Supraleitavaksi

Supraleitavaksi, also known as superconductivity, is a phenomenon occurring in certain materials where electrical resistance vanishes. Discovered in 1911 by Dutch physicist Heike Kamerlingh Onnes, superconductivity is characterized by the Meissner effect, the complete ejection of magnetic flux fields from the interior of the superconductor as it transitions into the superconducting state. The critical temperature, above which the material loses its superconducting properties, varies depending on the material. Below this critical temperature, an electric current can flow indefinitely without any loss of energy.

Superconductors are classified into two main categories: Type I and Type II. Type I superconductors, such as mercury and lead, exhibit a sharp transition to the superconducting state and completely expel magnetic fields. Type II superconductors, like niobium-titanium and yttrium barium copper oxide (YBCO), allow a certain amount of magnetic flux to penetrate, forming quantized vortices. These vortices can move without dissipating energy, allowing for the existence of a critical current.

The mechanism behind superconductivity is still not fully understood, but it is generally believed to involve the pairing of electrons into Cooper pairs, which can move through the material without resistance. This pairing is thought to be mediated by phonons, the quantized vibrations of the crystal lattice.

Applications of superconductivity include magnetic resonance imaging (MRI), particle accelerators, and high-speed maglev trains. However, the practical use of superconductors is limited by the need for extremely low temperatures, typically achieved using liquid helium. Research is ongoing to develop high-temperature superconductors that can operate at more accessible temperatures.