Shulou(Shulou.com)11/24 Report--

Room temperature superconductivity, which is considered to be the holy grail of condensed matter physics, is the research that can impact the Nobel Prize really coming? Recently, physicist Ranga Dias Diaz of the University of Rochester and his team claim to have created a new material that can achieve superconductivity at room temperature.

It was like a thunder blowing flat and shaking the physical circle. You know, if room temperature superconductivity can be realized and really move towards human life, then the whole world will change. Room temperature superconductivity will subvert energy technology, power transmission efficiency will be greatly improved, room temperature quantum computers, high-speed superconducting maglev, controllable nuclear fusion devices, super superconducting engines and so on will no longer be a dream.

However, to the outside world, researchers in the field of physics are very rational about this "explosive news". Luo Huiqian, a researcher at the Institute of Physics of the Chinese Academy of Sciences, said in a live broadcast of NetEase's science and technology that the reaction was relatively lacklustre. First of all, Diaz's report has already been communicated at a small meeting last year (2022), and a small number of people in the circle already know it; second, before this report, you have already seen the title and summary of the report, and you already know what he is going to say; more importantly, Diaz has done similar experiments before, and people are more likely to take a lively attitude to see if the experiment is credible or not.

You know, Diaz and his team have always been controversial: in 2020, Dias announced that it could achieve room temperature superconductivity and appeared on the cover of Nature. The results of the experiment were controversial in the next two years, and other laboratories tried repeatedly, but failed to reproduce the results. Therefore, physicists continue to question the rationality of the data results. In September 2022, Nature forcibly withdrew the manuscript despite the author's protest. The other was a paper published by Diaz as a postdoctoral student at Harvard, which also caused trouble when they announced that they had synthesized the first hydrogen metal material, which was published on Science, but after the paper was published, the team said the hydrogen sample had been destroyed due to operational error, and other research groups were unable to repeat the results.

Therefore, for the results of Diaz's experiment, the media also wrote: let the bullet fly for a while.

So, how long will it take to fly to know whether it is true or not? Luo Huiqian said that it may take several weeks or two months, of course, it may be faster, or there may be laboratories that will be able to complete the verification of the work.

Even if Diaz's experiment turns out to be correct, it is not necessarily a revolutionary technology to reshape the 21st century, as Diaz said. Luo Huiqian said that everyone need not be too excited, it is still a long way from revolutionary technology, and it is still a long way from the emergence of a new material to its large-scale use.

"if a superconducting material is to be used, the critical temperature, critical magnetic field and critical current density are all very important, and all three parameters must be high in order to have the basis for large-scale application." Luo Huiqian said, "in addition, if we want to do commercial use on a large scale, we have to face a lot of indicators, such as good mechanical properties, high chemical stability, material costs, and so on."

For room temperature superconductivity, the biggest obstacle comes from two aspects: one is that hydride superconductors predicted based on existing conventional BCS theory often need ultra-high pressure to achieve, and the technical challenge is too great; second, human understanding of the mechanism of unconventional superconductivity is still very imperfect, looking for new superconducting materials is often equivalent to blackening the eyes and doing things only based on their own feelings. Compared with the discovery of new materials of room temperature superconductivity, Luo Huiqian believes that being able to discover new phenomena and new physics, and finally help explain the mechanism of unconventional superconductivity is the most concern in basic science research, and can make an important contribution to the development of the whole physics framework.

For netizens, they may be more concerned about China's progress and status in superconductivity than Diaz's findings. Luo Huiqian said that China's basic research on superconductivity is basically in the forefront of the world and may not be the best yet, but we dare to say that China is already very good.

The following is part of the summary of Luo Huiqian, a researcher at the Institute of Physics of the Chinese Academy of Sciences, connected with NetEase through science and technology:

NetEase Science and Technology: recently, the United States Ranga Diaz (Ranga Dias) and his team claimed to have created a superconductor that can achieve superconductivity at room temperature. When you saw the news, what was your first impression?

Luo Huiqian: in fact, our reaction at that time was rather insipid. In fact, Ranga Diaz announced it at a small conference last year, but only a small part of the circle knew about it. Before this report, you can see the title and summary of his report, and you can guess what he is going to say.

In addition, Langa Diaz has also done some reports on the relevant system before, so everyone is more of a lively state, just want to see what it is, whether the experiment is credible, and so on.

NetEase science and technology: Diaz achieved 21 degrees Celsius + 10,000 atmospheric pressure, is this index a breakthrough? Does it make sense?

Luo Huiqian: Diaz has found a new material made of lutetium-nitrogen-hydrogen (Lu-N-H), which consists of three elements, and this route actually began around 2019. But the general rare earth lutetium + hydride to achieve superconductivity, at least hundreds of GPa, that is, millions of atmospheric pressure can be achieved. Therefore, if his work is accurate, it can be achieved at about 1GPa atmospheric pressure, which is much lower than a few hundred, but it still belongs to the category of high pressure. 1GPa is still a long way from normal pressure. For example, the maximum pressure on the earth is in the Mariana Trench, which is about 11000 meters deep, which is equivalent to 1100 atmospheric pressure and less than 10,000 atmospheric pressure, so the 10,000 atmospheric pressure is still very large.

NetEase Science and Technology: are there many physics teams repeating this experiment now?

Luo Huiqian: as far as I know, there must be many teams that can do it. Because in the past, superconductivity of such materials required to reach millions of atmospheric pressure, especially 4 million or even 5 million atmospheric pressure, few research institutes in the world can do such a thing. Because it is too challenging, it involves all aspects, experimental technology, experimental experience, experimental cost and so on are very important.

If today's 1GPa atmospheric pressure can achieve room temperature superconductivity, it means that many laboratories can achieve it, for example, many commercial high-pressure equipment can be achieved, these devices can easily reach 2-3 atmospheric pressure without any problem.

Therefore, in this case, if everyone follows his route, it should be very easy to achieve. Almost all superconducting laboratories can start verification work as long as they are willing to spend some money on equipment. But I don't know exactly who is doing the verification work.

On March 9 and March 14, arxiv posted two articles, both from the work of my colleagues, on the exploration of superconductivity of lutetium-hydride.

Strictly speaking, their work is not a verification of the Diaz experiment. Because the rare earth hydride route has been around since 2019, the industry has begun to work towards this route. That is, it is synthesized at high temperature and high pressure, and then go down to hundreds of atmospheric pressure to look for superconductivity. Moreover, the materials in both articles do not contain nitrogen.

If you take a closer look at the report of Diaz's experiment, you can find that although there are no specific parameters, you can see that the content of nitrogen is very high, rather than doping it in a little bit like the so-called before. If you look closely at its molecular structure, you can guess that the content of lutetium and hydrogen is basically close to 1:1, and the content is very high. In this case, it is not doped, but a synthetic new material. But whether there is such a structure or not is still a question. If we go in this direction, we will completely repeat his route.

NetEase Science and Technology: generally speaking, for physicists, how many times or how long does it take to prove the authenticity of this experiment?

Luo Huiqian: repetitive verification is very important. You cannot say that you have verified it once or twice, even if it has been repeated. First of all, you have to conduct repetitive experiments and publish them on this basis. Then, after the experimental conditions and scheme are made public, it is very important to be done according to the scheme, which can basically be done and verified.

For example, when hydrogen sulfide superconductor came out, the temperature was also very high, and 202 K was very amazing, because at that time, the highest recorded superconductor at high pressure, that is, copper oxide, was about 164 K or 165 K under high pressure. and then suddenly came more than 200 K, which is also a relatively shocking thing.

But at that time, the reaction of the industry to this matter was also very lacklustre, and it was not until a year later that it really became hot. This is a very interesting phenomenon. Why? Because at that time, after the hydrogen sulfide superconductor came out, although the paper was finally published, the quality of the data in the article was not good at the beginning, and everyone held a skeptical wait-and-see attitude, especially whether the results could be repeated.

After half a year, "Nature" specially sent a team of experts to the research group, requiring that all the experimental records can be passed and supplement the data of magnetic susceptibility. Although it was very difficult, it was finally added.

Another very important thing is that at that time, scientists from other countries repeated at least more than half of the results. For example, the data below 1 million atmospheric pressure were basically repeated. Further up, the experiment was relatively difficult, and the results were different, which basically verified its results.

It is only after a lot of repetitive results that people slowly accept this matter, so it takes a process.

NetEase Science and Technology: as you just mentioned, many scientists will repeat this experiment to infer the relevant ingredients. This time Diaz did not announce the relevant ingredients. Is this normal?

Luo Huiqian: I think this is the scientist's own freedom. We have often heard this kind of thing, and even some scientists will not give a specific formula when they submit a manuscript, but only give data, and then tell them what the specific material is after the paper is received. He has the right to do so. Of course, as a reviewer also has the right, if the author does not publish the specific formula, can choose to reject the manuscript. This is a two-sided judgment. Compared with the previous C-S-H 's work, this work not only gives the element composition, but also gives a general molecular formula and material structure, which can be regarded as a lot of information.

Generally speaking, in the case of very high pressure, it is normal to be confused about the structure of the material, and the result is really too much. The material itself forms a new structure in the process of pressing, and it may also decompose. After the decomposition, the materials with different structures are mixed together, so it is difficult to judge who is dominant in the emergence of superconductivity.

But the pressure of Diaz's experiment is not so high, only one 1GPa, in principle, no more than 100000 atmospheric pressure, measuring the structure is relatively easy, but it is not so easy to give the molecular formula immediately and accurately, which is the possible reason why there are two variables in his molecular formula.

NetEase Science and Technology: if the Diaz experiment is finally proved to be true, will it be a revolutionary technology to reshape the 21st century as Diaz said?

Luo Huiqian: I don't think we need to get too excited. Revolutionary technology is still a long way off. The emergence of a new material is very far away whether it can be used on a large scale.

So far, we have found at least 10,000 kinds of superconducting materials, or even more. We may have hundreds of thousands of inorganic materials, of which at least tens of thousands are superconducting materials. So superconducting materials are not that special. So far, we know that there are two types of high temperature superconductors, that is, superconducting materials whose critical temperature can exceed 40K. We have two types: copper oxide and iron-based superconducting materials. Of course, there are many kinds of materials in each category. This means that there can be many superconductors with high critical temperatures.

There are so many superconducting materials, but what are the materials that can be used on a large scale at the technical level? It was discovered about a few decades ago, mainly the so-called niobium-titanium alloy, and then further niobium, tin, niobium, germanium, and so on. Among so many materials, only a few were selected. Why? Because only these are particularly easy to use, although the superconducting temperature is below 9K, but the mechanical properties are particularly solid, other superconducting materials are not very easy to use.

For the new materials just discovered, it may not be used in most cases, because there are too many conditions and parameters involved.

To say the least, regardless of the material itself, it is assumed that Diaz's material can be found and repeated, and all the performance indicators are very good. But it should also be noted that the synthetic material is still under high pressure. The sample content in the diamond anvil is about the order of micrograms. If you want to apply it, it has to be at least in the order of tons, or even ten thousand tons. To do this kind of experiment, it may cost hundreds of thousands of yuan to get one milligram of material. How to use it?

NetEase Science and Technology: for superconductors, the room temperature condition is more important, or the high pressure condition is more important? Which is more difficult to achieve?

Luo Huiqian: it is true that the realization of pressure is a little more difficult. In fact, the question is understood this way: for superconducting materials, will the critical temperature be raised to room temperature, or can room temperature superconductivity be realized at atmospheric pressure? It must be the most difficult to reach room temperature superconductivity without any pressure.

High pressure does increase the superconducting temperature of superconducting materials, but it is not suitable for all materials. It is possible to lower the superconducting temperature for many materials, and it has both advantages and disadvantages. So it depends on what kind of materials you study.

NetEase Science and Technology: what are the main obstacles to the realization of room temperature superconductivity?

Luo Huiqian: the biggest obstacle to room temperature superconductivity should be the mechanism of superconductivity. I mentioned metal hydride superconductivity earlier. This kind of theory is ready-made, that is, BCS theory. The only challenge is experimental technology.

But for room temperature superconductivity, we hope to achieve it at atmospheric pressure without the help of high pressure, which is what we hope to see. But whether there is a theory in this area or not is a big question mark.

Because according to the traditional theory, the metal superconductor which satisfies the BCS theory can not exceed 40K, there is an upper limit, we call it conventional superconductor. But at present, many superconductors have temperatures higher than 40K, which we call high temperature superconductors, including high temperature superconductors, and some other superconductors below 40K, which can not be described by BCS theory. We collectively call them unconventional superconductors.

So is there any new theory to describe this matter? it is a pity that there is no such theory at present. So far, there is no suitable theory of unconventional superconductivity, let alone a suitable theory of unconventional room temperature superconductivity at atmospheric pressure. This is also a very important phenomenon of frontier exploration, that is, most of the time, experimental exploration is the first.

So I think the biggest obstacle is that our understanding of the existing mechanism of superconductivity is not perfect, far from perfect. Therefore, it is equivalent to a blackening of the eyes and doing things only according to their own feelings.

NetEase Science and Technology: some people say that whoever can win the room temperature superconductor will win the Nobel Prize, and will even be regarded as the third person in physics after Newton and Einstein. What do you think? If this result is verified, what invention can it compare with in the scientific community?

Luo Huiqian: this statement is a bit exaggerated. Any basic scientific research, including room temperature superconductivity, is a part of basic scientific research. Any basic scientific research is progressing bit by bit. Any theory, even Einstein's theory of relativity, cannot be an instant leap, not just a pat on the head. These great theories are slowly deduced from the ideas of our predecessors.

And it will take a long time for this new discovery to be accepted and considered meaningful. What's more, when we talk about room temperature superconductivity, it just shows that the temperature of superconductivity can be raised continuously.

There is almost no such thing in the history of science, so we don't have to get too excited and compare ourselves with Newton Einstein. Even if you go back to Newton, did you suddenly discover the theory of gravitation? in fact, it's not. in front of him, Galileo, Kepler, Hook and others have done a very detailed study of planetary orbits.

NetEase science and technology: now is the normal temperature (21 degrees Celsius), but also under the 1GP, the next high pressure drop to what extent can be commercial?

Luo Huiqian: at the very least, commercial businesses are faced with a problem, that is, they need this kind of output of more than one ton, and there is also the problem of the rate of finished products. The overall goal is to reduce costs. To put it simply, it is cost-effective, and the ratio of input to output is reasonable. The investment is lower and the performance is superior.

For superconductors, high pressure is absolutely not possible. The experimental cost of millions of atmospheric pressure is already so expensive that the diamond is crushed to make samples of micrograms. How can we make products of the order of tons? Even if the commercial equipment that reaches 20,000 to 30,000 atmospheres is about tens of thousands of yuan each, the output is still on the order of milligrams.

So we still hope that the pressure will be further reduced, for example, about dozens of atmospheric pressure will be easier. Just like everyone to pump up the bike, easily hit a few atmospheric pressure, there is no problem. But again, even if it is only 10 atmospheres, it is difficult to produce on the order of tons. Because most products in addition to high pressure, it is inevitable to use a high temperature, because the need for full chemical reaction of raw materials. This involves more practical problems.

NetEase Science and Technology: if room temperature superconductivity can be realized, how long will it take from laboratory to practical application?

Luo Huiqian: I have mentioned that if a superconducting material is to be used, the critical temperature, critical magnetic field and critical current density are all very important. All three parameters must be high in order to have the basis for large-scale application.

Industrialization we are facing is not the upper limit of the index, but the lower limit of the index. If you break the lower limit, it won't work very well. In the process of application, there will be relatively high requirements for the mechanical properties of the material, so it can not be used if it is exposed in space for a period of time, nor can it be unstable after several rounds of heating and cooling, and whether the material itself is expensive. Taken together, we believe that even if a room temperature superconductor at atmospheric pressure is found, all three critical parameters must be very good, and whether it can be used in a process estimated for decades is still not so optimistic.

NetEase Science and Technology: after the realization of room temperature superconductivity, what kind of change can it bring to our lives?

Luo Huiqian: if we find a material that is really perfect, and the various problem factors mentioned above have been solved. So, what are the places where superconductivity can be used in our lives?

Superconductors can be used everywhere we use electricity and magnetism. It is conceivable that if room temperature superconductivity is really realized at room temperature and atmospheric pressure, it may be possible to use it to weave a suspended cloud sofa, which is also very comfortable in the living room.

The simplest thing is that all kinds of electrical appliances will not heat up after using superconductors, mobile phones, computers and electric fans will not heat up, with low power consumption, high energy efficiency and power stability.

We can even imagine that the car does not need wheels, the train can be hung under the track, and it is OK without contact with the track. The spaceship also has a superconducting fusion engine with a near-infinite range.

In addition, we can make use of the good impedance of the superconductor, as well as itself as a macroscopic quantum phenomenon, we can manipulate and do some quantum operations to realize quantum computing.

Therefore, if room temperature superconductivity at atmospheric pressure can be realized in the future, it will certainly greatly change our lives.

NetEase Science and Technology: what is China's contribution to superconductivity? What is the current progress? What's your status?

Luo Huiqian: Chinese physicists have done very well in the field of superconductivity, especially in the basic research of superconductivity. In the 1980s, under very difficult conditions, the team represented by Zhao Zhongxian of our Institute of Physics discovered the superconducting material yttrium barium copper oxide in the liquid nitrogen temperature region.

In 2008, Chinese scientists made another major breakthrough in the field of high temperature superconductivity. Academician Zhao Zhongxian led a team to raise the critical temperature of iron-based superconductors to 55K and once again break through 40K, indicating that it belongs to a new family of high temperature superconductors and promotes the research of high temperature superconductors in China to be at the forefront of the world.

In the study of iron-based superconductivity, many new superconducting structural systems, or element systems, come from China. After having these high-quality samples, it is basically the Chinese who want to study its basic physical properties, and then use some means to study the properties of these materials for the first time.

Of course, the theoretical understanding of iron-based superconducting materials is also in the forefront of the Chinese people. So in 2009, Science published a report entitled "New superconductors push Chinese physicists to the forefront of the world."

I remember that at that time, international scientists were particularly eager to come to China for meetings and wanted to know how far we had come. With this drive, from 2008 to today, China's superconducting research has basically remained a leader in the world in some aspects.

Although China's basic scientific research as a whole still lags behind the international forefront, in some aspects, for example, we have discovered new superconducting materials, even if they are new materials that have just emerged in the world, their basic physical property research and understanding of the basic mechanism, most of the time, it was started by the Chinese, and it is the best that the Chinese have done, including applications.

For example, after the iron-based superconducting material came out, the first iron-based superconducting 100-meter wire was made by Ma Yanwei, a teacher from the Institute of Electrical Engineering of the Chinese Academy of Sciences. In fact, copper-based superconductivity has been going on for decades, and many companies in China have begun to do it on a large scale in the industrialization of copper-based superconductivity, so China's basic research on superconductivity is basically at the forefront of the world in all aspects. but perhaps the best level has not yet been achieved, but we dare say it is already very impressive.

NetEase Science and Technology: when do you think China can make a breakthrough in room temperature superconductivity?

Luo Huiqian: the next breakthrough in superconductivity actually has three aspects: one is new materials, looking for new superconducting materials; the second is new phenomena. In fact, the more important goal of new materials is whether we can see new phenomena. Then the new phenomenon will bring us a new understanding of the whole world. That is, whether the third can realize a new physics is actually the most concerned about doing basic scientific research.

Ordinary people may be concerned about the use of him, and we are most concerned about whether he will produce new physics. What does the new physics mean? That is to say, if you use the existing theoretical framework of physics, the most basic concepts, to understand new phenomena, you will find that you cannot understand them.

In fact, this is the biggest revelation that superconductivity has brought to us. Many so-called unconventional superconductors were discovered in the 1970s and 1980s, which so far cannot be understood, that is, many new phenomena have emerged. this means a new physics in it. This is the challenge to the basic theory of physics. If the theory of unconventional superconductivity can be established, it will be a great contribution to the whole framework of physics.

NetEase Science and Technology: you have a book, Superconducting tiny Times, which is very interesting, ha. It divides the development of superconductivity into several ages. Room temperature superconductivity is divided into the "Yunmeng era". Does the development of superconductivity come to an end in the Yunmeng era? What kind of imagination will this cloud dream era bring us?

Luo Huiqian: I hope it is not a climax, because we have just begun this era.

My book also dates back to different times: in the age of enlightenment, people feared and understood nature, from ordinary electromagnetic phenomena to the internal structure and mechanism of matter.

In the stone age, the superconducting phenomenon was discovered, alchemy stir-frying plus 18 martial arts, a preliminary understanding of this magical physical phenomenon.

In the Aoki era, the explosion of superconducting materials, a variety of new superconducting materials, not impossible, only unexpected.

In the black copper age, high temperature superconductivity was born, and the pearl in the crown of physics is so dazzling, complicated and exciting.

In the age of white iron, iron-based superconductors accidentally discovered that the superconducting family was unprecedentedly prosperous, and the unconventional superconducting mechanism seemed to be within reach.

In the Yunmeng era, room temperature superconductivity may be possible, new superconducting materials are springing up like bamboo shoots after a spring rain, and the study of superconducting mechanism continues to bring importance, which is as beautiful as a dream.

We don't know how many years this era can last, and we don't know if there is another era. However, the discoveries of scientific research, especially basic scientific research, are always full of surprises and can always emerge inadvertently. Therefore, we must maintain enthusiasm and attention to basic scientific research. This is very important, do not follow the big news of room temperature superconductivity today, tomorrow will not pay attention to us.

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