Effect of polarity mismatch at chemically sharp interfaces on structure and superconductivity

Ascertain how the polarity mismatch at chemically sharp, non–B-site-intermixed interfaces in infinite-layer nickelate thin films influences the crystal structure, the electronic structure, and, consequently, the superconducting properties.

Background

Earlier studies often found an intermixed Ni/Ti perovskite-like interfacial layer in SrTiO3-based infinite-layer nickelate films, which reduces the interface polarity and was proposed as a universal interface configuration. However, recent synthesis advances and the present work demonstrate chemically sharp interfaces without Ni/Ti intermixing, implying a stronger interfacial polarity mismatch.

Theory has suggested distinct band alignments depending on substrate choice (n-type on SrTiO3 and p-type on NdGaO3), but prior to this paper there were no experimental observations of p-type interfaces in infinite-layer nickelates. Understanding how increased polarity mismatch at these chemically sharp interfaces alters local coordination, orbital hierarchy, and charge distribution—and how these changes feed back on superconductivity—remains a key unresolved issue.