Superconductivity in compressed quasi−one-dimensional face-sharing hexagonal perovskite chalcogenides

Oxide perovskite superconductors typically feature stacks of metal-oxygen octahedra or planar blocks connected through corners, forming three-dimensional (3D) or 2D layered structures. Here, we find a group of quasi-1D superconducting materials among hexagonal perovskite chalcogenides with face-sharing connectivity. Resistance and magnetization measurements demonstrate anisotropic superconductivity in compressed barium titanium trisulfide (BaTiS₃) at a low hole carrier concentration of (1.6 ± 0.1) × 10²¹ per cubic centimeter, with the highest superconducting temperature (T_c) reaching ~9.3 kelvin. Synchrotron x-ray diffraction indicates that the superconducting phase retains a hexagonal perovskite structure consisting of quasi-1D infinite titanium hexasulfide chains. Density functional theory calculations, combined with the observed decrease in the maximum T_c from ~9.3 to ~6.2 kelvin upon substituting sulfur with selenium, suggest that electron-phonon interactions play a key role in the pairing mechanism of superconducting BaTiX₃ (X = sulfur and selenium). Our study offers a quasi-1D platform with face-sharing metal-chalcogen octahedra for understanding the mechanism of emerging electronic states in perovskite materials.