From Bound to Topological Charges in Ferroelectric Flatlands

Ultra-thin ferroelectrics represent a paradigmatic materials platform for realizing nontrivial polar topologies. Owing to strong electrostatic interactions, the local electric dipoles in these systems are oftentimes forced to adopt swirling configurations in order maintain the right balance of bound charges both within the material and at its interfaces. As a result, one observes formation of such topological defects as electric vortex tubes and polar disclinations or skyrmion-like bubble solitons.<br/><br/>While sharing many similarities with their magnetic counterparts, these polar states have a fundamentally different, <i>electric</i>, nature which opens new opportunities to control ferroelectric topologies but also poses a question of their possible technological applications. Here, we explore these questions using effective Hamiltonian simulations of ultra-thin Pb(Zr,Ti)O₃ films under residual depolarizing fields. On the one hand, our results reveal how the screening and local electric fields can be tuned to induce topological transitions and control the dynamical behavior of polar topological defects and solitons. On the other hand, we inquire into the role of bound electric charges intrinsically associated with polar disclinations and bubbles. Namely, we explore the effect of such charges on interactions between electric topological defects and discuss possible implications of such charge on functional properties of polar topologies.<br/><br/>Research supported by the Vannevar Bush Faculty Fellowship Grant No. N00014-20-1-2834 from the Department of Defense.