title: Spin-orbital driven ferroelectricity.
abstract: We study the effect of octahedron rotation on the electric polarization with spin-orbit coupling. Employing local coordinates to represent the tilting of the ligands' octahedra, we evaluate the electric polarization in a chain of transition metal ions with non-polar octahedron rotation. We find the orbital ordering produced by the ligands' rotation and the spin order, together, determine the polarization features, manifesting that non-vanishing polarization appears in collinear spin order and the direction of polarization is no more restricted in the plane of spin rotation in cycloidal ordering.
authors.affiliation: Zhejiang Institute of Modern Physics and Department of Physics, Zhejiang University, Hangzhou 310027, People's Republic of China.
authors.forename: Shan
authors.initials: S
authors.lastname: Zhu
authors.forename: You-Quan
authors.initials: YQ
authors.lastname: Li