supralevytetyistä

Supralevytetyistä, also known as superconductors, are materials that exhibit zero electrical resistance and the Meissner effect, which is the expulsion of magnetic fields from their interior. This phenomenon occurs below a certain critical temperature, known as the superconducting transition temperature (Tc). The first superconducting material discovered was mercury at 4.2 Kelvin in 1911. Since then, numerous materials have been identified as superconductors, including metals, ceramics, and more recently, iron-based compounds.

Superconductors are classified into two main types: Type I and Type II. Type I superconductors, such as aluminum and lead, exhibit a sharp transition to the superconducting state and completely expel magnetic fields. Type II superconductors, like high-temperature superconductors (HTS) such as yttrium barium copper oxide (YBCO), allow magnetic fields to penetrate in the form of quantized vortices.

The mechanism of superconductivity is still an active area of research. The most widely accepted theory is the Bardeen-Cooper-Schrieffer (BCS) theory, which describes superconductivity as a result of electron pairing due to lattice vibrations. However, this theory does not fully explain the behavior of high-temperature superconductors. Other theories, such as the Hubbard model and the resonating valence bond theory, have been proposed to account for the behavior of these materials.

Applications of superconductors include magnetic resonance imaging (MRI), magnetic levitation (maglev) trains, and high-field magnets for particle accelerators. However, the high cost and low critical temperatures of many superconductors limit their widespread use. Ongoing research aims to develop new superconducting materials with higher critical temperatures and more practical applications.