Source: titanium media
Author: Lin Zhijia

After nuclear fusion and ChatGPT, new technological breakthroughs have been ushered in in the field of room temperature superconductivity.

According to the website of the American physical Society (APS), Ranga Dias, an assistant professor at the University of Rochester, a researcher in the Department of Physics at Harvard University, and a condensed matter physicist, announced the latest research results at the "static superconducting experiment" report meeting held on March 7, local time.

Through experiments, Diaz's team created a "superconductor" that can work under actual conditions (Practical conditions) at room temperature and relatively low pressure. The superconductor is a mixture of hydrogen, nitrogen and lutetium (Lu-N-H) and pressurized in a "diamond anvil" device. It enters the superconducting state at a temperature of about 21 ℃ and a pressure of 10 000 standard atmospheric pressure, thus losing its resistance to current, thus realizing the possibility of the application of this new type of superconductor at room temperature.(note: humans have been able to synthesize diamonds at 50,000 to 60,000 atmospheres.)

Meanwhile, in the early morning of March 9, the study was published in the British journal Nature entitled "evidence of near-environmental superconductivity in N-doped lutetium hydride".The time stamp shows that the paper was submitted in August 2022 and was accepted by Nature on January 18 this year.

This means that in the future, under conventional conditions, this kind of "superconductor" is expected to be used in many scenarios, such as aircraft, quantum computers, maglev transportation, superconducting medicine, nuclear fusion reactor "magnetic seal", superconducting gravity simulation and so on. Mankind is one step closer to the long-standing goal of creating an optimal efficient power system.

It can be predicted that once the room temperature superconductor technology is mature and applied, a new technological era of high-efficiency machines, ultra-sensitive instruments and revolutionary electronic products is coming, which may lead to a new energy revolution.

The news spread, the world is in hot discussion, related issues have directly rushed to the first hot search Zhihu Inc., Reddit topic is also rising.

"this is the beginning of new materials that can be used in practical applications," says Mr Diaz, a revolutionary technology that will reshape the 21st century. With this technology, mankind will enter a superconducting society, and you will no longer need things like batteries, which "can definitely change the world as we know it."

However, a similar paper published by the team in October 2020 was questioned, which eventually led to the withdrawal of the British journal Nature, suggesting that Diaz's new research is still likely to face skepticism from academics. ScienceNews, a biweekly science magazine, believes that the study is likely to be subject to very close scrutiny.

Subsequently, Ranga Dias told the media on March 9 that he had repeated the experiment many times, had the confidence to review it, and was confident of his team's new discovery, but he also pointed out that "it will take several years of hard work to apply our discovery of new materials for room temperature superconductivity to the real world of any scale."

Wang Li (a pseudonym), a domestic university physics professor, told titanium media App that the experimental results are far more meaningful to condensed matter physics than the practical technology of superconductivity, and it has found a new way to find high temperature superconducting materials. Another industry source said, "High pressure room temperature superconductivity is very difficult to commercialize."

From the perspective of the capital market, as of press time, the "superconducting" sector stocks collectively opened higher. Yongding shares, Bailey Electric and Falsheng rose by the daily limit, Baosheng shares, Western Superconductor and Western Materials rose by more than 5%, while Dongfang Tanye, Lianchuang Optoelectronics and Han Cable shares rose.

So, will the "room temperature superconductivity" mentioned by the team of American scientists be recognized by the scientific community this time?

A century's road to the study of superconductivity

For more than a century, room temperature superconductivity has been a research hotspot in the field of material science.

Literally, superconductivity means super conductivity.

According to their electrical conductivity, substances can be divided into conductors, semiconductors and insulators. Among them, there are a large number of charged particles which can move freely in the conductor, and they can move freely under the action of external electric field to form electric current.

A superconductor has zero resistance at a certain temperature (defined as superconducting critical temperature). Although zero resistance in the strict sense cannot be measured, many experiments show that the resistivity of superconducting materials is 10 orders of magnitude lower than that of the metals with the best conductivity, such as silver, copper, gold, aluminum and so on.

This means that the current of 1A induced in a closed superconducting coil takes nearly 100 billion years to attenuate, longer than the age of 13.8 billion years in our universe. Therefore, we have good reason to think that the resistance in the superconducting state is zero.

In 1911, Dutch physicist Heike Kamerlingh Onnes discovered that when mercury is cooled to-269C, the resistance suddenly disappears and electrons move unhindered in it. Later, he noticed that many metals and alloys had properties similar to mercury, and he called this special conductivity "superconducting state"-the first time that superconductivity had been discovered.

Onness won the 1913 Nobel Prize in Physics for studying the properties of matter at low temperatures and producing liquid helium.

For more than a century since then, new superconducting materials have been discovered one after another, hitting the higher critical transition temperature of superconductivity one after another, and each discovery has prompted scientists to devote themselves to the related research upsurge:

• In 1957, the first BCS theory which can really describe the phenomenon of superconductivity was born, which was established by American scientists John Bardeen, Leon Cooper and John Schrieffer based on "wave-particle duality". They believe that when there is a voltage, the free electrons in the outer layer of the metal will flow through the lattice to form an electric current, but usually the lattice is defective and the current will be hindered by thermal vibration.

• In 1986, Berenoz and Mueller of IBM Company in Zurich, Switzerland, discovered 35K superconductivity in the copper oxide system.

• In February 2008, Japanese scientists discovered the existence of 26K superconductivity in iron arsenide system.

• Thanks to the efforts of Chinese scientists, the superconducting critical temperature of this kind of materials soon exceeded 40K, and the high temperature superconductivity of 55K was achieved in bulk materials. The superconductors above 40K are also called high temperature superconductors, copper oxide and iron-based superconductors, which are the only two families of high temperature superconductors.

• In 2016, E. Gregoryanz of the University of Edinburgh and others obtained a "new solid state" of hydrogen at 325 GPa, which they thought might be metal hydrogen. The paper was published in the journal Nature.

• In June of the same year, German scientists posted a paper on the presence of 350K superconductivity in graphite crystals on arXiv, with samples from graphite crystals from a Brazilian mine. However, in theory, whether there is room temperature superconductivity in graphene has always been a focus of controversy, and the "superconducting evidence" in this paper is that there is a slight decrease in resistance at 350K and will respond to the change of magnetic field. Experts believe that this may have little to do with superconductivity.

• In 2017, the Harvard University research team announced that metal hydrogen had been achieved at 495 GPa. They observed the increasing pressure of hydrogen, from transparent molecular solids to black opaque semiconductor hydrogen, and finally to metal hydrogen with metal reflection. The paper is published in the journal Science.

Strictly speaking, to judge whether a material is a superconductor, there must be two independent electromagnetic characteristic criteria: 1. Whether it has absolute zero resistance; 2. Whether it has complete diamagnetism. The latter was discovered by the German scientist Walther Meissner Meissner, also known as the "Meissner effect", that is, the superconductor has "complete diamagnetism" under the magnetic field, and its internal magnetic induction B is zero.

Superconductors are of great significance to people's production and life.In fact, the application of electronic technology is based on resistive circuits, and a large amount of energy is converted into a waste of heat because of the resistance of ordinary conductors. The realization of room temperature superconductivity is expected to make electrical energy rarely converted into heat, thus improving the efficiency of conductors and devices, greatly promoting the development of existing electronic technology, so that more fine electronic components can be applied to human life.

Luo Huiqian of the Institute of Physics of the Chinese Academy of Sciences mentioned in an article that superconducting transmission can save about 15% of the loss in current high-voltage AC transmission technology. Superconducting transformers, generators, motors, current limiters and energy storage systems can achieve efficient power grids and motors. The superconducting magnet made of superconducting coil has the advantages of light volume, high magnetic field, good uniformity and low energy consumption. it is the core of key technologies such as high resolution nuclear magnetic resonance imaging, basic scientific research, artificial controllable nuclear fusion and so on.

Maglev trains take advantage of superconductors. The superconducting coil can carry a large current and become a powerful superconducting magnet. The train and the track are equipped with superconducting magnets respectively. When there is an external magnetic field, due to complete diamagnetism, an opposite magnetic field is produced inside the superconductor, so that the total magnetic induction inside the superconductor is zero. The resulting repulsion can levitate a heavy train in the air. By changing the orientation of the magnetic field on the track, the train can keep moving forward.

On November 27 last year, "room temperature superconductivity" was selected as the "Top Ten basic Research keywords" in 2022.

There is a lot of controversy among the researchers of room temperature superconductivity.

Before Diaz's study, the highest temperature of superconducting materials was achieved in 2019 by German scientists in a laboratory at the Max Planck Institute of Chemistry and in collaboration with Russell Helmley's research team at the University of Illinois in the United States. The researchers used lanthanum (a metal rare earth element La) superhydride to achieve a superconducting transition temperature of-23 degrees Celsius at 1.7 million atmospheric pressure.

As early as 1968, Neil Ashcroft, a theoretical physicist at Cornell University in the United States, theoretically predicted that pure hydrogen could conduct superconductors at room temperature, because metallic hydrogen would have a higher critical temperature of superconductivity, only requiring a pressure of 5 million times atmospheric pressure. He proposed in 2004 that hydrogen-rich compounds, such as methane, methylsilane and ammonia, require much lower pressure than metallic hydrogen to become superconductors at high critical temperatures.

Unfortunately, the experiment was disappointing and there was a big gap between the experiment and Ashcroft's prediction.

As the most abundant element in the universe, hydrogen is also a promising element. To obtain high temperature superconductors, stronger chemical bonds and lighter elements are needed. Hydrogen is the lightest material, and hydrogen bond is one of the strongest chemical bonds. Theoretically, solid metal hydrogen has high Debye temperature (an important physical quantity of solids) and strong electron-phonon coupling, which is necessary for room temperature superconductivity.

However, just converting pure hydrogen to a metal state requires a very high pressure. In 2017, Isaac Silvera, a professor at Harvard University in the United States, worked with Diaz, who was doing postdoctoral research in his laboratory, to achieve this goal for the first time in the laboratory.

After that, however, Diaz's road to research was not so smooth.

On October 14, 2020, the British magazine Nature published a cover paper on the first realization of "room temperature superconductivity" which caused a sensation.Diaz's team created a ternary hydride (C-S-H) that achieved superconductivity at a transition temperature of 15 degrees Celsius at 2.67 million ultra-high atmospheric pressures, that is, the phenomenon of superconductivity at room temperature was observed. Only two months after the contribution, it appeared on the cover of Nature magazine and was praised as a Nobel Prize-level job.

Diaz claimed that this is the first time that superconductivity has been observed at room temperature. Their findings will provide the possibility for many potential applications. But although they have solved the temperature barrier, they have the problem of high pressure-2.67 million atmospheric pressure, which is very close to the pressure at the center of the earth at 3 million atmospheric pressure. With such a high pressure, only a few laboratories in the world can achieve it-which lays the groundwork for the subsequent "withdrawal" incident.

At that time, American academic circles were generally optimistic about this experiment. Brian Maple (Merrill Maple), a professor of physics at the University of California, San Diego, commented: "this study inspired people to think about the relationship between conventional superconductors and high temperature superconductors, the mechanism of superconducting electron pairing, the direction of looking for new materials in the future, and the new fields of the application of superconducting technology, and described a better future for mankind."

However, some researchers believe that Diaz's experimental conditions are very extreme, which means that the practical application is still very far away. Diaz and others created a company called extraordinary Materials to commercialize room temperature superconductors as soon as possible.

But Diaz's research can not be repeated, in fact, it is the biggest gap in the industry. Diaz later said he accidentally broke the diamond in the course of the experiment and did not repeat the experiment. However, there are still several international research groups that can do the near-500GPa high-pressure technology, but Diaz did not repeat the experimental results of metal hydrogen.

What is even more incredible is that one of the key evidence of this paper, that is, the hydrogen metal in the diamond anvil, was taken with an iPhone camera and appears to be extremely unprofessional. Later, under repeated questioning, Diaz admitted that the success rate of the "metal hydrogen" experiment was not high, and he may have obtained "effective" experimental data only once or twice. Scientists have reason to suspect that the resulting "metal reflection" signal may come from the metal gasket in the high-pressure cavity, rather than the metal hydrogen itself, and the author later published an article correcting the photoconductivity data. Therefore, whether metallic hydrogen can really achieve room temperature superconductivity has become an unsolved mystery.

In the face of collective skepticism by scientists, the editorial department of the British journal Nature withdrew the paper on September 26, 2022, after all the authors did not agree to withdraw the paper.

According to Nature, this paper uses a non-standardized, user-defined program in some key data processing steps. Specifically, this program refers to the background subtraction used in the paper to process the original data to generate the magnetic susceptibility map (the method used to deal with noisy background signals). The processed data subtraction is not explained in the paper, so the validity of the data is also questioned, which will weaken the confidence of the outside world in the magnetic susceptibility data.

On the same day, the top journal Science reported in depth on the withdrawal and interviewed several parties involved in the incident. The title of the report directly quoted the original saying of the scientist: "Something is seriously wrong" (the matter is very serious).

Less than half a year later, Diaz is making a comeback with the new / other ternary hydride lutetium-nitrogen-hydrogen (N-Lu-H) (formerly hydrogen-sulfur-carbon).Under the less extreme high pressure of 1GPa, a higher superconducting transition temperature of 21 degrees Celsius is achieved-the pressure is lower, and the superconducting critical transition temperature (Tc) is higher.

In the nearly 15-minute speech, Diaz repeatedly gave a detailed account of room temperature superconductivity. However, a paper published in the journal Nature on March 9 also admitted that although the results are beyond imagination, further experiments and simulations are needed to determine the exact stoichiometry of hydrogen and nitrogen and their respective atomic positions. in order to understand the superconducting state of the material.

At the site of the release of the latest results in Las Vegas, the small lecture hall was packed with physics bulls. These include Professor Paul Chu, a pioneer in high temperature superconductivity, and Dirk van der Marel, a condensed matter physicist at the University of Geneva who has been questioning room temperature superconductivity. Outside the lecture hall, it is crowded with a large number of physics researchers who were unable to enter, so that security guards need to constantly disperse the crowd to prevent fire hazards.

But ScienceNews, a biweekly science magazine, believes that the study is likely to be subject to very rigorous peer review, especially with regard to reproducibility.

There is hope for "room temperature superconductivity", but doubts remain.

Following the fusion ignition and "net energy gain" (Q > 1) achieved by Lawrence Livermore National Laboratory in California in December last year, and the artificial intelligence chat model ChatGPT released by OpenAI, American scientists successfully dropped another "nuclear bomb" in the field of physics this time.

(for details, see the previous article of the titanium media App: "China and the United States" fierce battle, "Nuclear Fusion", "ChatGPT killed madness, detonated a new track worth hundreds of billions of dollars in two months")

At present, although the outside world is shocked by the experiment, the industry is more in a "wait-and-see" mood in view of Diaz's previous controversy.

Milei, founding partner of China Science and Technology founder Star, told titanium media App: "Last year, I thought that superconductivity in the energy field is semiconductors in the information field. The information revolution in the past 60 years depends on the breakthroughs in semiconductor materials, and the energy revolution in the next 60 years depends on the breakthroughs in superconducting materials. So last year we began to make great efforts to lay out the direction of high-temperature superconducting materials, and now we have invested in three upstream and downstream companies of high-temperature superconducting materials, with an investment of more than 100 million yuan. I just didn't expect that this direction will become popular again so soon. "

Luo Huiqian said in a live broadcast at the Institute of Physics of the Chinese Academy of Sciences on the evening of March 8 that the atmospheric pressure of about 10, 000 atmospheric pressure in this study is much lower than that of the previous 200GPa, and that the experiment is likely to be reused. For example, specific heat measurements have rarely been done to verify superconducting transitions because the pressure is too high to do so, and this 1GPa makes specific heat measurements possible.

Researcher Ji Yanjiang believes that although it is difficult to measure complete diamagnetism (Meissner effect) experimentally, he thinks there is a lack of evidence for Diaz's deliberate fraud.

A scholar in the quantum field told the titanium media App that at present, quantum computing still has to be ultra-low temperature, and room temperature superconductivity is still very difficult to achieve. Other physicists believe that whether it is room temperature superconductivity or high temperature superconductivity, temperature is only an index to measure the application of superconductors. at present, niobium-titanium alloy superconductors are still widely used, and this kind of room temperature superconductivity is difficult to be used in a short time.

A Zhihu Inc. respondent said that for this kind of research, it is best to wait for the results of peers to reproduce. He believes that the result is still the result of one family's opinion, not the result of peer review.

Jin Changqing of the Institute of Physics of the Chinese Academy of Sciences and David Seperly of the University of Illinois at Urbana-Champaign jointly wrote in the journal Nature that the author's findings will undoubtedly be controversial because they are almost twice as high as other cyanide with high-temperature superconductivity. it also shows that there is relatively little hydrogen in the paper samples compared with similar superconducting compounds. If nitrogen doping is indeed part of the reason for the superconducting state, its role in achieving such a high transition temperature remains to be determined.

"regardless of the mechanism, the prospect of superconducting materials under environmental conditions is attractive. Superconducting materials can make powerful magnets, such as magnetic resonance imaging (MRI)-a technology that has had a profound impact on medical diagnosis since it first appeared half a century ago, and can also be used as a levitation object to inspire the idea of maglev trains. But standard MRI systems currently require expensive cooling without high temperature superconducting components, so maybe this study of new hydride compounds will bring us closer to these technologies. " Jin Changqing and Sepeli jointly said.

So, as to whether the Holy Grail of room temperature superconductivity is going to come to an end this time, more people think that it is necessary to let the bullet fly a little longer.

Edit / jayden