X-ray spectroscopic investigation of crystal fields in Ce2Rh1−xIrxIn8 heavy fermions

The higher dimensionality in the crystal fields of the Ce2MIn8 (M=Rh,Ir) compounds and its interplay with hybridization and disorder are key ingredients to understand the complex phase diagrams by this family, which have been explored extensively by macroscopic techniques. Here, we present an investigation of the crystal-electric field schemes of Ce2Rh1−xIrxIn8 using x-ray absorption spectroscopy. Our full multiplet calculations for the 4f1 configuration of Ce3+ to describe the temperature-dependent linear dichroism in Ce2MIn8 are consistent with a Γ71=1−α2·|∓32〉−|α|·|±52〉 ground state containing a predominant |±3/2〉 contribution that increases further with x. This enhancement is believed to favor superconductivity in Ce-based heavy fermion materials, observed in previous results in the CeMIn5 family. Our recent observations shed light on the unexpected emergence of the ambient-pressure superconducting dome in the center of the composition phase diagram and its subsequent suppression on the Ir-rich side due to the early onset of fluctuations associated with the structurally more disordered state, inferred from previous neutron magnetic diffraction experiments. Published by the American Physical Society 2024