In photoemission experiments, 'waterfall'-like vertical spectral features are usually taken as signs of strong electron correlations or coupling to bosons. An international team has tested this link in the kagome metal LuFe6Ge6, using polarisation-dependent photoemission, density functional theory and dynamical mean-field theory.
They observed a pronounced vertical feature extending over several hundred meV, starting at a van Hove singularity about 0.3 eV below the Fermi level, yet the calculations show only weak correlations. The authors propose that the anomalous weight may come from inelastic scattering of the outgoing photoelectrons. QMAT's Junze Deng and Päivi Törmä of Aalto University co-authored the study with partners including DIPC, CIC nanoGUNE, Princeton University, Diamond Light Source and the Max Planck Institute for Chemical Physics of Solids.
The preprint has not yet been peer reviewed.
Figure: Lim et al., arXiv:2610.08356 (2026), CC BY 4.0