Optimizing superconductivity: from cuprates via nickelates to palladates

TL;DR

This study investigates the conditions for high-temperature superconductivity in single-band Hubbard models, identifying palladates as promising candidates based on theoretical calculations and first principles analysis.

Contribution

It provides a comprehensive analysis of superconducting instability across different materials, highlighting palladates as optimal candidates for high $T_c$ superconductivity.

Findings

Optimal $T_c$ occurs at intermediate coupling and low hole doping.

Nickelates and cuprates are not near the optimal conditions within the single-band model.

Certain palladates are identified as nearly ideal for high-temperature superconductivity.

Abstract

Motivated by cuprate and nickelate superconductors, we perform a comprehensive study of the superconducting instability in the single-band Hubbard model. We calculate the spectrum and superconducting transition temperature $T_{\rm c}$ as a function of filling and Coulomb interaction for a range of hopping parameters, using the dynamical vertex approximation. We find the sweet spot for high $T_{\rm c}$ to be at intermediate coupling, moderate Fermi surface warping, and low hole doping. Combining these results with first principles calculations, neither nickelates nor cuprates are close to this optimum within the single-band description. Instead, we identify some palladates, notably RbSr$_2$PdO$_3$ and $A^{\prime}_2$PdO$_2$Cl$_2$ ($A^{\prime}$=Ba$_{0.5}$La$_{0.5}$), to be virtually optimal, while others, such as NdPdO$_2$, are too weakly correlated.