Juraj Krsnik and Prof. Karsten Held from TU Wien published an article in the journal Nature Communications, where they investigated the mechanism behind waterfall-like features in angle-resolved photoemission spectroscopy (ARPES) spectra, offering insights that these features originate from local electron correlations.
Krsnik and K. Held, Nat. Commun. 16, 255 (2025).
DOI: 10.1038/s41467-024-55465-7
Superconducting cuprates and nickelates, among other strongly correlated materials, quite universally exhibit a high-energy anomaly in their ARPES spectra in the form of a waterfall-like structure. Specifically, in the energy range of roughly 0.1 to 1 eV, the ARPES spectrum is characterized by an almost vertical energy-momentum dispersion and significant spectral broadening. In this study, these experimentally observed features are investigated using the dynamical mean-field theory (DMFT) approach to the Hubbard model, which nonperturbatively accounts for strong local electron correlations. The findings suggest that waterfall-like structures in the electron spectral function naturally-and even necessarily-emerge in a process where a Hubbard band develops and splits off from the quasiparticle band. Results obtained for the Hubbard model with ab initio determined parameters align well with measured waterfall-like features in cuprates and nickelates, providing a compelling and natural explanation for these spectral anomalies in correlated materials.
