A semiempirical approach for modeling heavy-fermion bands in f-materials

Developing a framework that provides access to the momentum-resolved fine electronic structure of strongly correlated f-electron materials is central to understanding the microscopic mechanisms governing their low-temperature properties. In Ce- and Yb-based heavy-fermion compounds, subtle features arising from crystal-electric-field (CEF)-split 4f states and their hybridization with itinerant bands govern low-energy phenomena, but a detailed, momentum-resolved mapping of these spectral features has so far remained elusive. Here, we present a computational approach that accurately describes the momentum-dependent hybridization of CEF-split 4f states with itinerant electrons, exemplified for two canonical heavy-fermion materials, YbRh2Si2 and YbIr2Si2. The method is based on prior knowledge of the CEF parameters, the energies of the 4f states, and the valency, which must be determined experimentally. Our approach reproduces both surface- and bulk-related 4f hybrid bands, with the computed f-derived Fermi surface in excellent agreement with momentum-resolved photoemission data. It provides access to subtle f − spd hybrid features in regions of the Brillouin zone that are challenging to access experimentally. While demonstrated for Yb-based systems, this framework can be extended to other lanthanide and actinide compounds, providing a general tool to guide and complement experiments and reveal the complex f-electron spectral structure that governs f-driven phenomena in strongly correlated materials. Accessing the momentum-resolved electronic structure of strongly correlated f-electron materials is crucial for understanding their low-temperature properties. Here, the authors introduce a computational framework that accurately maps the hybridization of crystal-field-split 4f states with itinerant electrons, aligning well with experimental data and offering insights into complex f-electron interactions across various compounds.