The sample has been accused of defects, and the South Korean team's room temperature superconductivity has ushered in a new era of humanity? Submit two research papers within 3 hours | Team | New Era

The suspicion of room temperature superconductivity research by the Ranga Dias team at the University of Rochester in the United States has not dissipated, and researchers from teams such as the Korean Quantum Energy Research Center and Goryeo University have once again made a "peer-reviewed" move. The research team announced the successful synthesis of the world's first room temperature and atmospheric pressure superconductor, which is a modified lead apatite that can exhibit superconductivity below 127 ℃ under atmospheric pressure conditions.

Given the challenges and importance of room temperature superconductivity research, such heavyweights have always sparked widespread attention and discussion. The research team commented on the study and stated, "We believe that our new developments will be a new historical event that opens up a new era for humanity.". However, just like the previous Dias team's research, this Korean team's research will also be tested by time.

What makes the event even more confusing is that the new research mentioned above is actually related to two papers. From a timeline perspective, the first paper was submitted at 7:51 am on July 22nd, and the second paper was submitted at 10:11 am on July 22nd. The two papers with a submission time difference of less than 2.5 hours were both published in the preprint system arXiv and have not yet undergone peer review.

The number of authors in the two articles is different, but there are two overlapping authors. From the content of the paper itself, the second one is more detailed. One of the authors of the second paper mentioned above, Hyun Tak Kim, a physics professor at William and Mary College in the United States, directly stated in an interview that there were "many flaws" in the first paper and it was uploaded without his permission.

When did superconductivity become "grounded" in the past century

More than 100 years ago, Dutch physicist Hennes opened the door to superconductivity for humanity. In 1911, Onnes discovered in his research that when the temperature dropped below 4.2K, the resistance of metallic mercury suddenly dropped to zero, which was not caused by any experimental errors.

From then on, mercury became the first superconductor discovered by scientists, with a superconducting Tc of 4.2K. The so-called superconducting Tc refers to the superconducting transition temperature, which is the temperature at which a superconductor enters the superconducting state from a normal state.

Overall, zero resistance is one of the fundamental characteristics of superconductors, and another important fundamental feature is the Meisner effect. After more than 20 years of Onnes's discovery, Meisner discovered in his research and measurement that when a material is in a superconducting state, its internal magnetic field is zero, exhibiting complete diamagnetism, which is also known as the Meisner effect.

The discovery of superconductivity is considered one of the greatest inventions of the 20th century. However, until now, the practical application of superconductors has been limited to a few specific scenarios such as magnetic levitation. The South Korean research team also mentioned that since Annes discovered superconductivity, scientists have been searching for room temperature superconductors.

The reason is not difficult to understand. The extremely low superconducting Tc that maintains material superconductivity is a great obstacle for large-scale application development.

Scientists have made some significant achievements on this path of improvement and breakthrough. In the 1980s, the discovery of copper based superconductors brought superconducting Tc to over 40K; After entering the 21st century, scientists from Japan, China, and other countries have further improved superconducting Tc on iron-based superconductors.

The South Korean team also cited the controversial research of the Dias team in the paper, which proposed a superconductor composed of hydrogen, nitrogen, and lutetium, which can achieve room temperature superconductivity of about 294K at approximately 10kbar.

Zhu Jingwu, a pioneer and renowned physicist in the field of international high-temperature superconductivity research, stated in a media interview in March this year that in the past, we thought that reaching a liquid nitrogen temperature above 77K could be applied, but when preparing materials, we found difficulties and the cost was too expensive. Later, after overcoming the temperature and reaching room temperature, it was discovered that a very high pressure needed to be applied, which caused another problem.

It can be said that in the past 100 years, the field of superconductivity has always been on the path of continuous exploration. A path points towards superconducting Tc, bringing it infinitely close to the room temperature that is convenient for practical applications; Another path lies in continuously delving deeper into the mechanisms behind superconductivity.

The Korean version of room temperature and atmospheric pressure superconductors, the real breakthrough is still "the wolf"

Compared to the achievements of the Dias team more than three months ago, the superconductors of the Korean team are even more incredible. Not only does it solve the temperature problem, their LK-99 doesn't even require a "high-pressure assistant". The Tc at 127 ℃ not only significantly improves its numerical performance compared to previous studies, but more importantly, it means that its applicable temperature range is greatly expanded.

How to obtain LK-99? The second, more detailed paper above shows that the research team synthesized LK-99 using solid-phase method, using lead oxide, lead sulfate, copper, and lead as raw materials.

Currently, it is widely believed in the industry that the preparation process of LK-99 seems quite simple. The sample synthesis process specifically includes three steps: the first step is to uniformly mix lead oxide and lead sulfate powders in a ceramic crucible in a ratio of 50% each. The mixed powder is heated in a 725 ℃ furnace for 24 hours to undergo a chemical reaction. The second step is to mix copper and lead powder in proportion in a crucible to synthesize cuprous phosphide. The mixed powder is placed in the corresponding vacuum sealed state and then heated at 550 ℃ in the furnace for 48 hours. During this process, the mixed material undergoes a phase transition, forming cuprous phosphide crystals. Step three, grind the substances obtained from the above two steps into powder and mix them in a crucible. Then, vacuum seal the mixed powder and heat it in a 925 ℃ furnace for 5 to 20 hours.

Extracted from paper

The research team stated that during this process, the mixed powder reacts and converts into the final material, a gray black copper doped lead apatite, which is the polycrystalline material they named LK-99.

They concluded that the superconductivity of LK-99 has been demonstrated through superconducting critical temperature Tc, zero resistivity, critical current, critical magnetic field, and the Messner effect.

The research team proposed that the structure of LK-99 is very similar to that of lead apatite, but due to the phenomenon of lead being replaced by copper in the lattice, the relevant crystal cell parameters show that LK-99 has a slight shrinkage compared to the original lead apatite, with a shrinkage rate of 0.48%. The stress caused by the substitution of copper ions is transmitted to the lead in the cylindrical column, resulting in interface distortion and the formation of superconducting quantum wells.

The research team believes that it is the influence of this structure that leads to the extraordinary superconductivity of this new material, rather than external factors such as temperature and pressure. The authors of the first paper wrote that so far, the relationship between superconductivity and material structural changes has not been well elucidated. In fact, the two main factors that have been discovered to affect the superconductivity of superconductors are temperature and pressure. But both temperature and pressure can affect the volume of the material, and it seems that the stress generated by the decrease in volume at low or high temperatures can cause small strains or deformations.

The research team stated that although it is difficult to observe small structural changes in superconducting materials, these structural changes seem to bring about their superconductivity.

It is worth mentioning that the research team also uploaded a video specifically to demonstrate the suspension of LK-99 on magnets, which is known as the Meisner effect. However, the suspension of this flat, coin like material is not very perfect, and one side still seems to be in contact with a magnet. In this case, Hyun Tak Kim stated that this indicates that the sample is not perfect, with only a portion becoming superconductors and exhibiting the Meisner effect.

Although Hyun Tak Kim's current attitude reveals that the authors behind the study have different ideas, he accepts external doubts and believes that other researchers should try to replicate their team's work to address the current doubts. At the same time, Hyun Tak Kim also stated that he and other colleagues will continue to improve their current work and move towards large-scale production.

Additionally, it is worth noting that this "bullet" may not need to fly for too long. According to current theories in the field, given the simplicity of the preparation of the aforementioned new materials, there may already be a significant amount of repetitive work on the way.