Abstract
The recent discovery of superconductivity in oxygen-reduced monovalent nickelates has raised a new platform for the study of unconventional superconductivity, with similarities and differences with the cuprate high temperature superconductors. In this paper we investigate the family of infinite-layer nickelates $R$NiO$_2$ with rare-earth $R$ spanning across the lanthanide series, introducing a new and non-trivial "knob" with which to tune nickelate superconductivity. When traversing from La to Lu, the out-of-plane lattice constant decreases dramatically with an accompanying increase of Ni $ d_{x^2-y^2}$ bandwidth; however, surprisingly, the role of oxygen charge transfer diminishes. In contrast, the magnetic exchange grows across the lanthanides which may be favorable to superconductivity. Moreover, compensation effects from the itinerant $5d$ electrons present a closer analogy to Kondo lattices, indicating a stronger interplay between charge transfer, bandwidth renormalization, compensation, and magnetic exchange. We also obtain the microscopic Hamiltonian using Wannier downfolding technique, which will provide the starting point for further many-body theoretical studies.
Highlights
In 1986, the discovery of high-temperature superconductivity in the copper oxide La2−xSrxCuO4 (LSCO) by Bednorz and Müller ushered in a new era in condensed matter research [1]
We investigate the family of infinite-layer nickelates RNiO2 with rare-earth R spanning across the lanthanide series, introducing a new and nontrivial “knob” with which to tune nickelate superconductivity
While there is no overall consensus on the physics at this stage, there is more or less general agreement on a few observations about the electronic structure in RNiO2: In the absence of strong interactions, the low-energy physics in the NiO2 layers is that of a single, holelike band crossing the Fermi energy; in the presence of strong interactions, the NiO2 layers become “Mott” insulating, such a state still involves a significant amount of oxygen character [20]; and unlike the cuprates, rather than sitting well above the Fermi energy, the rare-earth band forms small, but significant, metallic pocket(s) [18,19]
Summary
In 1986, the discovery of high-temperature superconductivity in the copper oxide (cuprate) La2−xSrxCuO4 (LSCO) by Bednorz and Müller ushered in a new era in condensed matter research [1]. Electronic structure in RNiO2: In the absence of strong interactions, the low-energy physics in the NiO2 layers is that of a single, holelike band crossing the Fermi energy; in the presence of strong interactions, the NiO2 layers become “Mott” insulating, such a state still involves a significant amount of oxygen character [20]; and unlike the cuprates, rather than sitting well above the Fermi energy, the rare-earth band forms small, but significant, metallic pocket(s) [18,19]. We present a microscopic Hamiltonian and effective parameters for representative compounds, which can serve as a starting point for more complex many-body calculations for specific materials and the infinite-layer rare-earth nickelate family, in general
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