Supraleittavat

Supraleittavat 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 mercury at extremely low temperatures.

When a material becomes superconducting, it also develops another remarkable property called the Meissner effect. This effect describes the expulsion of magnetic fields from the interior of the superconductor. If a magnet is brought near a superconductor below its critical temperature, the superconductor will repel the magnet, causing it to levitate. This repulsion is a direct consequence of the material's ability to generate surface currents that perfectly cancel out the external magnetic field.

The critical temperature (Tc) at which a material transitions into the superconducting state varies greatly depending on the material composition. Early superconductors discovered, like mercury and lead, had very low critical temperatures, requiring cooling with liquid helium. The discovery of high-temperature superconductors (HTS) in the 1980s, which exhibit superconductivity at temperatures above the boiling point of liquid nitrogen (77 K), was a significant breakthrough, making the technology more accessible and practical for various applications. These HTS materials are typically complex ceramic oxides.

Superconductors have a wide range of potential and existing applications. They are used in powerful electromagnets for MRI machines and particle accelerators. Their zero resistance property also makes them ideal for efficient power transmission lines, high-speed magnetic levitation trains (maglev), and advanced electronic devices like superconducting quantum interference devices (SQUIDs) used in sensitive magnetic field detection. Research continues to explore new superconducting materials with higher critical temperatures and improved properties for even broader applications.