Quadratic Nodal Point Phonons in a 2D Binary Indium Dinitride

Abstract In recent years, the exploration of topological phononic states in 2D materials has become a key research area. This study presents a systematic analysis of the distinctive topological characteristics in the monolayer binary compound InN 2 . Within its phononic spectrum, prominent topological band crossings are observed in two optical branches, corresponding to two quadratic nodal points localized at the M and Γ points. A thorough examination of the underlying mechanisms governing band formation and dispersion conditions has been conducted. Notably, the edge states associated with these quadratic nodal points are clearly resolved. These states exhibit two critical properties: they are spatially well‐separated from bulk band projections, and they display extensive spatial distributions—attributes that significantly enhance their experimental detectability and practical utility. To further advance the material's application potential, this work also characterizes its mechanical properties, revealing significant anisotropic behavior in key parameters. Collectively, the identification of these ideal topological quadratic nodal point states, combined with the material's inherent stability, provides a robust foundation for future experimental verification. This investigation is poised to accelerate progress in the rapidly developing field of 2D topological materials, offering new insights that may facilitate breakthroughs in phononic device design and topological quantum applications.