this laboratory, but it is not included in provincial-level funding.
In this way, the construction of Science Island Laboratory is on track. The construction time is about one year, of which the design and design acceptance are expected to take three months. The remaining nine months are the actual construction and subsequent decoration.
As for Xiao Yi, apart from paying attention from time to time, he was not idle the rest of the time.
Cracking the mechanism of high-temperature superconductivity has reached a very critical point!
"Local electron density fluctuations enhance the interaction between electrons..."
"Local electron density fluctuations... local electron density fluctuations..."
Xiao Yi was thinking about this matter deeply in his mind.
"How is the electron interaction enhanced?"
In his mind, he began to review the discovery process of BCS theory in the history of physics, especially the discovery process of Cooper pair.
Cooper pair is an electronically correlated phenomenon, but it is not a strongly electronically correlated system.
However, in complex material systems such as high-temperature superconductors, strong electron correlation and the concept of Cooper pair may work together. Therefore, reviewing this process may also help him reveal the mechanism of high-temperature superconductivity.
BCS theory, explains the superconducting mechanism of certain low-temperature superconducting metals.
In the 1950s, physicists such as John Bardeen had proposed that lattice vibrations might produce an attraction between electrons, which was different from the usual Coulomb repulsion between electrons.
Then, Leon Cooper, who proposed Cooper pair, began to study the behavior of electrons near the sea surface of Fermi. Fermi Surface refers to the maximum energy boundary of electrons at absolute zero.
"In Cooper's study, he was assuming that if two electrons have zero total momentum, which is the same magnitude but in opposite directions, and they interact by exchanging phonons, then this interaction can lead to the formation of an electron pair."
Xiao Yi simulated Cooper's original derivation process on the scratch paper.
"... The most important thing is that he proved through Quantum Mechanics calculations that when the temperature is lower than a certain critical value, the formation of electron pairs is spontaneous. This spontaneously formed electron pair can reduce the total energy of the system, making the entire system more stable at low temperatures. Even a weak electron-phonon interaction can lead to the formation of Cooper pair."
"Well... here's the key, because the temperature is low enough, there is an energy gap between the electronic states near Fermi Surface, so a single electron cannot be easily excited to a higher energy state, and the temperature has not reached the threshold that exceeds the pairing energy between Cooper pair, so the interaction between electrons and phonons can make Cooper pair shape."
"But at high temperatures, electrons are excited to higher states, and thermal noise will cause random scattering between electrons. Therefore, these traditional superconductors explained by BCS theory cannot achieve superconductivity at high temperatures."
"For lanthanum barium copper oxides such as Yttrium Barium Copper Oxide, as well as some iron-based superconductors, they exhibit strongly correlated electronic systems at higher temperatures, thereby achieving superconductivity."
"For example, in Copper Oxide High-Temperature Superconductor, Cooper pair is usually considered to have d-wave symmetry rather than s-wave symmetry in traditional superconductors..."
"Local electron density fluctuations... local electron density fluctuations..."
Xiao Yi took out a pen and listed various related information on the scratch paper.
Looking at all this information, his mind also recalled the previous inspirations, until finally, a burst of light suddenly burst out in his eyes.
"Spin density wave! No, it should be local spin density wave!"
"If local spin density waves are also substituted..."
"Coupled with local electron density waves..."
"If we combine these two theories to describe the strongly correlated electronic system..."
It works!
No matter what, this can definitely be regarded as a research angle.
Without any nonsense, he took out a new piece of scratch paper.
"Well... it's not possible to directly interpolate between the two. It would be best to start from other directions."
"That's right! Hubbard model!"
His eyes lit up, and the pen in his hand continued to move.
[The Hamiltonian is expressed as: H=t∑[i, j], σ(ciσcjσ+h. c.)+U∑ini↑ni↓]
[Where, t is the amplitude of the electronic transition, and U is the energy of electron interaction at the same grid point.]
"Then there are spin density waves... which can be described by a periodic arrangement of spins."
[[Szi]=S0cos(QRi)]
"Well... let's simulate the behavior of electrons in iron-based superconductors first."
"But we have to build a model first."
After almost two hours passed like this, Xiao Yi completed the modeling and input the model into the computer.
"The next step is to connect to the server."
Xiao Yi spent several hundred W to buy the server, but it is still in USTC.
So, I quickly connected to the server, put the model up and started running.
The method used in the model is Absolute Electronic Computation. The model he created is now Materials Science, and is also a model widely used in condensed matter and other fields.
For analyzing his model, there is basically no better or more suitable model.
However, in addition to Absolute Electronic Computation, he also used another method called density matrix renormalization group DMRG. DMRG is particularly suitable for processing low-dimensional strongly correlated electronic systems, especially in one-dimensional and quasi-one-dimensional systems.
Although FeSe/SrTiO3 is a two-dimensional material, in some cases, it can be simplified to a quasi-one-dimensional chain to study local phenomena, thus helping Xiao Yi to deeply study the local electronic state distribution and spin density wave behavior caused by iron vacancies.
Soon, the results came out.
"Sure enough, the local electron density fluctuations caused by iron vacancies and the spin density waves produced an effective attractive interaction near Fermi Surface... Looking at this numerical result, this interaction is similar to the phonon-mediated attraction in the traditional Cooper pair formation mechanism, but its source is the local magnetic fluctuations caused by the spin density waves."
"Magnetic fluctuations..."
His eyes became brighter and brighter.
"Local electron density fluctuations lead to rearrangements of electronic states, making it easier for certain electronic states to form pairs in these regions. Spin density waves cause magnetic fluctuations in these local regions. These fluctuations enhance the attractive interactions between electrons... and so on!"
His expression suddenly became serious, and he observed the simulated data again.
Until finally, he re-listed the two models on the scratch paper next to him.
One of them is a local electron density wave model, and the other is a local spin density wave model.
After observing the two models for a long time, he started to do it.
"Now I directly hypothesize that when the coupling of electron density waves and spin density waves is considered, the ground state energy of the system is significantly reduced, and at the same time a stronger electron pairing interaction is formed near Fermi Surface..."
After completing the hypothesis, he shook his head with emotion. "Tsk, no matter what, I'm still not used to this kind of hypothesis."
Although he has made many important achievements in physics, he still recognizes his identity as a mathematician psychologically. However, certain methods in physics are quite difficult to recognize from a mathematical perspective.
It's like a joke: [Maybe mathematicians will be angry when they see this step, but we won't care about him].
This is what he is doing now. He will make assumptions first. Regardless of whether the assumption is correct or not, he will use it later.
After using it, go to the control experiment. As long as the experiment is correct, then the hypothesis is correct.
For mathematicians, it is like directly acquiescing that Riemann Hypothesis is correct. Of course, physicists sometimes actually acquiesce that Riemann Hypothesis is correct. This is mainly because mathematics can be infinite, but for physics, there is no true infinite, and the range of series that has been verified so far is enough for physicists to use, so Riemann Hypothesis has been used in many theories of physics, such as quantum chaos theory, Statistical Mechanics, random matrix theory, etc.
In short, mathematicians are like this. Physicists can use it directly after making assumptions, but mathematicians have a lot to consider.
Although Xiao Yi is still a little uncomfortable, once this method is used, it is still very satisfying.
Until the end.
"It's done..."
He looked in amazement at the integrated model that finally came out on the draft paper.
Its Hamiltonian is described as: [H=t∑[i, j],σ(ciσcjσ+h. c.)+∑iVini+J∑[i, j]SiSj+∑ihiSiz+x∑iniSiz]
where x is the coupling constant between electron density and spin density.
Probably, no one would have thought that these two theories, which were treated separately in the past, still have such a connection. Electron density waves and spin density waves can be coupled through interactions, thus forming a mechanism to enhance electron pairing.
And this model can roughly describe the mechanism of high-temperature superconductivity!
His heart was filled with excitement.
It is true that there is no way out despite the mountains and rivers, and there is another village with dark flowers and bright flowers.
Electron density waves and spin density waves have appeared in front of him countless times. Of course, they have also appeared in front of the entire physics community countless times. Probably no one can imagine that coupling between the two can occur!
"This new model... let's name it XSC theory for the time being."
Xiao's Superconductivity Theory.
With a slightly excited mood, he began to carefully examine the theory in front of him, and began to substitute various phenomena related to high-temperature superconductivity that he had previously listed into it to see if it could be explained.
And the final result is very gratifying.
Because they almost match!
But there are certain errors.
Of course, Xiao Yi still thinks it has errors as a mathematician.
That's another joke.
Mathematics Department: [0.9999... is not equal to 1.]
Department of Physics: [The experimental result is 0.999..., the calculation result is 1, I'm sorry, the theory and practice are so perfect, people won't say that I falsified the data, right?]
Department of Astrophysics: [The observation data is 1*10 raised to the 24th power, and the calculated result is 9*10 raised to the 24th power. Is it an order of magnitude? No problem then, this model is perfect.]
Therefore, in fact, the result of Xiao Yi, from a physical point of view, has almost perfectly explained high-temperature superconductors.
"So, I've got it?"
He was still a little confused.
It's probably like how Cooper accidentally developed Cooper pair after assuming that the total momentum of the two electrons was zero.
"Just get used to it, physics is like this."
He sighed slightly.
However, he knew clearly that this model could still be optimized, because although physics did not care much about a certain degree of error, in fact, according to his calculations just now, the error between the calculation results and those specific phenomena was still relatively large.
Among them, it may be mainly because of x, the coupling constant between electron density and spin density. Now it can also be called the Xiao Yi constant, or the superconducting constant.
Similar to Einstein constant and Planck constant.
According to the calculation results of Xiao Yi, this x≈1.271851 is obviously still somewhat inaccurate.
As for how to optimize, for him, there is a very simple method.
"Experiment! Data!"
As long as through more experiments and more data, he can easily get a more accurate value of x.
When he thought of this, he wished he could time travel to a year later and go to the already built Science Island Laboratory to conduct experiments.
But in the end, he shook his head.
"Forget it, it's better not to think so much."
"Go to School of Materials Science and borrow Sun Lina's laboratory... Well, okay, it should be Luo Mingya's laboratory."