ülijuhtimine

Ülijuhtimine refers to the phenomenon of superconductivity, a state in which certain materials exhibit zero electrical resistance when cooled below a critical temperature. This means that electric current can flow through them indefinitely without any energy loss due to heat. The discovery of superconductivity was made by Dutch physicist Heike Kamerlingh Onnes in 1911 while studying the properties of solid mercury at very low temperatures.

The underlying mechanism of superconductivity is explained by the BCS theory, named after its proponents John Bardeen, Leon Cooper, and Robert Schrieffer. This theory posits that at low temperatures, electrons in the material can form bound pairs called Cooper pairs. These pairs can then move through the material without scattering, thus leading to zero resistance.

Superconducting materials have a critical temperature (Tc), below which they become superconducting. This temperature varies significantly among different materials. For conventional superconductors, Tc values are typically very low, often requiring cooling with liquid helium. However, the discovery of high-temperature superconductors (HTS) in the late 1980s, which exhibit superconductivity at higher temperatures (though still requiring significant cooling, often with liquid nitrogen), opened up new possibilities for practical applications.

The potential applications of ülijuhtimine are vast and include highly efficient power transmission lines, powerful magnets for MRI machines and particle accelerators, magnetic levitation for high-speed trains, and sensitive detectors for various scientific instruments. Despite the promise, challenges remain in developing materials with higher critical temperatures, improving their mechanical properties, and reducing manufacturing costs for widespread adoption. Research continues to explore new superconducting materials and refine existing technologies to harness the full potential of this remarkable phenomenon.