Impact of Cation Stoichiometry on the Crystalline Structure and Superconductivity in Nickelates

Abstract

The recent discovery of superconductivity in infinite-layer nickelate films has aroused great interest since it provides a new platform to explore the mechanism of high-temperature superconductivity. However, superconductivity only appears in the thin film form and synthesizing superconducting nickelate films is extremely challenging, limiting the in-depth studies on this compound. Here, we explore the critical parameters in the growth of high quality nickelate films using molecular beam epitaxy (MBE). We found that stoichiometry is crucial in optimizing the crystalline structure and realizing superconductivity in nickelate films. In precursor NdNiO3 films, optimal stoichiometry of cations yields the most compact lattice while off-stoichiometry of cations causes obvious lattice expansion, influencing the subsequent topotactic reduction and the emergence of superconductivity in infinite-layer nickelates. Surprisingly, in-situ reflection high energy electron diffraction (RHEED) indicates that some impurity phases always appear once Sr ions are doped into NdNiO3 although the X-ray diffraction (XRD) data are of high quality. While these impurity phases do not seem to suppress the superconductivity, their impacts on the electronic and magnetic structure deserve further studies. Our work demonstrates and highlights the significance of cation stoichiometry in superconducting nickelate family.

arXiv comment12 pages, 3 figures

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• Superconductivity in a quintuple-layer square-planar nickelate
• Character of the "normal state" of the nickelate superconductors
• Superconductivity in infinite-layer nickelates
• Absence of $3a_0$ Charge Density Wave Order in the Infinite Layer Nickelates
• Evidence for quasi-two-dimensional superconductivity in infinite-layer nickelates
• Topotactic Transition: A Promising Opportunity for Creating New Oxides
• Electronic Structure of Superconducting Infinite-Layer Lanthanum Nickelates
• Infinite-layer nickelate superconductors: A current experimental perspective of the crystal and electronic structures
• Synthesis and electronic properties of Nd${}_{n+1}$Ni${}_n$O${}_{3n+1}$ Ruddlesden-Popper nickelate thin films
• Soft X-ray Spectroscopy of Low-Valence Nickelates
• Strain-induced enhancement of $T_c$ in infinite-layer Pr${}_{0.8}$Sr${}_{0.2}$NiO${}_2$ films
• Limits to the strain engineering of layered square-planar nickelate thin films
• Synthesis and physical properties of LaNiO${}_2$ crystals
• Superconductivity in PrNiO2 infinite-layer nickelates
• Investigation of hydrogen incorporations in bulk infinite-layer nickelates
• Superconductivity in freestanding infinite-layer nickelate membranes
• Synthesis of thin film infinite-layer nickelates by atomic hydrogen reduction: clarifying the role of the capping layer
• $\text{In situ}$ preparation of superconducting infinite-layer nickelate thin films with atomically flat surface
• Large upper critical fields and dimensionality crossover of superconductivity in infinite-layer nickelate La${}_{0.8}$Sr${}_{0.2}$NiO${}_2$
• Thin-film aspects of superconducting nickelates
• Possible structural quantum criticality tuned by rare-earth ion substitution in infinite-layer nickelates
• Capping effects on spin and charge excitations in parent and superconducting Nd1-xSrxNiO2
• Superconducting phase diagram of multi-layer square-planar nickelates
• Chemical control of polymorphism and ferroelectricity in PbTiO3 and SrTiO3 monolayers and bilayers
• Achieving superconductivity in infinite-layer nickelate thin films by aluminum sputtering deposition