Surface Ferron Excitations in Ferroelectrics and Their Directional Routing

Abstract: The duality between the electric and magnetic dipoles inspires recent comparisons between ferronics and magnonics. Here we predict surface polarization waves or ferrons" in ferroelectric insulators, taking the long-range dipolar interaction into account. We predict properties that are strikingly different from the magnetic counterpart, \textit{i.e.} the surfaceDamon-Eshbach" magnons in ferromagnets. The dipolar interaction pushes the ferron branch with locked circular polarization and momentum to the ionic plasma frequency. The low-frequency modes are on the other hand in-plane polarized normal to their wave vectors. The strong anisotropy of the lower branch renders directional emissions of electric polarization and chiral near fields when activated by a focused laser beam, allowing optical routing in ferroelectric devices.