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

This article comes from the official account of Wechat: back to Park (ID:fanpu2019), by Dong Weiyuan and Tan Ying

On March 7, US time, at the March meeting of the American physical Society, a grand event in the international physics community, Professor Ranga Dias of the University of Rochester announced that room temperature superconductivity has been achieved at near ambient pressure (nearly 10,000 atmospheric pressure). The title of its report is: Observation of Room Temperature Superconductivity in Hydride at Near Ambient Pressure. As soon as the news came out, swiping the screen quickly showed concern not only to the academic community, but also to the industrial community. If the experiment can be verified repeatedly in the end, it will be an explosive breakthrough with extensive influence.

Written by Dong Weiyuan, Tan Ying

Yesterday (March 8), a piece of news about superconductivity was all over the Internet, and even WeChat groups, which are usually keen on health preservation and food, suddenly changed their style and began to pay close attention to an academic conference on physics held as far away as Las Vegas in the United States. At the annual meeting of the American physical Society (APS), Professor Ranga Dias of the University of Rochester reported the astonishing latest achievement: room temperature superconductivity of 21 ℃ (294K) above zero at 1GPa pressure! According to the news and pictures sent back from the scene, the inside and outside of the venue were once packed and exceeded the security requirements, and the security guards struggled to drive away the crowd.

Professor RangaDias reports on the scene | the picture is from the Internet. Why do you say "again"? As early as 28 months ago, in October 2020, Professor Ranga Dias and his team published the discovery of room temperature superconductivity in hydrocarbon sulfide (C-H-S) in the journal Nature. The achievement at that time was to achieve superconductivity of 15 ℃ under the pressure of 267GPa. This achievement attracted a lot of social attention at that time, and we also wrote a theoretical introduction (see "realizing room temperature superconductivity for the first time under ultra-high pressure" for details).

Unfortunately, the 2020 paper was later questioned and was forcibly withdrawn by the journal in the face of the author's opposition. This new achievement is based on ternary hydride (N-Lu-H), specifically nitrogen-doped lutetium hydride (nitrogen-doped lutetium hydride, NDLH). Whether its conclusion can finally be accepted by the academic community needs to be repeated by other experimental groups.

Science's report on the withdrawal of the above article in 2022 before the paper went online, A, a superconducting scientist who spoke on condition of anonymity, told Guipu that he had an intuition that the result was "too good to be true." he said that some people had predicted the result with the traditional BCS theory before, but the key point was that the material was difficult to achieve, and now Ranga Dias magically worked it out.

Sun Liling, a researcher at the Institute of Physics of the Chinese Academy of Sciences, said in an interview with Huipu: "it is worth noting that the sample photos given in the Dias report are blue, which is completely different from the black and brown superconductors we usually see. If its color is the true color of the sample, it means that even if other research groups can prove its superconductivity experimentally in the future, this kind of superconductor should not be the superconductor we used to know. "

In a screenshot of the experimental video given in Dias's latest paper, the sample is blue under environmental pressure. "people expect this to be verified by other experimental research groups," she said. Just like the upsurge caused by the discovery of copper oxide superconductors and the report that the superconducting transition temperature broke through the liquid nitrogen temperature region at the American APS meeting in March 1987, people had a definite understanding of the superconductivity of copper oxides through a large number of experimental studies in a very short time, which made Mueller and Bannoz, the discoverers of copper oxide superconductors, won the Nobel Prize in Physics that year. "

This is sensational because if this experiment is approved, it will undoubtedly be a commercially valuable achievement, which is much more important than the own achievement in 2020. The result of two and a half years ago, even if it was true, required a pressure of 2.7 million standard atmospheric pressure, which is almost close to the pressure at the center of the earth, which is beyond the reach of modern technology. Professor Ranga Dias now claims that room temperature superconductivity is achieved at 10, 000 standard atmospheric pressure, which makes the process much less difficult. This is only 10 times the natural pressure of the sea water at the Mariana Trench, or at the junction of the crust and mantle.

"the newly reported superconductors can be obtained at very low pressure (1GPa), which can be easily achieved on commercial experimental equipment (usually < 3GPa), and there are no barriers to experimental technology," Sun said. "

Professor Ranga Dias did not disclose many details of the experiment at the APS lecture, but the work was published online by Nature on the evening of March 8, Beijing time. "Professor Dias has given the preparation method and general chemical composition in his newly published Nature article, so other research groups should be able to confirm the reliability of their experimental results in a short period of time," Sun said.

Luo Huiqian, a researcher at the Institute of Physics of the Chinese Academy of Sciences, also told Huipu: "A lot of experimental data and videos have been published, and the conditions are very general and can be easily repeated."

The article has just been published online by Nature under such friendly experimental conditions that it makes people feel that if it can be proved to be true, it can be applied to various industrial and even life scenarios in minutes. No wonder many business people who did not care about physics inquired carefully about the reliability of this achievement at the first time, and some business experts even wanted to catch up on the theoretical knowledge of superconductivity.

In the eyes of outsiders, physics is a knowledge that pays great attention to principle models and theoretical calculations. Theoretical physicists also often refer to the "abnormal magnetic moment of electrons" as an old stem to demonstrate the spirit of physics. The theoretical predicted value of this physical quantity is consistent with the experimental measured value in at least 12 significant digits, which is the constant with the highest confirmation accuracy.

However, the research status of superconducting physics is difficult to reflect this glory. In fact, superconducting physics is more like a metaphysics than particle physics. The researchers tried all kinds of possible materials almost like looking for a needle in a haystack through a jumble of hazy clues.

At present, a variety of materials with superconductivity have been found, including metallic elements, metal-containing compounds, non-metallic elements, non-metallic compounds. Many materials are completely insulated ceramics under ordinary conditions and exhibit superconducting properties only in very special environments. Of course, this fully shows that the superconducting phenomenon is a universal characteristic, which is not limited to specific elements or material types.

However, the more common the characteristics are, the deeper the underlying principles are often hidden. Since the superconducting phenomenon was first discovered in 1911, theoretical researchers have tried to make a theoretical explanation for this magical phenomenon. Now, more than 100 years later, physicists have indeed put forward many theories.

But each theory can only explain part of the superconducting phenomenon. at present, there is no unified theory that can explain all the superconducting properties. We only know that superconductivity, like superfluid, is the display of quantum effects in the macro world, but the underlying elements that limit the triggering mechanisms, methods and conditions are always difficult to capture.

If you want to judge the flammability of a material, you only need to simply calculate the binding energy of the chemical bond on the computer to make the judgment directly, instead of actually lighting it with a match. This is precisely because we understand the underlying elements of the feature of "combustion". As far as superconductivity is concerned, our understanding is far from this.

In fact, the whole academic circle is also very much looking forward to the establishment of the theory of superconductivity, which can be seen from the distribution of Nobel prizes. Almost every important achievement in the study of superconductivity is particularly favored by the Nobel Prize Committee. so far, five Nobel Prizes have been awarded to the field of superconductivity, namely 1913 (the first discovery of superconductivity), 1972 (BCS theory), 1973 (Josephson effect), 1987 (superconductivity of ceramic materials) and 2003 (new theory of superconductivity and superfluid).

Among the three winners in 1972, John Bardeen is the only physicist in history to have won the Nobel Prize twice. He won the Nobel Prize in 1956 for inventing the transistor. You know, even Einstein won the Nobel Prize only once for explaining the photoelectric effect, and his theory of special relativity and general relativity never won him a second time. Thus it can be seen how much the Nobel Prize Committee recognizes the emergence of BCS theory.

However, even a theory such as BCS theory, which has been written into textbooks, can only explain a small part of the superconductivity that has been discovered. Interestingly, the phenomenon of superconductivity in the mouth of professionals is divided into two categories: "conventional superconductivity" and "unconventional superconductivity". The so-called unconventional superconductivity refers to those superconducting phenomena that can not be explained by BCS theory. For example, graphene, which was very hot a few years ago, is a typical unconventional superconductor.

Professor A, the aforementioned superconducting expert, said that if the discovery can eventually be repeated and verified to be true, its theoretical explanation is still the traditional BCS. In theory, there is not much new to do, and the difficulty lies in how to realize the material. When asked whether the emerging AI aided design materials can stand up to the task, he said that it is very difficult, because the computer has greater limitations, and what is easy to do is the traditional weak correlation materials. The physical mechanism of these materials is clear, which is equivalent to changing the parameters, but the computer can do nothing about the strong correlation materials.

In the process of exploring the superconducting phenomenon, theoretical researchers think hard, while experimental researchers rely on intuition, experience, creativity, courage, patience and luck. "return to Park" will continue to follow the follow-up progress of this matter, and will continue to invite professionals to interpret it tomorrow. Please look forward to it.

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