Two-Dimensional Triferroics: From Fundamental Couplings to Multifunctional Applications.

Triferroic compounds, characterized by the coexistence and coupling of more than two ferroic orders, have attracted considerable attention as a novel class of multiferroic materials. Compared with conventional multiferroics dominated by pairwise coupling, the involvement of a third ferroic order enables more complex and tunable functional responses, facilitating deterministic multistate control. Although triferroicity has so far been observed only in 3D systems, extending it to 2D materials is particularly appealing, as 2D systems offer advantages such as high storage density, low energy consumption, and mechanical flexibility. In this review, we provide a comprehensive overview of recent progress in 2D triferroic materials, with a particular focus on the origin and interplay of the three ferroic orders at the structural and electronic levels. In addition, we highlight potential applications of 2D triferroics, including multistate storage and spintronic devices. Finally, we outline several promising directions for future research and development in the field of 2D triferroics.