Plethora of flat bands in a mixed-valence Ce-based pyrochlore lattice

Pyrochlore lattices, derived from the mineral pyrochlore, have long been a subject of interest in condensed matter physics due to their geometrically frustrated magnetic properties and potential for hosting exotic quantum states. In the context of electronic band structures, the potential emergence of flat bands in these lattices adds another layer of intrigue. In this study, we delve into the electronic structure of a cerium (Ce) based pyrochlore lattice. Using a blend of first-principles calculations and photoemission spectroscopy, we uncover the presence of both surface f-electron flat bands and d-orbital topological nontrival three dimensional flat bands in close proximity to the Fermi level. Meanwhile, our resonant ARPES measurement demonstrates the itinerant nature of the bulk 4f states, while the surface f electrons remains highly localized. Our transport measurement further reveals the the collaborative contribution of f-d hybridyzation and three-dimensional flat band in realizing the largest intrinsic AHE to date. Our work positions the mixed-valence Ce-based pyrochlore lattice as a promising avenue for exploring the intricate relationship between three-dimension flat band physics and electronic correlations, offering insights for the development of future quantum materials.