Controlling polar-toroidal multi-order states in twisted ferroelectric nanowires

Abstract

The toroidal order of electric dipoles in ferroelectric materials has attracted attention in the past decade due to fascinating properties and great potential for enabling novel memory devices, and functional devices in general. However, facile manipulation of toroidal order in ferroelectrics remains challenging. Here, using first-principles derived simulations, we demonstrate an efficient scheme to control the polar-toroidal multi-order (PTMO) states in ferroelectric nanowires. Two feasible strategies of controlling PTMO states by a combination of homogeneous electric field and torque are carried out in ferroelectric/paraelectric composite nanowires. This is possible based on trilinear coupling between polarization, toroidization and the twist force. As a result, switching of the toroidization of the nanowire can be readily achieved by reversal of the axial polarization. The torque threshold needed to control PTMO states is also calculated and found to be relatively small, indicating the feasibility of this method. Our study demonstrates facile control of PTMO states, including ferroelectric skyrmions, in ferroelectrics and is a step towards designing ferroelectric devices based on multi-order states.