Ferroelectricity in strained <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Hf</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>CF</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math> monolayer
Ziwen Wang, Ning Ding, Churen Gui, Shan-Shan Wang, Ming An, Shuai Dong
Abstract
Low-dimensional ferroelectrics are highly desired for applications and contain exotic physics. Here a functionalized MXene ${\mathrm{Hf}}_{2}{\mathrm{CF}}_{2}$ monolayer is theoretically studied which manifests a nonpolar to polar transition upon moderate biaxial compressive strain. Accompanying this structural transition, a metal-semiconductor transition occurs. The in-plane shift of the unilateral fluorine layer leads to a polarization pointing out-of-plane. Such ferroelectricity is unconventional, similar to the recently proposed interlayer-sliding ferroelectricity but not identical. Due to its specific hexapetalous potential energy profile, the possible ferroelectric switching paths and domain walls are nontrivial, which are mediated via the metallic paraelectric state. In this sense, the metallic walls can be manipulated by reshaping the ferroelectric domains.