Abstract
Here, we experimentally demonstrate a novel approach to substantially modify orbital occupations and symmetries in electronically correlated oxides. Rather than strain or confinement, this orbital tuning is achieved by exploiting charge transfer and inversion symmetry breaking using atomically layered, three-component heterostructures. We illustrate the technique with the three-component system of LaTiO3/LaNiO3/LaAlO3; a combination of x-ray absorption spectroscopy and ab initio theory reveals electron transfer, concomitant polar fields, and a resulting ~50% change in the occupation of Ni d orbitals. This change is sufficient to remove the orbital degeneracy found in bulk LaNiO3 and creates an electronic configuration approaching a single-band Fermi surface. Furthermore, we theoretically show that such three-component heterostructuring is robust and tunable by choice of insulator in the heterostructure, which provides a general means for engineering orbital configurations and designing novel electronic systems.
