Mapping 1D Electronic States in a 2D Quaternary Chalcogenide

Dimensionality governs how electrons interact, and one-dimensional (1D) systems can host quantum phases that differ fundamentally from those in higher dimensions. For example, 1D systems can exhibit Tomonaga–Luttinger liquid behavior and are prone to forming charge density waves. Realizing and probing these states remains challenging because truly 1D materials are often fragile and difficult to assemble into ordered structures. Anisotropic two-dimensional (2D) materials offer an alternative platform, where quasi-1D chains exhibit 1D physics within atomically precise 2D layers. Here, we use scanning tunneling microscopy and spectroscopy (STM/STS) to reveal the atomic and electronic structure of a new family of quaternary chalcogenides that naturally form such quasi-1D chains. These materials consist of four distinct chain types arranged periodically with a unique out-of-plane corrugation, directly visualized by STM. This strongly anisotropic crystal structure produces parabolic and 1D Dirac bands along the chains, with comparatively flat bands across them, signatures of which we probe using STS. Our results show the family of quaternary chalcogenides provide a versatile platform for exploring low-dimensional quantum phenomena, where metallicity and magnetism can be systematically tuned through chemical composition.