Charge and spin stripe formation and dynamics in nickelates

Various nickelates, which have long been viewed as potential analogs to cuprate superconductors, host spin and charge stripe orders. Remarkably, superconductivity was discovered in the square-planar nickelate family, making the characterization and understanding of stripe orders in nickelates increasingly appealing. Here we use resonant x-ray photon correlation spectroscopy to study the temporal stability and domain memory of the stripe orders in La_2−xSr_xNiO_4+δ [1]. Temperature dependent fluctuations are observed for both the charge and spin stripes. Notably, charge order shows robust domain memory with thermal cycling up to 250 K, far above the ordering temperature, while the spin stripe speckle pattern loses reproducibility once the sample is warmed across the transition temperature. We extend our discussion to the square-planar La₄Ni₃O₈, in which similar diagonal charge and spin stripe orders form at low temperature, and make further comparison with the cuprates [2, 3].