Imaging Kagome Anomalies with inveRse phOtoemission Spectroscopy

Objective

Kagome materials host a unique electronic landscape, including flat bands, Dirac points, and van Hove singularities (VHS), which underpin emergent phenomena such as unconventional superconductivity, anomalous Hall effect, and topological states. These features are typically investigated with angle-resolved photoemission spectroscopy (ARPES), yet many remain inaccessible because photoemission probes only occupied states and is blind to unoccupied bands above the Fermi level. Inverse-ARPES (ARIPES) is, at present, a scarcely developed technique which is not yet suitable to perform such studies. These technological and scientific gaps will be bridged by the IKAROS project. With IKAROS, I will contribute to the development of ARIPES, a revolutionary inverse-photoemission setup which will redefine the state of the art and will be built in the laboratory of Prof. Ghiringhelli at Politecnico di Milano. Then, I will realize the first high-resolution, momentum-resolved mapping of the full bandstructure—including unoccupied states—of representative Kagome compounds using direct and inverse photoemission spectroscopy. The study targets three complementary systems: the prototypical CsV₃Sb₅ which hosts Dirac cones and VHS slightly above the Fermi level; FeSn, whose structure gives rise to an isolated flat band above the Fermi level, to characterize its width and quantify the electronic correlations; and Nb₃Cl₈, a new van-der-Waals Kagome material with strong correlations and thickness-dependent properties, to track the evolution of the Mott gap from the insulating bulk to the metallic monolayer. By combining ARPES and ARIPES, IKAROS will remove a critical blind spot in Kagome spectroscopy, delivering a comprehensive, momentum-resolved picture of occupied and unoccupied electronic states. Technologically, it will provide the first scientific demonstration of next-generation ARIPES, setting a new milestone in photoemission spectroscopy.