Quantitative determination of bond order and lattice distortions in nickel oxide heterostructures by resonant x-ray scattering

TL;DR

This study combines resonant x-ray scattering and density functional calculations to distinguish electronically driven ordering from lattice distortions in nickelate heterostructures, revealing dominant spin density wave order in metallic nickelates.

Contribution

It provides a novel combined experimental and computational approach to separate electronic and structural effects in nickelate heterostructures, confirming the dominance of spin density wave order.

Findings

Structural distortions significantly affect Bragg peak intensities.

An upper bound on the bond-order parameter was established.

Spin density wave order is confirmed as dominant in metallic nickelates.

Abstract

We present a combined study of Ni $K$-edge resonant x-ray scattering and density functional calculations to probe and distinguish electronically driven ordering and lattice distortions in nickelate heterostructures. We demonstrate that due to the low crystal symmetry, contributions from structural distortions can contribute significantly to the energy-dependent Bragg peak intensities of a bond-ordered NdNiO$_3$ reference film. For a LaNiO$_3$-LaAlO$_3$ superlattice that exhibits magnetic order, we establish a rigorous upper bound on the bond-order parameter. We thus conclusively confirm predictions of a dominant spin density wave order parameter in metallic nickelates with a quasi-two-dimensional electronic structure.