Anisotropic hybridization in Ce-based heavy-fermion compounds

The f-electrons of cerium hybridize with conduction electrons to produce coherent heavy bands at low temperatures, which dictates the ground state properties of the system. The studied mixed-valent compounds CeRhSn and CeIr₃B₂ with Ce atoms sitting on a (distorted) Kagome lattice in the ab-plane both stand out by drastically enhanced Kondo temperatures and strong magnetic frustration. To find the key drivers for the development of the ground state the hybridization and effective mass is analyzed by resolving the anisotropy between the ab-plane and c-axis, and in terms of reduced dimensionality in CeIr₃B₂ compared to CeRhSn. Whereas neighboring Ce atoms have similar distances within the ab-plane and the c-axis in the 3-dimensional CeRhSn, the distance in CeIr₃B₂ is considerably smaller along the c-axis, creating quasi one-dimensional Ce chains. A direct and quantitative probe of the hybridization gap generated by the c-f hybridization is provided by infrared absorption experiments. Here we present our results from temperature-dependent and polarization-resolved Fourier-transformed infrared reflection spectroscopic measurements on Ce-based compounds to study the evolution of the anisotropic c-f hybridization and the concomitant effective mass generation.