The Wonders of the Cryogenic World: Superconductivity and Its Application Prospects

At room temperature, electric current flowing through metallic conductors encounters resistance, resulting in energy dissipation in the form of heat. However, in 1911, scientists discovered that when mercury is cooled to approximately 4.2 Kelvin (around -269°C), its electrical resistance abruptly drops to zero! This physical phenomenon is termed "superconductivity". Simultaneously, superconductors exhibit "perfect diamagnetism" – the Meissner effect – repelling external magnetic fields to achieve zero magnetic flux density within.
Zero resistance enables virtually lossless electricity transmission, a revolutionary advancement. Superconducting coils can form superconducting magnets far surpassing conventional electromagnets in strength, while requiring minimal energy to maintain operation. Currently, the most mature applications of superconducting technology include:
Medical imaging: Hospital MRI scanners rely on powerful superconducting magnets to generate stable, uniform magnetic fields that detect hydrogen signals within the human body.
Scientific experiments: Large particle colliders (such as CERN's Large Hadron Collider) require superconducting magnets spanning several kilometres to confine and accelerate particles.
Maglev transport: The intense magnetic fields of superconducting magnets enable train levitation and guidance, exemplified by Japan's experimental superconducting maglev train line.
Currently, the greatest challenge in superconducting applications lies in the extremely low temperatures required (typically maintained using costly liquid helium). Consequently, the global scientific community is intensely pursuing the discovery of "high-temperature superconducting materials" capable of achieving superconductivity at higher temperatures, such as within the liquid nitrogen temperature range (-196°C). Should a breakthrough be achieved, superconducting technology holds immense potential for expansion into further domains including power grids, new energy sources, and quantum computing.