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 $\mathrm{LaNi}{O}_3$ 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 $L_{2,3}$ edges. The voltage-controlled orbital polarization allows changing the orbital polarization by about an additional 50%.