(TaSe₄)₂I (Tantalum Selenide Iodide)

A quasi-one-dimensional van der Waals compound, space group I422, consisting of TaSe₄ chains running along the c-axis that are weakly linked by iodine. The chains host a well-defined charge density wave (CDW) below ~263 K, and (TaSe₄)₂I is regarded as a candidate axion insulator, in which a sliding CDW couples to the electromagnetic response to produce an axionic contribution; a giant current-driven CDW sliding and anomalous transport have been reported, making it a central platform for studying topological CDW physics and axion electrodynamics.