Discovery of an Ideal Quadratic Nodal Point in Two-Dimensional Binary Compound C₅P₁

Recent years have witnessed a surge in research focus on topological states within two-dimensional materials, emerging as a pivotal complement to studies on three-dimensional systems. This work presents a comprehensive investigation into the exceptional topological characteristics of the C₅P₁ monolayera binary compound whose electronic structure and topological behavior have been systematically explored through computational analysis. The material exhibits a simple electronic configuration featuring merely two bands proximate to the Fermi energy, with their crossing phenomena giving rise to a distinct quadratic nodal point, a hallmark topological attribute. Detailed investigations into the band formation mechanisms and dispersion characteristics were undertaken to clarify the fundamental origins of the observed topological phenomena. Of particular significance are two distinct edge states emerging from the nodal point and extending continuously toward the nodal line, exhibiting pronounced spatial delocalization along the material's interface. The C₅P₁ monolayer's incorporation of lightweight elements contributes decisively to the exceptional stability of both its topological features and corresponding edge states upon inclusion of spin-orbit coupling effects. Furthermore, to assess the potential for practical application, the strain-dependent modulation of these topological bands was systematically probed, alongside a thorough characterization of the material's subtle mechanical anisotropy. These analyses provide critical insights into how external perturbations modulate topological behavior, offering guidance for experimental synthesis and device integration. Taken together, the comprehensive analysis of this prototypical topological phase, along with the demonstrated intrinsic stability of the material, lays a robust foundation for forthcoming experimental verification. This study significantly advances the dynamic field of two-dimensional topological materials, opening new pathways for innovation in the design of quantum devices and deepening our understanding of topological phenomena.