Role of the interface for superconductivity in infinite-layer nickelate films*

The stabilization of superconducting infinite-layer nickelates [1] provides a long-awaited experimental platform to explore a close analogue of the high-T_c cuprates. As the family of superconducting nickelate thin films grows [2-4], superconductivity remains unreported in bulk samples, raising questions about the origin of superconductivity in these samples. In particular, the polar interface between the SrTiO₃ substrate and RNiO₂ (R = rare earth) films has been proposed to host a two-dimensional electron gas (2DEG) with very high carrier density [5]. Leveraging high-resolution electron energy loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM), we reveal the atomic-scale lattice structure and charge distribution at the nickelate-substrate interface. Informed by systematically varied theoretical models, we provide a more complete understanding of the role played by this interface for superconductivity. 

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

2. Osada, M. et al. Nano Lett. 20, 5735 (2020).

3. Osada, et al. Advanced Materials, 2104083 (2021).

4. Pan, et al. Nature Materials, in press (2021).

5. Geisler & Pentcheva, Phys. Rev. B 102, 020502 (2020).