FeSe

Iron selenide (FeSe) is an inorganic compound composed of iron and selenium atoms in a 1:1 stoichiometric ratio. It crystallizes in a tetragonal structure similar to that of iron sulfide (FeS), with iron atoms occupying the center of selenium tetrahedra. The compound exhibits metallic conductivity and has garnered significant scientific interest due to its superconducting properties.

FeSe has a relatively simple crystal structure belonging to the PbO-type structure family, with lattice parameters of approximately 3.77 Å for the a-axis and 5.52 Å for the c-axis at room temperature. The material undergoes a structural phase transition from tetragonal to orthorhombic symmetry at around 90 Kelvin under ambient pressure conditions.

The superconducting transition temperature of FeSe is approximately 8 Kelvin at ambient pressure, which can be enhanced to over 37 Kelvin under applied pressure of about 1.2 gigapascals. This pressure-induced enhancement makes FeSe one of the simplest iron-based superconductors studied extensively in condensed matter physics research.

FeSe thin films grown on strontium titanate (SrTiO3) substrates have shown remarkable superconducting properties, with critical temperatures exceeding 65 Kelvin. This interface-enhanced superconductivity has attracted considerable attention for potential applications in quantum computing and other low-temperature electronic devices.

The compound can be synthesized through various methods, including solid-state reactions between iron and selenium powders at elevated temperatures, chemical vapor transport techniques, and molecular beam epitaxy for thin film preparation. FeSe is sensitive to air and moisture, requiring careful handling and storage under inert atmosphere conditions.

Research on FeSe continues to advance understanding of iron-based superconductivity mechanisms and quantum materials physics, with ongoing investigations into its electronic structure, magnetic properties, and potential device applications.