Phase diagram of nickelate superconductors calculated by dynamical vertex approximation
Abstract
We review the electronic structure of nickelate superconductors with and without effects of electronic correlations. As a minimal model we identify the oneband Hubbard model for the Ni 3d x 2 −y 2 orbital plus a pocket around the Amomentum. The latter however merely acts as a decoupled electron reservoir. This reservoir makes a careful translation from nominal Sr doping to the doping of the oneband Hubbard model mandatory. Our dynamical meanfield theory calculations, in part already supported by experiment, indicate that the Γ pocket, Nd 4f orbitals, oxygen 2p and the other Ni 3d orbitals are not relevant in the superconducting doping regime. The physics is completely different if topotactic hydrogen is present or the oxygen reduction is incomplete. Then, a twoband physics hosted by the Ni 3d x 2 −y 2 and 3d 3z 2 −r 2 orbitals emerges. Based on our minimal modeling we calculated the superconducting T c vs. Srdoping x phase diagram prior to experiment using the dynamical vertex approximation. For such a notoriously difficult to determine quantity as T c , the agreement with experiment is astonishingly good. The prediction that T c is enhanced with pressure or compressive strain, has been confirmed experimentally as well. This supports that the oneband Hubbard model plus an electron reservoir is the appropriate minimal model.
 Publication:

Frontiers in Physics
 Pub Date:
 January 2022
 DOI:
 10.3389/fphy.2021.810394
 arXiv:
 arXiv:2201.01220
 Bibcode:
 2022FrP.....9..803H
 Keywords:

 electronic structure calculations;
 Dynamical mean field theory;
 Electronic correlation;
 hightemperature superconductivity;
 Solid state theory;
 Condensed Matter  Superconductivity;
 Condensed Matter  Strongly Correlated Electrons
 EPrint:
 20 pages