RIXS study of the Anderson Lattice compound CePd₃

Intermediate valence (IV) materials represent one of the longest standing issues in quantum materials physics. In CePd₃, the correlation of localized and itinerant electrons results in an ambivalent state that strongly fluctuates between the Ce⁴⁺ (4f ⁰) and Ce³⁺ (4f ¹) configurations. The most striking manifestation of this Kondo hybridization of 4f electrons with a sea of transition metal states occurs at low temperatures, where the valence fluctuations may develop coherency. The few available neutron spectroscopic studies of such coherent “Anderson Lattices” have revealed that the phenomenon is associated with unusual quasiparticle excitations across the hybridization gap. The dynamic magnetic susceptibility thus acquires a characteristic energy-/momentum-space texture. The recent advances in soft x-ray resonant inelastic scattering (RIXS) are among the most anticipated developments at 3^rd generation synchrotrons. With an energy resolution on the order of E/dE=30000, soft RIXS is now able to address the small energy scale of the IV phenomenon. We present the first use of Ce M-edge RIXS to reveal the evolution of a low-temperature coherently hybridized state in CePd₃.