Reconstructing the polar interface of infinite-layer nickelate thin films

Abstract

Nickel-based superconductors provide a long-awaited experimental platform to explore possible cuprate-like superconductivity. Despite similar crystal structure and $d$ electron filling, these systems exhibit several differences. Nickelates are the most polar layered oxide superconductor, raising questions about the interface between substrate and thin film -- thus far the only sample geometry to successfully stabilize superconductivity. We conduct a detailed experimental and theoretical study of the prototypical interface between Nd${}_{1-x}$Sr${}_x$NiO${}_2$ and SrTiO${}_3$. Atomic-resolution electron energy loss spectroscopy in the scanning transmission electron microscope reveals the formation of a single intermediate Nd(Ti,Ni)O${}_3$ layer. Density functional theory calculations with a Hubbard $U$ term show how the observed structure alleviates the strong polar discontinuity. We explore effects of oxygen occupancy, hole doping, and cation structure to disentangle the contributions of each for reducing interface charge density. Resolving the nontrivial interface structure will be instructive for future synthesis of nickelate films on other substrates and in vertical heterostructures.

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• A superconducting praseodymium nickelate with infinite layer structure
• Nickelate superconductivity without rare-earth magnetism: (La,Sr)NiO${}_2$
• Late transition-metal oxides with infinite-layer structure: Nickelates versus cuprates
• Charge density waves in infinite-layer NdNiO${}_2$ nickelates
• Charge and spin order dichotomy in NdNiO${}_2$ driven by SrTiO${}_3$ capping layer
• Polarity induced electronic and atomic reconstruction at NdNiO2/SrTiO3 interfaces
• Correlated interface electron gas in infinite-layer nickelate versus cuprate films on SrTiO${}_3$(001)
• Negligible oxygen vacancies, low critical current density, electric-field modulation, in-plane anisotropic and high-field transport of a superconducting Nd0.8Sr0.2NiO2/SrTiO3 heterostructure
• Magnetic excitations in infinite-layer nickelates

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• Limits to the strain engineering of layered square-planar nickelate thin films
• Superconductivity in PrNiO2 infinite-layer nickelates
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• Synthesis of thin film infinite-layer nickelates by atomic hydrogen reduction: clarifying the role of the capping layer
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• $\text{In situ}$ preparation of superconducting infinite-layer nickelate thin films with atomically flat surface
• Nature of the magnetic coupling in infinite-layer nickelates versus cuprates
• Unraveling p-type and n-type interfaces in Superconducting Infinite-Layer Nickelate thin films
• Rashba spin-orbit coupling in infinite-layer nickelate films on SrTiO3(001) and KTaO3(001)
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• Fermi surface reconstruction and enhanced spin fluctuations in strained La${}_3$Ni${}_2$O${}_7$ on LaAlO${}_3$(001) and SrTiO${}_3$(001)
• Electronic reconstruction and interface engineering of emergent spin fluctuations in compressively strained La${}_3$Ni${}_2$O${}_7$ on SrLaAlO${}_4$(001)
• Oxygen sublattice disorder and valence state modulation in infinite-layer nickelate superlattices
• Heteroanionic Stabilization of Ni${}^{1+}$ with Nonplanar Coordination in Layered Nickelates
• Achieving superconductivity in infinite-layer nickelate thin films by aluminum sputtering deposition
• Surfaces and interfaces of infinite-layer nickelates studied by dynamical mean-field theory