Electric field Controllable “Negative Capacitance” in Polar Skyrmions: Topological transition?*

Complex topological configurations are a fertile arena to explore novel emergent phenomena and exotic phases in condensed-matter physics. For example, the recent discovery of polar skyrmions, vortices in superlattices of (PbTiO₃)_n/(SrTiO₃)_nsuggests the presence of a complex, multi-dimensional system capable of exotic physical responses. Here, we demonstrate electric field controlled room-temperature negative capacitance and topological phase transition in polar skyrmions. In epitaxially grown heterostructures of PbTiO₃ and SrTiO₃capacitance was found to be larger compared to its indivual constituent's capacitance SrTiO₃, PbTiO₃. This indicates the indicates the ferroelectric was stabilized in a state of negative capacitance at room temperature. This phenomenon could be controlled by electric field and temperature. The STEM measurement, Phase field and Second principle calculation confirms the stable negative capacitance is due to boundary of polar skyrmions.Such phenomena could advance ferroelectrics towards new levels of functionality.
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