Manipulating skyrmionic polar nanodomains and creating designable conducting channels in ferroelectric thin films

Polar skyrmion nanodomains in ferroelectric materials, analogous to those in ferromagnetic systems, have attracted significant attention because of the polar states and their potential application in memories. Complex higher order topological structures such as skyrmionium and skyrmion bags found in magnetic systems possess better stability and tunability, though their counterparts are yet to be realized in ferroelectric systems. Herein, we report the observation of intricate ferroelectric domain structures in epitaxial Pb(Zr0.1Ti0.9)O3 thin films that resemble skyrmioniums with concentric skyrmions of opposing charges and skyrmion bags with additional degrees of freedom via inner skyrmions. These nanodomains result from relaxation and correlated atomic displacement in thin films and can be tuned by substrate-induced strain. Reversible transitions between three distinct topological charge states, including skyrmion (Q = 1), skyrmionium (Q = 0), and skyrmion bags (Q = 2, 4), can be controlled by external bias at room temperature. In addition, switching of topological charge states facilitates highly conducting channels with more than three orders of magnitude higher current flow than the ferroelectric matrix. Such conducting channels can also be readily configured to arbitrary patterns via scanning a biased tip. Overall, these high-density polar topological structures with superior tunability and room-temperature stability offer prospects for programmable ferroelectric devices.