Frustrated Dipole Order Induces Noncollinear Proper Ferrielectricity in Two Dimensions

Phys Rev Lett. 2019 Aug 9;123(6):067601. doi: 10.1103/PhysRevLett.123.067601.

Abstract

Within Landau theory, magnetism and polarity are homotopic, displaying a one-to-one correspondence between most physical characteristics. However, despite widely reported noncollinear magnetism, spontaneous noncollinear electric dipole order as a ground state is rare. Here, a dioxydihalides family is predicted to display noncollinear ferrielectricity, induced by competing ferroelectric and antiferroelectric soft modes. This intrinsic of dipoles generates unique physical properties, such as Z_{2}×Z_{2} topological domains, atomic-scale dipole vortices, and negative piezoelectricity.