Knowledge

1 linked paper

Lattice-Charge Coupling in a Trilayer Nickelate with Intertwined Density Wave Order

We performed a systematic comparison of the two polytypes of La3Ni2O7—the alternating monolayer-trilayer LNO-1313 and the bilayer LNO-2222—and the trilayer compound La4Ni3O10 using Ni L3-edge and O K-edge resonant inelastic X-ray scattering (RIXS). We find that the electronic, magnetic, and lattice excitations of LNO-1313 and La4Ni3O10 are highly similar, whereas bilayer LNO-2222 exhibits distinctly different features. Compared with LNO-2222, LNO-1313 and La4Ni3O10 possess weaker orbital polarization, enhanced 3d^8 L (ligand-hole) character, a smaller out-of-plane magnetic exchange scale, and stronger electron-phonon coupling. Within an effective local-moment framework, the spin excitations arising from strong antiferromagnetic interlayer coupling can be naturally described by an entangled-dimer picture, whose advantage is most evident in bilayer LNO-2222, where the interlayer coupling exceeds the intralayer interactions. These results provide key experimental constraints for theoretical models of the low-energy physics relevant to superconductivity in layered nickelates.

3 linked papers

Based on a first-principles-derived two-orbital model, this study investigates the mechanism of topological superconductivity in substrate-supported bilayer nickelate thin films (La₃Ni₂O₇). Under the assumption of dominant interlayer pairing, the substrate-induced layer-asymmetric potential and layer-staggered Rashba spin-orbit coupling drive the system into a time-reversal-invariant topological superconducting phase of class DIII, which is protected by diagonal mirror symmetry. This nontrivial topology originates from the reversal of the pairing sign on the spin-split bonding Fermi surface, manifesting as a nonzero diagonal mirror winding number and Majorana Kramers pairs at the [11] edge. Furthermore, orbital hybridization gives rise to bulk Dirac nodes and zero-energy flat bands that deviate from the diagonal direction. The research establishes the potential of bilayer nickelates as a platform for topological superconductivity, where tunable topological transitions and boundary modes provide a new avenue for probing unconventional pairing.

This study employs density functional theory combined with dynamical mean-field theory (DFT+DMFT) to systematically analyze the layer-resolved electronic structure and correlation effects in low-n tetragonal nickelates. The results reveal that the electronic correlation strength of Ni-d orbitals in undoped systems increases with layer number, and that the inner NiO₂ planes consistently exhibit stronger correlations than the outer ones, a discrepancy originating from the inhomogeneous spatial charge distribution. For the n=2 and n=3 compounds, which are non-superconducting due to excessive hole doping, an electronic compensation strategy via Cl substitution at spacer-layer oxygen sites is proposed, and virtual crystal approximation simulations tune the nominal Ni valence to match that of the optimally superconducting n=6 system. Calculations demonstrate that Cl doping significantly enhances the Ni-d mass enhancement factor in the low-layer-number systems, driving them into the strongly correlated metallic regime while preserving the low-energy electronic structure. This work highlights the critical role of layer-resolved electronic correlations in the superconductivity mechanism and predicts that spacer-layer Cl doping is a viable pathway to convert low-n tetragonal nickelates into potential superconducting candidates.

4 linked papers

4 linked papers

8 linked papers

4 linked papers