Hourglass Nodal Ring in the Monolayer Material NaSH.

The landscape of topological materials research has witnessed a remarkable expansion in recent years, with 2D systems emerging as a vibrant frontier. Our computational study unveils an extraordinary topological state within the monolayer ternary compound NaSH, characterized by an exceptional hourglass nodal ring. Through rigorous symmetry analysis and model calculations, we elucidate the intricate formation mechanism underlying this nodal ring and its distinctive hourglass dispersion. The configuration stands out for its remarkable simplicitymanifesting exclusively through four bands, representing arguably one of the simplest realizations of hourglass-type band crossing observed to date. The associated edge states demonstrate remarkable spatial separation from bulk electronic projections, a feature that significantly enhances the prospects for experimental verification. The material's lightweight elemental composition confers an additional remarkable attribute: both the hourglass dispersion and corresponding edge states maintain their structural integrity even under spin-orbit coupling effects. This robustness positions the NaSH monolayer as a particularly promising platform for investigating fundamental topological phenomena. To substantiate the material's technological potential, we conducted comprehensive mechanical characterizations, revealing anisotropic behaviors across different crystallographic orientations. Our strain-dependent investigations, spanning both compressive and tensile deformations along in-plane and out-of-plane directions, uncovered nuanced variations in the nodal ring's energetic and spatial characteristics. The hourglass nodal ring state presented herein, coupled with the material's demonstrated stability, offers an unprecedented framework for future experimental explorations. By bridging theoretical predictions with practical accessibility, this research potentially illuminates novel pathways in topological materials design and quantum technological applications.