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This study investigates waterfall-like spectral features in the kagome metal LuFe6Ge6 using ARPES, DFT, and DMFT. A prominent vertical spectral feature near the L point, primarily of Fe $d_{yz}$ character, coincides with a van Hove singularity but exhibits weak electronic correlations according to DMFT. The research proposes that this anomalous spectral weight may originate from inelastic scattering of photoelectrons, challenging the assumption that such features solely indicate strong electronic correlations.
Waterfall spectral features in kagome metals can emerge from van Hove singularities and photoelectron scattering, not just strong correlations.
Waterfall-like spectral features observed by angle-resolved photoemission spectroscopy (ARPES) are commonly associated with strong electronic correlations or electron-boson coupling. Here, we investigate this connection in the kagome metal LuFe6Ge6, a structurally simple member of the FeGe-derived family, using polarization-dependent ARPES, density functional theory and dynamical mean-field theory. We observe a pronounced vertical spectral feature at the L point extending over several hundred meV in binding energy. Its orbital character is identified as predominantly Fe dyz, and its energy onset coincides with a van Hove singularity located approximately 0.3 eV below EF . Despite the waterfall-like spectral response, dynamical mean-field theory (DMFT) reveals only weak electronic correlations, while the calculated electronic structure closely reproduces the experimental bulk bands. We propose that the anomalous spectral weight may arise from inelastic scattering of the outgoing photoelectrons, potentially associated with the large density of states near the van Hove singularity. Our results suggest that waterfall-like features can emerge without strong electronic correlations and highlight the possible role of the underlying band structure and photoelectron energy-loss processes in their interpretation.