New type superconductor magnesium diboride (MgB2)
Discovery, properties, mechanism and application prospect of magnesium diboride
At the beginning of March 2001, Japanese scientists reported that the binary material magnesium diboride showed superconductivity at about 39 K. This discovery quickly aroused a worldwide research upsurge. The research progress on the properties of magnesium diboride superconductors is very rapid, and the understanding of the mechanism of magnesium diboride superconductors is also deepening. Theoretical calculation shows that there is more than one energy band across the Fermi plane in magnesium diboride, and the instability of the Fermi plane caused by electro-acoustic coupling may completely generate energy gap at the Fermi plane of the two energy bands, which is very different between magnesium diboride superconductors and traditional superconductors. The images of the two energy gaps were later widely confirmed by experiments of specific heat, nuclear magnetic resonance, electron tunneling spectroscopy and angular resolved photoelectron spectroscopy. At present, how the two energy gaps are formed and how they affect the superconductivity are the focus of research on magnesium diboride superconductors.
The application of magnesium diboride superconductors is even more exciting. First of all, at a temperature of about 20 K, the superconductor can carry a large superconducting current at a magnetic field of 80000 times that of the earth, and its energy consumption is extremely low. Secondly, the price of magnesium diboride material is very low, and it is far easier to be processed than the oxide high-temperature superconductor with ceramic characteristics. In addition, magnesium diboride superconductor has a long superconducting coherence length, which makes it easy to prepare superconducting quantum interference devices for detecting weak electromagnetic signals. It has a broad application prospect in geological prospecting, medical instruments, environment and military.
Chinese scientists have also carried out research work on magnesium diboride superconductors: the research team of Ma Yanwei, a researcher at the Key Laboratory of Applied Superconductivity of the Institute of Electrical Engineering of the Chinese Academy of Sciences, the research team of Wen Haihu, a researcher at the Institute of Physics of the Chinese Academy of Sciences, and Professor K Watanabe, of Northeastern University of Japan, have made a series of new progress in the preparation and performance research of new superconducting material magnesium diboride (MgB2) wire and strip.
The concept of superconductor and the process of people looking for superconductors: superconductors, as the name implies, are conductors without energy dissipation after current is applied. It is the result that a large number of paired electrons are condensed into a coherent state with "consistent steps", and their motion is not subject to lattice scattering. After the Dutch scientist Onas discovered the superconductivity of mercury in 1911, people have been looking forward to finding room temperature superconductors. At the end of 1986, Bernoz and Miller of Switzerland first found superconductors with a transition temperature of more than 30 K in previously unexpected oxides, setting off a chase for high-temperature superconductivity in the world. At present, the transition temperature of oxide superconductors has reached more than 130 K, and their applications in some areas have emerged. However, due to its own characteristics, the application of oxide superconductors in many aspects is limited.