In operando adjustable orbital polarization in LaNiO3 thin films

Financial support from the Spanish Ministry of Science, Innovation and Universities, through the “Severo Ochoa” Program for Centers of Excellence in R&D (Grant No. SEV2015-0496) and Grant No. MAT2017-85232-R (AEI/FEDER, EU), and from Generalitat de Catalunya (Grant No. 2017 SGR 1377) is acknowledged. We thank Dr. Zhiwei Hu, Max-Planck-Institute for Chemical Physics of Solids, Germany for helpful discussions. The support and advice from Dr. F. Sanchez on the film growth and Dr. Ignasi Fina for ferroelectric characterization are very much appreciated.