Temperature-dependent electronic structure of EuNi2P2 revealed by angle-resolved photoemission spectroscopy

We studied the electronic structure of EuNi2P2, which exhibits both heavy-fermion and mixed-valence behaviors, using angle-resolved photoemission spectroscopy. Multiple Ni 3d bands were observed near the Fermi energy, and one of them forms a hole-like Fermi surface around the X point of the Brillouin zone. We also found that the spectral weight of the Ni 3d states is rapidly enhanced with decreasing temperature, which is consistent with the temperature dependence of the mean valence of Eu ions. Our results thus demonstrate hybridization between the Ni 3d and Eu 4f electrons in EuNi2P2.