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Breaking through the limit, China leads the world in high temperature superconductivity research

via:博客园     time:2019/10/14 10:02:37     readed:92

Chinese Journal of Science and Technology, Wu Changfeng

Just in the golden week of the National Day, the Chinese Academy of Science and Technology's superconducting research team is still working in the lab every day, in addition to watching the 70th anniversary of the National Day.

to break through the exclusion zone of the superconducting study

Superconductivity refers to the phenomenon that the resistance of some materials suddenly disappears when the temperature drops to a critical temperature or below the superconducting transition temperature. In the history of superconducting research, 10 people have won five Nobel Prizes, and its scientific importance is self-evident.

In 1911, Dutch scientists discovered the superconductivity of mercury at extremely low temperatures, opening up a new field of scientific research. In 1986, German and Swiss scientists discovered a copper oxide superconductor with a critical transition temperature of 35K.

What bothers scientists is that the transition temperature of superconductors cannot exceed 40K (about minus 233 degrees Celsius), also known as the McMillan limit temperature.

Can the limit temperature of 40K be broken through? Shortly after two European scientists discovered copper oxide superconductors with copper as the key superconducting element, research teams, including Chinese scientists, raised the critical transition temperature of copper oxide superconductors above liquid nitrogen temperature, breaking through the McMillan limit temperature and making them high temperature superconductors.

Because of its magnetic factors, iron-based compounds have been almost affirmed by the international physics circles as a restricted area for exploring high temperature superconductors.

In March 2008, the superconducting transition temperatures of 43K and 41K were simultaneously observed in the iron base by Chen Xianhui and Wang Nanlin of the Institute of Physics of the Chinese Academy of Sciences, breaking through the McMillan limit and proving that iron-based superconductors are high temperature superconductors. Then, the Chinese team of scientists not only took the lead in breaking the transition temperature beyond 50K, but also found a series of superconductors above 50K, and also created a 55K record of the transition temperature of iron-based superconductors, which is recognized as the second high temperature superconductor family by the international physics community.

Looking for Superconducting Materials with Higher Transition Temperature

After breaking through the McMillan limit, scientists all over the world are confused about the exploration of superconducting materials again. Publishing high temperature superconducting papers in journals with high impact factors becomes more and more difficult.

The middle-and-large superconducting team has been holding the position, making, observing, giving up, and restarting.

Wu Tao told reporters that because copper-oxygen and iron-based superconductors are layered, the key structural units carrying superconductivity are the CuO2 surface and the FeAs/Se layer, which are called the copper-oxygen and iron-based superconductors.

At present, there are two key points in the research of superconductivity: the first is the new (high transition temperature) unconventional superconducting materials, and the second is the mechanism of high temperature superconducting (and unconventional superconducting).

Exploring superconductors that are more suitable for application

In fact, superconductors have begun to enter our lives. For example, HTS filter has been used in mobile phone and satellite communication, and obviously improves the communication quality; superconducting quantum interference device (SQUID) is used in medical equipment, which greatly strengthens the accuracy and sensitivity of heart and brain detection and inspection of human body; the first superconducting demonstration substation in the world has also been put into use in the power grid of our country.

In the view of Wu Tao, their research will play an important role in the field of superconducting quantum computing for the key development of the country.

At present, the superconductor has not reached the desired wide application, the main reason is that there are two important problems to be solved: first, the economy of the superconducting application; the other is that the superconducting material at normal temperature and normal pressure is still not found.

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