Correlated interface electron gas in infinite-layer nickelate versus cuprate films on SrTiO$_3$(001)

Abstract

Based on first-principles calculations including a Coulomb repulsion term, we identify trends in the electronic reconstruction of ANiO2/SrTiO3(001) (A = Pr, La) and ACuO2/SrTiO3(001) (A = Ca, Sr). Common to all cases is the emergence of a quasi-two-dimensional electron gas (q2DEG) in SrTiO3(001), albeit the higher polarity mismatch at the interface of nickelates vs. cuprates to the nonpolar SrTiO3(001) substrate (3+/0 vs. 2+/0) results in an enhanced q2DEG carrier density. The simulations reveal a significant dependence of the interfacial Ti 3dxy band bending on the rare-earth ion in the nickelate films, being 20-30% larger for PrNiO2 and NdNiO2 than for LaNiO2. Contrary to expectations from the formal polarity mismatch, the electrostatic doping in the films is twice as strong in cuprates as in nickelates. We demonstrate that the depletion of the selfdoping rare-earth 5d states enhances the similarity of nickelate and cuprate Fermi surfaces in film geometry, reflecting a single hole in the Ni and Cu 3d x 2 −y 2 orbitals. Finally, we show that NdNiO2 films grown on a polar NdGaO3(001) substrate feature a simultaneous suppression of q2DEG formation as well as Nd 5d self-doping.