A broken translational symmetry state in an infinite-layer nickelate

A defining signature of strongly correlated electronic systems is a rich phase diagram, which consists of multiple broken symmetries, such as magnetism, superconductivity and charge order 1 , 2 . In the recently discovered nickelate superconductors 3 – 10 , a large antiferromagnetic exchange energy has been reported, which implies the existence of strong electronic correlations 11 . However, signatures of a broken-symmetry state other than superconductivity have not yet been observed. Here we observe charge ordering in infinite-layer nickelates La 1− x Sr x NiO 2 using resonant X-ray scattering. The parent compound orders along the Ni–O bond direction with an incommensurate wavevector, distinct from the stripe order observed in other nickelates 12 – 14 that propagates along a direction 45° to the Ni–O bond. The resonance profile we measure indicates that ordering originates from the nickelate layers and induces a parasitic charge modulation of lanthanum electrons. Upon doping, the charge order diminishes and its wavevector shifts towards commensurate, hinting that strong electronic correlations are likely to be responsible for the ordered state. Our results suggest that the existence of charge order and its potential interplay with antiferromagnetic fluctuations and superconductivity are important themes in nickel-based superconductors. Unconventional superconductivity is often associated with the presence of other kinds of electronic order. Observations of charge order in infinite-layer nickelate superconductors show that they fit this pattern.