Atomic-Scale Origin of the Quasi-One-Dimensional Metallic Conductivity in Strontium Niobates with Perovskite-Related Layered Structures.

The quasi-one-dimensional (1D) metallic conductivity of the perovskite-related SrNbO compounds is of continuing fundamental physical interest as well as being important for developing advanced electronic devices. The SrNbO compounds can be derived by introducing additional oxygen into the SrNbO perovskite. However, the physical origin for the transition of electrical properties from the three-dimensional (3D) isotropic conductivity in SrNbO to the quasi-1D metallic conductivity in SrNbO requires more in-depth clarification. Here we combine advanced transmission electron microscopy with atomistic first-principles calculations to unambiguously determine the atomic and electronic structures of the SrNbO compounds and reveal the underlying mechanism for their quasi-1D metallic conductivity. We demonstrate that the local electrical conductivity in the SrNbO compounds directly depends on the configuration of the NbO octahedra in local regions. These findings will shed light on the realization of two-dimensional (2D) electrical conductivity from a bulk material, namely by segmenting a 3D conductor into a stack of 2D conducting thin layers.