szupravezetés

Superconductivity is a phenomenon observed in certain materials when they are cooled below a critical temperature. In this state, the material exhibits two main properties: zero electrical resistance and the expulsion of magnetic fields. Zero electrical resistance means that electric current can flow through the superconductor indefinitely without any energy loss due to heat. This is a stark contrast to normal conductors, which always have some resistance. The expulsion of magnetic fields is known as the Meissner effect. When a superconductor is cooled below its critical temperature in the presence of a magnetic field, it will actively expel the magnetic field lines from its interior.

The discovery of superconductivity dates back to 1911 when Heike Kamerlingh Onnes observed that mercury lost all electrical resistance at approximately 4.2 Kelvin. Since then, many other elements and alloys have been found to be superconducting, with critical temperatures varying widely. The theoretical explanation for superconductivity in conventional materials is provided by the Bardeen-Cooper-Schrieffer (BCS) theory, which describes how electrons can form bound pairs (Cooper pairs) that move through the material without scattering.

In recent decades, high-temperature superconductors have been discovered, materials that exhibit superconductivity at much higher temperatures, although still well below room temperature. These materials, often complex ceramic oxides, have opened up new possibilities for technological applications. Potential applications of superconductivity include highly efficient power transmission lines, powerful electromagnets for medical imaging (MRI) and particle accelerators, magnetic levitation trains, and advanced computing. However, the requirement of extremely low temperatures for most superconductors remains a significant challenge for widespread commercial adoption.