Uncovering an Interfacial\nBand Resulting from Orbital\nHybridization in Nickelate Heterostructures

The interaction of atomic orbitals at the interface of\nperovskite\noxide heterostructures has been investigated for its profound impact\non the band structures and electronic properties, giving rise to unique\nelectronic states and a variety of tunable functionalities. In this\nstudy, we conducted an extensive investigation of the optical and\nelectronic properties of epitaxial NdNiO<sub>3</sub> synthesized on\na series of single-crystal substrates. Unlike nanofilms synthesized\non other substrates, NdNiO<sub>3</sub> on SrTiO<sub>3</sub> (NNO/STO)\ngives rise to a unique band structure featuring an additional unoccupied\nband situated above the Fermi level. Our comprehensive investigation,\nwhich incorporated a wide array of experimental techniques and density\nfunctional theory calculations, revealed that the emergence of the\ninterfacial band structure is primarily driven by orbital hybridization\nbetween the Ti 3d orbitals of the STO substrate and the O 2p orbitals\nof the NNO thin film. Furthermore, exciton peaks have been detected\nin the optical spectra of the NNO/STO film, attributable to the pronounced\nelectron–electron (e–e) and electron–hole (e–h)\ninteractions propagating from the STO substrate into the NNO film.\nThese findings underscore the substantial influence of interfacial\norbital hybridization on the electronic structure of oxide thin films,\nthereby offering key insights into tuning their interfacial properties.