In operando adjustable orbital polarization in LaNiO3 thin films

The different occupancy of electronic orbitals, the so-called orbital polarization, is a key parameter determining electric and magnetic properties of materials. Here we report on the demonstration of in operando voltage-controlled tuning of the orbital occupation in LaNiO3 epitaxial thin films grown on piezoelectric substrates. The different static contributions to the orbital occupation are disentangled, namely the epitaxial strain and the surface symmetry breaking, and the superimposed electric-field controlled orbital polarization are determined by x-ray linear dichroism at the Ni L-2,L-3 edges. The voltage-controlled orbital polarization allows changing the orbital polarization by about an additional 50%.