Layered palladates and their relation to nickelates and cuprates

We explore the layered palladium oxides La$_2$PdO$_4$, LaPdO$_2$ and La$_4$Pd$_3$O$_8$ via ab initio calculations. La$_2$PdO$_4$, being low spin $d^8$, is quite different from its high spin nickel analog. Hypothetical LaPdO$_2$, despite its $d^9$ configuration, has a paramagnetic electronic structure very different from cuprates. On the other hand, the hypothetical trilayer compound La$_4$Pd$_3$O$_8$ ($d^{8.67}$) is more promising in that its paramagnetic electronic structure is very similar to that of overdoped cuprates. But even in the $d^9$ limit (achieved by partial substitution of La with a 4+ ion), we find that an antiferromagnetic insulating state cannot be stabilized due to the less correlated nature of Pd ions. Therefore, this material, if it could be synthesized, would provide an ideal platform for testing the validity of magnetic theories for high-temperature superconductivity.