Suprajäähtyminen

Suprajäähtyminen, also known as superconductivity, is a phenomenon observed in certain materials when cooled below a critical temperature. In this state, the material exhibits zero electrical resistance, meaning that electric current can flow through it indefinitely without any energy loss. This is a remarkable departure from the behavior of normal conductors, which always have some resistance and generate heat when current passes through them.

Beyond zero resistance, superconductors also possess another defining characteristic: the Meissner effect. When a superconductor is cooled below its critical temperature in the presence of an external magnetic field, it expels the magnetic field lines from its interior. This expulsion is perfect and complete, making the superconductor act as a perfect diamagnet. If a magnet is placed above a superconductor, the expelled magnetic field can levitate the magnet, a visually striking demonstration of the Meissner effect.

The phenomenon of superconductivity was first discovered in 1911 by Heike Kamerlingh Onnes. Since then, extensive research has led to the discovery of numerous superconducting materials, categorized broadly into Type I and Type II superconductors. Type I superconductors exhibit a sharp transition to the superconducting state and completely expel magnetic fields up to a critical field strength. Type II superconductors, on the other hand, have a more complex response to magnetic fields, allowing partial penetration in a mixed state before losing superconductivity entirely at a higher critical field.

Applications of superconductivity are vast and continue to expand. They are crucial in powerful electromagnets used in MRI scanners, particle accelerators, and magnetic levitation (maglev) trains. The development of high-temperature superconductors has further broadened the possibilities for energy-efficient technologies, including lossless power transmission lines and advanced computing.