Role of interface polarity in the electronic reconstruction of infinite-layer vs. perovskite nickelate films on SrTiO₃(001)

Motivated by the recent observation of superconductivity in the infinite-layer nickelate NdNiO₂ on SrTiO₃(001) by Li et al. [1], we explore the effect of interface polarity on the electronic properties of NdNiO_n/SrTiO₃(001) and LaNiO_n/SrTiO₃(001) thin films (n=2,3) by performing first-principles calculations including a Coulomb repulsion term. For infinite-layer nickelate films (n=2), electronic reconstruction drives the emergence of a 2DEG at the interface due to a strong occupation of the Ti 3d states. This effect is more pronounced than in the paradigmatic LaAlO₃/SrTiO₃(001) system and accompanied by a substantial reconstruction of the Fermi surface. We contrast our findings with results for the perovskite compounds (n=3). Moreover, we analyze the topotactic reaction from a perovskite to an infinite-layer heterostructure and show why the reduction is confined to the nickelate film, whereas the SrTiO₃ substrate remains intact.

[1] D. Li et al., Nature 572, 624 (2019)