TaSe2

TaSe2, or tantalum diselenide, is a transition metal dichalcogenide (TMDC) with the chemical formula TaSe2. It forms layered crystals in which sheets of tantalum are sandwiched between two sheets of selenium. The layers are held together by van der Waals forces, enabling exfoliation to thin flakes or monolayers. TaSe2 exists in several polymorphs, most notably the 2H (hexagonal) and 1T (tetragonal) structures. In 2H-TaSe2, tantalum atoms occupy a trigonal prismatic coordination within each layer; in 1T-TaSe2 they reside in an octahedral coordination. The different stacking and coordination lead to distinct electronic properties.

Electronic properties of TaSe2 are characteristic of many TMDCs: it is metallic and can host complex electronic ordering phenomena. The material exhibits charge density wave (CDW) behavior in several polymorphs, with transitions that depend on temperature and structural form. The CDW states can be incommensurate or commensurate and may interact with superconductivity in some samples or under specific conditions. Superconductivity has been reported in doped or intercalated forms and under applied pressure, typically at temperatures well below room temperature.

Preparation and forms of TaSe2 include solid-state synthesis from tantalum and selenium precursors or chemical vapor transport for crystal growth. Bulk material can be mechanically or chemically exfoliated to generate thin layers, enabling studies of two-dimensional physics and the integration of TaSe2 into thin-film devices.

TaSe2 is of interest as a model TMDC for investigating the interplay between low-dimensional electron systems, CDW order, and superconductivity. It is widely studied in fundamental research on phase transitions, electron-phonon coupling, and the potential for future nanoelectronic and optoelectronic applications.