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Thanks CTOnews.com netizen soft media new friend 1957189 clue delivery! This article comes from Weixin Official Accounts: Fanpu (ID: fanpu2019), authors: Dong Weiyuan, Liu Chao

In just a few days, three Chinese teams published relevant experimental results one after another, without exception, giving negative conclusions.

wrote an article| Dong Weiyuan, Lu Chao

Last week, Professor Ranga Dias of the University of Rochester, USA, broke the big news of achieving room temperature superconductivity at a conference (see "Is room temperature superconductivity reliable again?" Almost all professionals are cautious and even skeptical.

The next day, when Nature published Dias's paper online, some people immediately questioned its experimental data, arguing that the original data (left in the figure below) did not support the determination that the sample realized superconductivity at all, while the resistance data (right in the figure below) used in the paper was the "superconducting phase transition" obtained by unreasonably eliminating the so-called "environmental background factor below 220 K" curve. Of course, there are also DC and AC susceptibility data, which are processed in the same way as the team's previously retracted paper in Nature_minus a strange background that varies greatly between different measurements of the same sample. As for crystal structure, specific components, color changes and other factors, it always makes people feel that there are some "unconventional" factors. Especially in terms of color, from blue, superconducting to pink after pressurization, and then to red after pressurization, these are rare in high critical temperature superconducting materials. Generally, high critical temperature superconductors are all black, or even black and shiny.

However, this blog discussion cannot directly refute the paper. Fortunately, Professor Ranga Dias followed a very traditional and classical BCS theory. If the exact structure of the material is known, the critical temperature of the material can be predicted theoretically. This is a relatively mature field of research. Moreover, the experimental conditions published by Dias are not harsh at all. The pressure of 1 GPa can be easily achieved in ordinary superconducting research laboratories. It is not difficult to verify through real experiments. Sure enough, in just a few days after the publication of the paper, several teams in China published relevant experimental results one after another, without exception, giving negative conclusions.

Among them, Professor Wen Haihu of Nanjing University and his team directly repeated Ranga Dias 'material formula and experimental path, successfully obtained nitrogen-doped lutetium hydride (LuH2 ±xNy) material, placed it in a pressure environment of 1 GPa ~6GPa, and indeed saw some changes in resistance data at a temperature of about 300 K, but it seems to be a change in material structure, which may be identified as a phase transition, not a superconducting phase transition. But at all pressures, there is no evidence of superconductivity in the temperature range from 10 K to 320 K. Even from the trend below 100K, superconductivity is impossible below 6 GPa! Therefore, Ranga Dias claimed that the 1GPa pressure can achieve LuH2±xNy room temperature superconductivity, which must be very problematic. Either the experimental conditions were harsher, or the data interpretation was clearly wrong.

Wen Haihu's article title published on arXiv on March 15 and its abstract Second, the team of researchers from the Institute of Physics of the Chinese Academy of Sciences paid more attention to the distinctive color displayed by the samples displayed by Ranga Dias. Through experiments, they reproduced the dark blue lutetium hydride turning pink at about 2.2 GPa and turning bright red at about 4 GPa. This is very similar to the experimental results published by Ranga Dias team, which also shows that Ranga Dias team did use hydrogenated lutetium material, which also changed color under high pressure. However, Professor Cheng pressurized the material to 7.7 GPa and lowered the temperature to 1.5 K, and still did not see any signs of superconductivity. Of course, Cheng Jinguang's team's work was not doped with nitrogen, only color changes were seen, and no superconductivity was seen. Strictly speaking, it could not be regarded as a complete verification of Dias and others 'work. Special attention should be paid to the work of Professor Wen Haihu's team and did not see the change of material color under high pressure. Therefore, in Dias 'team's work, whether there is a direct connection between material color change and so-called "room temperature superconductivity" is still a big question mark.

Cheng Jinguang published the title of the article on arXiv on March 12 and its abstract. In fact, regarding lutetium hydride materials, it is estimated that many teams at home and abroad began to study them before Dias. After all, rare earth hydride synthesis at high pressure and high temperature and superconductivity at higher pressures has had a clear route since 2019. Moreover, in the past three or four years, scientists have long discovered a number of rare earth hydride superconductors, even alkaline earth metal hydride superconductors, but the superconducting temperature is high and low. Lu is the last rare earth metal of La series, which must have been tried by many research teams, but it has not been officially reported.

As early as March 9, Jin Changqing researcher team of Institute of Physics of Chinese Academy of Sciences took the lead in posting their own work in this field. It turns out that lutetium hydride is indeed a superconducting material, but it cannot be achieved at a pressure of only a few GPa, let alone room temperature superconductivity. Professor Jin Changqing's experimental results show that at a pressure of 218 GPa, the superconducting transition temperature of lutetium hydride is 71 K, and if the pressure is reduced to 181 GPa, the transition temperature will be reduced to 65 K. It should be reminded that the lutetium hydride superconductor discovered by Jin Changqing team has a molecular formula of Lu 4H23. The "hydrogen content" is much larger than LuH3-xNy published by Dias team. Perhaps this is the true situation of lutetium hydride superconducting materials.

As of the publication of Jin Changqing's article title and abstract published on arXiv on March 9, no duplicate results of Dias experiment published by international experimental teams have been found. however, the above-mentioned work of wen haihu and other three chinese scientists has basically falsified the so-called "room temperature superconductivity."

The big news that shocked the global physics community finally failed to withstand the "examination" of peers again. It can be said that scientific research needs to be serious and judgment needs to be cautious. Finally, to quote Luo Huiqian, a researcher at the Institute of Physics of the Chinese Academy of Sciences, he said: "The last 'C-S-H room temperature superconductivity' survived for 712 days and was forcibly withdrawn by the Nature Editorial Department. This time,'Lu-H-N near-atmospheric room temperature superconductivity' survived only 9 days and was basically falsified, indicating that the scientific community's ability to verify 'room temperature superconductivity' is rapidly improving. In the future, no matter who it is, if they want to announce big news like 'room temperature superconductor', they will definitely be more cautious. In short, room temperature superconductivity is still promising, but the future is still full of twists and turns. "

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