Szupervezet

Szupervezető (Hungarian for superconductor) refers to a material that shows zero electrical resistance and the expulsion of magnetic fields below a characteristic critical temperature. This state, marked by the Meissner effect, allows currents to circulate without energy loss under suitable conditions. Superconductivity disappears when the temperature rises above the critical temperature or when exposed to magnetic fields stronger than a material’s critical field.

Conventional superconductors are explained by BCS theory, in which electrons form Cooper pairs via lattice vibrations (phonons) and move without scattering. There are two broad classes: Type I superconductors, which completely expel magnetic fields up to a single critical field, and Type II superconductors, which enter a mixed state with vortices between lower and upper critical fields (Hc1 and Hc2).

High-temperature superconductors, including cuprates discovered in 1986 by Bednorz and Müller, have Tc above the boiling point of liquid nitrogen (77 K), enabling easier cooling. Other families include iron-based superconductors. The mechanism of many high-Tc materials remains a topic of active research and is not fully captured by conventional BCS theory.

Applications span powerful magnets for magnetic resonance imaging (MRI) and particle accelerators, maglev transport, and potential low-loss power transmission. Superconducting circuits underpin many quantum computing platforms, with superconducting qubits such as transmons and flux qubits widely studied.

Research continues toward room-temperature superconductivity at ambient pressure. Some hydride compounds under extreme pressures have exhibited Tc above 250 K, but the required pressures are prohibitive for practical use. The search for new materials and a complete understanding of unconventional pairing remain central goals.