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 Sr n Nb n O 3 n +2 compounds is of continuing fundamental physical interest as well as being important for developing advanced electronic devices. The Sr n Nb n O 3 n +2 compounds can be derived by introducing additional oxygen into the SrNbO 3 perovskite. However, the physical origin for the transition of electrical properties from the three-dimensional (3D) isotropic conductivity in SrNbO 3 to the quasi-1D metallic conductivity in Sr n Nb n O 3 n +2 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 Sr n Nb n O 3 n +2 compounds and reveal the underlying mechanism for their quasi-1D metallic conductivity. We demonstrate that the local electrical conductivity in the Sr n Nb n O 3 n +2 compounds directly depends on the configuration of the NbO 6 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.