Title: Electric-field control of emergent phenomena in correlated oxide thin films

Place : E6-2(Natural Science B/D). 1st fl. #1323

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Transition metal oxides (TMOs) have shown intriguing physical phenomena as their structures and physical properties are strongly intertwined. Electric-field control has emerged as a novel way to tailor the lattice symmetry and associated physical phenomena of the correlated TMOs [1-3]. Here, I will present the first realization of epitaxial growth of T-Nb₂O₅ thin films, critically with vertical ionic transport channels [4]. This novel thin film form allows for a fast and colossal insulator-metal transition along with multiple hidden phase transitions, owing to the population of electrons in the initially empty Nb 4d level, via Li-ionic gating. This film further enables tunable and low voltage operation in ionic gating by chemical potential control between the gate electrode and T-Nb₂O₅ channel. In addition, by revealing time- and space-resolved electrokinetics during ionic gating, I will demonstrate a new concept of synchronized local ionic gating that allows local manipulation of electrical, magnetic, and optical properties in numerous nanostructures simultaneously [5]. This concept enables the creation and control of all-oxide metamaterials, such as active metasurfaces in addition to artificial spin ices by collective interactions between nanostructures. Finally, I will present strongly correlated SrRuO₃ thin films whose structure and physical properties can be extensively modified by external stimuli. In particular, the reversal of anomalous Hall effect coupled with octahedral tilting will be presented by the hydrogenation of SrRuO₃ thin films [6]. These studies pave a new way for electrically controlling lattice symmetry and emergent phenomena of TMOs and for their diverse potential applications.