Iron-Based Superconductors

Iron-based superconductors (IBS) represent a transformative class of materials that emerged in 2008, marking the second major family of high-temperature superconductors after the cuprates. Chemically, these materials are primarily composed of iron-pnictide or iron-chalcogenide layers, often interleaved with spacer layers such as rare-earth oxides or alkali metals. The fundamental structure typically features iron atoms arranged in a square lattice, coordinated by pnictogen or chalcogen atoms in a tetrahedral geometry. What makes IBS particularly compelling to the condensed matter community is their complex multiband electronic structure, where multiple charge carriers contribute to the superconducting state. This stands in contrast to the single-band behavior often associated with other systems. Furthermore, these materials exhibit high critical magnetic fields and relatively low anisotropy, which makes them highly attractive for practical engineering applications. Because they can maintain superconductivity under intense magnetic environments, they are considered prime candidates for the development of next-generation high-field magnet wires and power transmission infrastructure. Notable members of this family include the '1111' type, such as LaFeAsO, which first demonstrated the potential for high transition temperatures, and the '11' type, represented by FeSe, which is valued for its structural simplicity and unique electronic properties. As researchers continue to tune their chemical composition through doping or pressure, iron-based superconductors remain at the forefront of efforts to understand the mechanisms of unconventional superconductivity and to push the boundaries of superconducting technology in industrial settings.