Knowledge

6 linked papers

3 linked papers

2 linked papers

This study employs a multi-orbital itinerant electron framework, combined with Hartree-Fock and random phase approximation methods, to systematically analyze the magnetic ground states and transverse spin excitations of bilayer and trilayer nickelates. For the bilayer system, although the double-stripe order has slightly lower energy, the excitation spectrum of the single-stripe state exhibits anisotropic low-energy cone-shaped dispersion at the wavevector Q_BL and isotropic high-energy excitations near the Γ point, showing qualitative consistency with resonant inelastic X-ray scattering and neutron scattering experiments; it is also found that the energy of the mirror-even interlayer optical mode at Q_BL coincides with that of the mirror-odd mode at Γ. In the trilayer system, both mirror-odd and mirror-even spin-density wave orders can be stabilized, with the mirror-odd state having lower energy and hosting a near-zero-gap mode predominantly from the middle layer, whereas the mirror-even state supports only one acoustic mode and two gapped optical modes; comparison with experimental data supports the mirror-odd order picture. The results demonstrate that magnetic excitations can serve as a sensitive probe to distinguish magnetic order configurations and reinforce the conclusion that the magnetism in multilayer nickelates shares a common itinerant origin.

7 linked papers

2 linked papers

8 linked papers

Based on experimental evidence of orbital-selective electronic correlations, this work proposes a new magnetic description framework for bilayer nickelate La₃Ni₂O₇. In the bad-metal regime of the normal state, the system lies close to an orbital-selective Mott phase, with the electronic spectrum decomposing into coherent d_(x²-y²) quasiparticles and incoherent d_(z²) local moments. An effective spin model incorporating superexchange between local moments and RKKY interactions mediated by coherent electrons is constructed, where the RKKY contribution dominates third-neighbor coupling and introduces magnetic frustration. The model naturally stabilizes a noncoplanar antiferromagnetic ground state with a wavevector near (π/2, π/2) and antiferromagnetic interlayer stacking, consistent with neutron scattering experiments. The calculated spin-wave spectrum contains low-frequency acoustic and high-frequency optical branches, with the acoustic branch softening at the ordering wavevector and an overall bandwidth of about 80 meV, in agreement with resonant inelastic X-ray scattering data. These results reveal that orbital-selective correlations are the essential ingredient determining magnetism in bilayer nickelates and indicate that low-energy magnetic fluctuations and short-range exchange interactions may provide the pairing glue for unconventional superconductivity.

4 linked papers

5 linked papers