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Curvature conservation is a common feature for the physical properties with topological constraints, from the macroscopic cosmic string loops to the microscopic quantized vortex rings in the superfluid. Interestingly, ferroelectric domain-wall curvature is important to determine its conduction, which is the key parameter for designing domain-wall nanoelectronic devices. Here, we demonstrate the curvature conservation of the charged domain walls confined in ferroelectric topological structures with specific domain symmetry by combining piezoelectric force microscopy, conducting atomic force microscopy, and phase-field simulations. Significantly, the intrinsic conductivity of the charged domain walls exhibits an inverse functional relationship with the local domain-wall curvature in the ferroelectric BiFeO 3 nano-islands, which can also be precisely and continuously modulated by applying an electric field. This work provides us with an insightful understanding of the conduction mechanism of charged domain walls confined in ferroelectric topological structures with a high degree of spatial symmetry, which paves the way for the application of charged domain walls as flexible conducting channels with continuously changing resistance states to be used for ferroelectric domain-wall memristors. [Display omitted] [ABSTRACT FROM AUTHOR]

Ferroelectric tunnel junctions have attracted intensive research interest due to the fundamental physics and potential applications in high-density data storage and neuromorphic computation. However, the intrinsic physical origin, especially at atomic scale, of polarization-controllable tunneling current is still controversial due to the degradation of ferroelectric polarization and the extrinsic conduction induced by defects or oxygen vacancies. Here, a large tunneling electroresistance effect of over 10,000% in a thick (∼15 nm) tetragonal-phase BiFeO 3 thin film is observed, where a nanoscale point-contact geometry is delicately designed to reduce the extrinsic defect effects. By combining transmission electron microscopy and first-principles calculations, the atomic and electronic structures of BiFeO 3 tunneling layer are investigated. The corresponding results indicate the different charge transfer occurs at the top and bottom interface, which induces distinct tunneling barrier asymmetry when the polarization direction is opposite. Graphical abstract [Display omitted]. [ABSTRACT FROM AUTHOR]