Superconductors and Superconductivity

Before Kamerlign Onnes liquefied helium in 1908 and its temperature could be lowered to about 1 K, it was known that the electric resistance of the metal decreases when cooling below room temperature. However, I do not know if the temperature drops to 0 K or not. When testing platinum it is unknown which Onnes will decrease its resistance depending on metal purity until Onnes. When the mercury temperature drops to 0 K, the resistance value decreases smoothly until the resistance drops suddenly at about 4 K.

Superconductivity is a phenomenon which occurs when the electromagnetic field appearing in some materials (called superconductors) is exactly zero and the flux field is cooled below the characteristic critical temperature. Dutch physicist Heike Kamerlingh Onnes discovered in Leiden on April 8, 1911. Like ferromagnetism and atomic beams, superconductivity is a quantum mechanical phenomenon. It is characterized by Meissner effect, ie complete emission of magnetic field lines during transition from the interior of the superconductor to the superconducting state. The appearance of Meissner effect suggests that superconductivity can not simply be understood as an idealization of complete conduction in classical physics.

To find the mechanism of superconductivity and its reason, we made a big effort; when Meisner and Okusenfeld discovered that in 1933 the superconductor bombarded the applied magnetic field, an important step took place . . In 1935, Fritz and Heinz London showed that the Meissner effect is the result of minimizing the electromagnetic free energy carried by the superconducting current. The first theory of superconductivity phenomena is the London theory. It was proposed in 1935 when Brother Fritz and Heinz London brothers discovered that magnetic fields were released by superconductors. The big victory of this theory is that when the material exceeds the superconducting threshold, the material can interpret the Meissner effect exponentially releasing all internal magnetic fields.

The superconductor means Type II, which means that it has a single critical field where superconductors are lost until the superconductor is completely discharged from the superconductor, or that it has two critical regions Type II. Allow the magnetic field to partially penetrate isolated points between these two important areas. These points are called vortices. Furthermore, in multicomponent superconductors, two behaviors can be combined. In this case, the superconductor is type 1.5.