Hybridization between 4f-5d states in ErAs(100)

Generally in both elemental and compound rare earth systems, the 4f levels are treated as core states with little interaction with the 5d hybrid conduction and valence band states. In the present study, the band dispersions of the rare-earth pnictide erbium arsenide (ErAs) are observed to be perturbed from this expectation. Both photoemission symmetry selection rules and ab initio calculations provide evidences of the 4f-5d hybridization. This finding is also supported by the f-f resonant transition excitation energy shifts in characteristic electron-energy-loss spectroscopy (EELS).