A Broken Translational Symmetry State in an Infinite-Layer Nickelate

TL;DR

This paper reports the discovery of a charge order in infinite-layer nickelates, revealing competing phases and strong electronic correlations relevant to understanding nickelate superconductivity.

Contribution

It uncovers a charge order in La1-xSrxNiO2, showing its origin from Ni 3d states and its evolution with doping, highlighting strong correlation effects.

Findings

Charge order observed along Ni-O bond direction with incommensurate wave vector.

Charge order diminishes with doping and shifts toward a commensurate wave vector.

Charge order likely arises from strong correlations, not Fermi surface nesting.

Abstract

A defining signature of strongly correlated electronic systems is the existence of competing phases with similar ground state energies, resulting in a rich phase diagram. While in the recently discovered nickelate superconductors, a high antiferromagnetic exchange energy has been reported, which implies the existence of strong electronic correlations, signatures of competing phases have not yet been observed. Here, we uncover a charge order (CO) in infinite-layer nickelates La1-xSrxNiO2 using resonant x-ray scattering across the Ni L-edge. In the parent compound, the CO arranges along the Ni-O bond direction with an incommensurate wave vector (0.344+/-0.002, 0) r.l.u., distinct from the stripe order in other nickelates which propagates along a direction 45 degree to the Ni-O bond. The CO resonance profile indicates that CO originates from the Ni 3d states and induces a parasitic charge modulation of La electrons. Upon doping, the CO diminishes and the ordering wave vector shifts toward a commensurate value of 1/3 r.l.u., indicating that the CO likely arises from strong correlation effects and not from Fermi surface nesting.