superkonduktoripohjaiset

Superconductors are materials that, below a characteristic critical temperature (Tc), exhibit zero electrical resistance and expel magnetic fields (the Meissner effect). This combination enables lossless current flow and the creation of strong, stable magnetic fields, distinguishing superconductivity from ordinary conductive behavior at low temperatures.

Discovered in 1911 by Heike Kamerlingh Onnes in mercury, superconductivity led to the distinction between Type I and Type II materials. The BCS theory, developed in 1957 by Bardeen, Cooper, and Schrieffer, explains conventional superconductivity as the formation of Cooper pairs of electrons bound by lattice vibrations (phonons).

Conventional superconductors are typically elemental or simple compounds, with low Tc requiring cooling near absolute zero. In 1986, high-temperature superconductors based on copper oxides (cuprates) shattered expectations with Tc well above the boiling point of liquid nitrogen, followed by the discovery of iron-based superconductors. Some materials exhibit superconductivity only under very high pressures, and hydrogen-rich compounds have shown near-room-temperature Tc under extreme pressures, demonstrating potential but limiting practicality of current breakthroughs.

Applications include magnetic resonance imaging (MRI), particle accelerators and magnetic confinement in fusion experiments, maglev transport, and superconducting qubits used in certain quantum computers. Advances in superconducting power cables and fault-current limiters aim to reduce energy losses in grids, but widespread deployment is hindered by cooling needs and material performance at practical temperatures and fields.

Key material properties are Tc, the upper critical field Hc2, and the critical current density Jc. Research continues to discover new superconductors, understand unconventional mechanisms, and push toward higher operating temperatures and more practical cooling requirements.