Strain-controlled band engineering and Self-doping in Ultrathin LaNiO3 films

We discover a unique self-doping carrier transition by strain-induced in LaNiO$_3$ ultra thin film. Transport properties evolving from compressive to tensile strains are similar to those of different hole-doping superconducting cuprates. DFT calculations show the changes in low-energy electronic band structure account for the charge transfer between O p and Ni d states. The results indicate that ultrathin films can be used to change the carrier concentration transition metal oxides without resorting to chemical substitution.