Attaining the Obstructed Atomic Limit in an Orbital-Filtered Planar Kagome Monolayer

Kagome systems are known to host a range of exotic electronic features, including flat bands, Dirac fermions, and van Hove singularities. We theoretically investigate a monolayer model system with p-orbitals, where substrate-induced orbital filtering results in a two-orbital Kagome band structure near the Fermi level. Through topological quantum chemistry, we analyze symmetry-protected degeneracies and their evolution across the Brillouin zone, revealing key distinctions between the pristine and breathing phases. In both the cases, two irreducible representations of the site-symmetry group D_2h intricately hybridize, inducing a transition from pure to mixed Kagome states under symmetry-allowed Hamiltonian perturbations. Furthermore, Density functional theory and tight-binding calculations identify an obstructed atomic limit with a topological crystalline invariant and a large band gap induced by breathing distortion. Our analysis reveals a complex interplay between intrinsic and Rashba spin-orbit coupling, alongside band splittings induced by broken inversion. These theoretical predictions are strongly supported by ARPES and STM experiments on a "kagome" monolayer of Sb grown on SiC(0001), confirming the Kagome-derived band structure and a ~1.77 eV gap. Numerical simulations on open-boundary geometries demonstrate the tunability of corner states, suggesting a versatile platform for exploring crystalline topology and symmetry-protected phenomena in engineered 2D materials.