superledande

Superledande, or superconductivity in English, is a quantum mechanical phenomenon in which certain materials conduct electricity with essentially zero direct current resistance when cooled below a characteristic critical temperature. In addition to vanishing resistance, superconductors exclude magnetic fields from their interior, a property known as the Meissner effect. The phenomenon is observed in a range of materials, including elemental metals, alloys, and certain ceramic compounds, with critical temperatures spanning from a few kelvin to above 100 kelvin for high-temperature superconductors. The temperature, magnetic field, and current at which superconductivity persists define the material’s critical parameters.

Most superconductors fall into two broad classes. Type I superconductors show a complete Meissner state and lose superconductivity above a relatively low critical field. Type II superconductors, which include many technologically important materials such as niobium-titanium and many cuprates, allow magnetic flux to penetrate in quantized vortices and remain superconducting up to higher fields. High-temperature superconductors, discovered in 1986, operate at temperatures above the boiling point of liquid nitrogen and have expanded potential applications.

The conventional understanding is captured by Bardeen-Cooper-Schrieffer (BCS) theory, where electrons form bound pairs (Cooper pairs) via lattice vibrations (phonons) and move without resistance. Some materials are classified as unconventional superconductors, where pairing mechanisms differ and are not fully described by BCS.

Applications include magnetic resonance imaging (MRI), particle accelerators, superconducting cables for power transmission, and maglev concepts, all benefiting from low-loss transmission and strong magnetic fields. Superconductivity is typically achieved by cryogenic cooling, using liquid helium for many elemental and alloy superconductors, or liquid nitrogen for high-temperature superconductors.