Single-layer T'-type nickelates: Ni 1 + is Ni 1 +

The discovery of superconductivity in the infinite-layer nickelates has opened new perspectives in the context of quantum materials. We analyze, via first-principles calculations, the electronic properties of ${\mathrm{La}}_{2}{\mathrm{NiO}}_{3}\mathrm{F}$---the first single-layer T'-type nickelate---and compare these properties with those of related nickelates and isostructural cuprates. We find that ${\mathrm{La}}_{2}{\mathrm{NiO}}_{3}\mathrm{F}$ is essentially a single-band system with a Fermi surface dominated by the Ni-$3{d}_{{x}^{2}\ensuremath{-}{y}^{2}}$ states with an exceptional 2D character. In addition, the hopping ratio is similar to that of the highest ${T}_{c}$ cuprates and there is a remarkable ${e}_{g}$ splitting together with a charge transfer energy of 3.6 eV. According to these descriptors, along with a comparison to ${\mathrm{Nd}}_{2}{\mathrm{CuO}}_{4}$, we thus indicate single-layer T'-type nickelates of this class as very promising analogs of cupratelike physics while keeping distinct ${\mathrm{Ni}}^{1+}$ features.