Hybridization in Ce-based heavy-fermion compounds in the vicinity of quantum criticality

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 CeTX series of compounds (T=transition metal, X=p-block element) have a ZrNiAl structure type with Ce atoms sitting on a distorted Kagome lattice. For the studied compounds, small changes in the unit cell volume drive the system into a variety of interesting ground states across a quantum critical point. CePdAl illustrates frustrated magnetism and is a candidate quantum spin liquid, whereas the mixed valent metals CeIrSn and CeRhSn, which are in closest proximity to the quantum critical point show a drastically increased Kondo temperature and strong Ising anisotropy at low temperatures. 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 Fourier-transformed infrared reflection spectroscopic measurements on a series of Ce-based compounds to study the evolution of the c-f hybridization across the quantum critical point.