Correlation between ground state and orbital anisotropy in heavy fermion materials

Significance The ground state of materials with strong electronic correlations depends on a delicate balance among competing interactions. The strongly correlated compounds Ce M In 5 , with M = Co, Rh, and Ir, exhibit superconducting and magnetic ground states as well as Fermi surface changes upon substituting one M element for another and become even higher temperature superconductors when Ce is substituted by Pu. They are therefore recognized as important model systems in which a search for parameters correlating with the occurrence of these ground states could be successful. The present X-ray absorption study of CeRh 1− x Ir x In 5 reveals that anisotropy of the Ce 4 f -wave function is a significant parameter that is highly sensitive to the ground-state formation and should be taken into account when modeling these systems.