Local manipulation and topological phase transitions of polar skyrmions

Topological phases such as polar skyrmions have been a fertile playground for ferroelectric oxide superlattices, which demonstrate exotic physical phenomena such as negative capacitance. Herein, using phase-field simulations, we demonstrate the local control of the skyrmion phase with electric potential applied through a top electrode. Under a small bias, the skyrmions underneath the electrode can be erased and recovered reversibly. A topologically protected transition from the symmetric to asymmetric skyrmion bubble is observed near the electrode edge. While a transition to the vortex state requires a large bias, it can switch back to the skyrmion state with a relatively small opposite bias. The topological transition from +1 to 0 occurs before the destruction of the bubble structure. The shrinking and bursting of the skyrmions leads to a large reduction in the dielectric permittivity, the magnitude of which depends on the electrode size and the magnitude of the applied bias.