Obstructed atomic insulator is recently proposed as an unconventional material, in which electric charge centers localized at sites away from the atoms. A half-filling surface state would emerge at specific interfaces cutting through these charge centers and avoid intersecting any atoms. In this article, we utilized photoemission spectroscopy and density functional theory calculations to study one of the obstructed atomic insulator candidates, NiP₂. A floating surface state with large effective mass that is close to the Fermi level and isolated from all bulk states is resolved on the (100) cleavage plane, implying better catalytic activity in this plane than the previously studied surfaces. Density functional theory calculation results elucidate that this floating surface state is originated from the obstructed Wannier charge centers, albeit underwent surface reconstruction. Our findings not only shed lights on the study of obstructed atomic insulators, but also provide possible route for development of new catalysts.

阻塞原子绝缘体最近被提议作为一种非常规材料，其中电荷中心位于远离原子的位置。半填充表面状态将在穿过这些电荷中心的特定界面处出现，并避免与任何原子相交。在本文中，我们利用光电子能谱和密度泛函理论计算来研究阻塞原子绝缘体候选者之一 NiP₂。在 （100） 解理面上解析出接近费米能级并与所有体态隔离的大有效质量的浮动表面态，这意味着该平面中的催化活性优于先前研究的表面。密度泛函理论计算结果阐明，这种浮动表面状态起源于被阻塞的 Wannier 电荷中心，尽管经历了表面重构。我们的发现不仅为阻塞原子绝缘体的研究提供了启示，而且为开发新型催化剂提供了可能的途径。