ARPES study of Y₂O₂Bi single crystals: Intrinsic electronic structure of Bi square nets

The Bi square net, a structural motif in a diverse array of layered compounds, has emerged as a desirable system for investigating the interplay between strong spin–orbit coupling, reduced dimensionality, and magnetism. We present a comprehensive study of Y₂O₂Bi single crystals using high-resolution angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT) calculations to elucidate the intrinsic electronic structure of the Bi square net. Our findings reveal a pronounced two-dimensional character of the electronic states, with the Bi square net dominating the low-energy electronic structure. While Y₂O₂Bi itself exhibits no topological features, DFT calculations on related Bi square net compounds reveal that the surrounding crystal environment can induce non-trivial topology, as exemplified by the topological insulator LiBi. This comparative study establishes a crucial benchmark for understanding Bi square net physics and informs the design of future Bi square net-based quantum materials.