Two-Band Nodal Line Structure with Robust Surface States in the Cubic Na₃PdCl₆ Compound

Recent advancements in topological states have expanded from insulators to semimetals and metals, characterized by band crossings near the Fermi level. In this study, we use first-principles calculations and crystal symmetry analysis to uncover a complex nodal structure in cubic compound Na₃PdCl₆. This structure, formed by only two bands, features six intersecting butterfly-like nodal lines on the (110) surface, protected by mirror symmetry M ₁₁₀. The associated surface states span the entire Brillouin zone, enhancing the experimental observability. Remarkably, this nodal line configuration remains robust under both Hubbard correction and spin-orbit coupling effects, highlighting Na₃PdCl₆ as a promising material for both research and applications. To further provide a practical reference, the stabilities of Na₃PdCl₆ have been verified from different perspectives and several important mechanical parameters have been derived. The well-defined band structure, simple topological configuration, and robust surface state render Na₃PdCl₆ a compelling candidate for both theoretical exploration and experimental validation, suggesting significant potential for further research and potential applications.