Supraleittava

Supraleittava is Finnish for superconducting or superconductivity. In physics, superconductivity is a quantum phenomenon in which a material conducts electricity with zero direct-current resistance and often expels magnetic fields when cooled below a characteristic critical temperature. The term is widely used in Finnish-language texts to describe materials, devices, and effects related to this phenomenon.

Key properties of supraleittava materials include zero electrical resistance at and below the critical temperature (Tc), the Meissner–Oersted effect (expulsion of magnetic fields), and a critical current density that marks the limit of the superconducting state. Many superconductors also have a critical magnetic field, beyond which superconductivity is destroyed. Superconductors are commonly categorized as type I or type II, with type II materials sustaining superconductivity in higher magnetic fields by allowing magnetic vortices.

Mechanisms and classes: Conventional, or low-temperature, superconductors are explained by BCS theory, which describes Cooper pairing of electrons mediated by lattice vibrations (phonons). High-temperature superconductors, discovered in 1986, are largely copper-oxide ceramics and do not fit neatly into BCS theory, leading to ongoing research into their pairing mechanisms. In recent years, hydrogen-rich compounds under high pressures have demonstrated superconductivity at comparatively high temperatures, though under extreme conditions.

Materials: Early examples include elemental mercury, which Onnes showed would superconduct at 4.2 K. Modern applications use niobium-titanium (NbTi) and Nb3Sn for superconducting magnets, copper-oxide superconductors such as YBCO, and iron-based superconductors. Record high critical temperatures have been achieved in hydride superconductors under high pressures.

Applications and impact: Supraleittavat materials enable MRI machines, magnetic levitation transport, and superconducting magnets for particle accelerators and fusion devices. They hold potential for lossless power transmission and advanced energy storage, subject to materials and engineering challenges.

See also: superconductivity, high-temperature superconductivity.