Abstract
The demonstration of superconductivity in nickelate analogs of high cuprates provides new perspectives on the physics of correlated electron materials. The degree to which the nickelate electronic structure is similar to that of cuprates is an important open question. This paper presents results of a comparative study of the many-body electronic structure and theoretical phase diagram of the isostructural materials and . Both and are found to be charge transfer materials. Important differences include the proximity of the oxygen bands to the Fermi level, the bandwidth of the transition metal-derived bands, and the presence, in , of both Nd-derived states crossing the Fermi level and a van Hove singularity that crosses the Fermi level as the out-of-plane momentum is varied. The low-energy physics of is found to be that of a single Ni-derived correlated band, with additional accompanying weakly correlated bands of Nd-derived states that dope the Ni-derived band. The effective correlation strength of the Ni-derived band crossing the Fermi level in is found to be greater than that of the Cu-derived band in , but the predicted magnetic transition temperature of is substantially lower than that of because of the smaller bandwidth.
- Received 31 January 2020
- Revised 23 March 2020
- Accepted 20 April 2020
DOI:https://doi.org/10.1103/PhysRevX.10.021061
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
The unconventional high-temperature superconductivity of layered copper oxide compounds has been of fundamental scientific interest for 35 years. Recent experimental reports of superconductivity in , a material in some respects structurally and electronically similar to the layered copper oxide superconductors, have sparked great excitement. The hope is that understanding ’s similarities and differences to the copper oxide superconductors will provide new insights into unconventional and high-temperature superconductivity. To that end, we use state-of-the-art theoretical models to compare the electronic structure of to the structurally similar copper oxide compound .
We find crucial similarities between these two compounds, including a very similar “charge-transfer” nature of the important electronic states, as well as significant differences, including that the magnitude of the charge-transfer energy is greater in the nickel compound than the copper analog. Also, in the nickel compound, the density-of-states enhancement referred to as a van Hove singularity occurs near the chemical potential, and the Fermi-surface shape has a noticeable dependence on momentum perpendicular to the planes; while in the copper compound, the van Hove singularity is somewhat removed in energy from the chemical potential, and the Fermi surface depends much less strongly on perpendicular momentum. The weakly correlated Nd-derived bands also present at the Fermi surface are found to be “spectators,” irrelevant to the correlation physics except insofar as they dope the Ni-derived bands.
We hope that further comparison of these compounds as well as subsequent theories built on this work will help unravel the secret of high-temperature superconductivity.