Strong Dzyaloshinskii-Moriya Interaction and Origin of Ferroelectricity inCu2OSeO3

Abstract

By performing density functional calculations, we investigate the origin of the Skyrmion state and ferroelectricity in ${\mathrm{Cu}}_2{\mathrm{OSeO}}_3$. We find that the Dzyaloshinskii-Moriya interactions between the two different kinds of Cu ions are extremely strong and induce the helical ground state and the Skyrmion state in the absence and presence of a magnetic field, respectively. On the basis of the general model for the spin-order induced polarization, we propose that the ferroelectric polarization of ${\mathrm{Cu}}_2{\mathrm{OSeO}}_3$ in the collinear ferrimagnetic state arises from an unusual mechanism, i.e., the single-spin-site contribution due to the spin-orbit coupling.