Miracle at Low Temperature - Superconductivity

In 1911, Camolin Ennis of Leiden University in the Netherlands unexpectedly discovered the phenomenon of mercury's resistance disappearing at -268.98 ° C; Later, many metals and alloys were discovered to have the characteristic of losing resistance at low temperatures similar to mercury. Due to its special conductivity, Camolin Onnis referred to them as superconducting states. Camolin won the Nobel Prize in 1913 for his discovery.

This discovery caused a worldwide shock. After him, people began to refer to conductors in a superconducting state as' superconductors'. The sudden disappearance of the DC resistivity of superconductors at a certain low temperature is known as the zero resistance effect. Without resistance in a conductor, there is no heat loss when the current flows through the conductor. The current can flow large amounts of current in the conductor without resistance, resulting in a super strong magnetic field.

In 1933, Messner and Orsenfeld of the Netherlands jointly discovered another extremely important property of superconductors. When a metal is in a superconducting state, the magnetic induction inside the superconductor is zero, but the magnetic field that originally existed inside the body is squeezed out. Experiments on single crystal tin balls have found that when the tin ball transitions to a superconducting state, the magnetic field around the tin ball suddenly changes, and the magnetic field lines seem to be suddenly pushed out of the superconductor. This phenomenon is known as the "Meissner effect".

Later, people also conducted such an experiment: in a shallow flat tin plate, a small but strong permanent magnet was placed, and the temperature was lowered to make the tin plate appear superconducting. At this time, it can be seen that the small magnet left the surface of the tin plate and slowly floated up, suspended in the air. The Meisner effect is of great significance as it can be used to determine whether substances have superconducting properties.

In order to make superconducting materials practical, people began to explore the process of high-temperature superconductivity. From 1911 to 1986, the superconducting temperature increased from 4.2K of mercury to 23.22K (OK=-273 ° C). In January 1986, it was discovered that the superconducting temperature of barium lanthanum copper oxide was 30K. On December 30th, this record was set at 40.2K. In January 1987, it rose to 43K, and soon rose to 46K and 53K. On February 15th, 98K superconductors were discovered, and signs of superconductivity were soon discovered at 14 ° C. High temperature superconductors made a huge breakthrough, leading to large-scale application of superconducting technology.

Superconducting materials and superconducting technology have broad application prospects. The Meissner effect in superconductivity allows people to use this principle to manufacture superconducting trains and ships. As these vehicles will operate in a frictionless state, this will greatly improve their speed and quiet performance. Superconducting trains have successfully conducted manned feasibility tests in the 1970s. Since 1987, Japan has started trial operation, but failures often occur, which may be caused by bumps caused by high-speed driving. The superconducting ship was launched for sea trial on January 27, 1992, and has not yet entered the practical stage. There are still certain technological obstacles to using superconducting materials to manufacture transportation vehicles, but it is bound to trigger a wave of transportation revolution.

The zero resistance characteristic of superconducting materials can be used for power transmission and the manufacturing of large magnets. Ultra high voltage transmission can have significant losses, and the use of superconductors can minimize losses. However, due to the fact that superconductors with higher critical temperatures have not yet entered the practical stage, the use of superconducting transmission is limited. With the development of technology and the continuous emergence of new superconducting materials, the hope of superconducting power transmission will soon come true.

The existing high-temperature superconductors are still in a state where liquid nitrogen must be used for cooling, but they are still considered one of the greatest discoveries of the 20th century.