  Room-temperature polar skyrmion bubbles that are recently found in oxide
superlattice, have received enormous interests for their potential applications
in nanoelectronics due to the nanometer size, emergent chirality, and negative
capacitance. For practical applications, the ability to controllably manipulate
them by using external stimuli is prerequisite. Here, we study the dynamics of
individual polar skyrmion bubbles at the nanoscale by using in situ biasing in
a scanning transmission electron microscope. The reversible electric
field-driven phase transition between topological and trivial polar states are
demonstrated. We create, erase and monitor the shrinkage and expansion of
individual polar skyrmions. We find that their transition behaviors are
substantially different from that of magnetic analogue. The underlying
mechanism is discussed by combing with the phase-field simulations. The
controllable manipulation of nanoscale polar skyrmions allows us to tune the
dielectric permittivity at atomic scale and detailed knowledge of their phase
transition behaviors provides fundamentals for their applications in
nanoelectronics.
