Charge Order in Tunable Electronic Nematic Superconductor Ba1-xSrxNi2As2

Recent discoveries of charge order in the cuprates and electron nematic order in the iron-based superconductors has pointed towards the possibilities of both orderings being tied to mechanisms of high Tc superconductivity.The Ba(1-x)Sr(x)Ni2As2 system, closely related to the BaFe2As2 system, has recently been shown to exhibit both types of ordering without the presence of any magnetic order. We report single crystal X-ray diffraction observations that show a unidirectional charge order with wavevector (0.27,0,0) in BaNi2As2 decays and vanishes by x=0.65. We also show that the (0.33,0,0) CDW in the triclinic phase evolves into a (0.5,0,0) CDW by x=0.65. The evolution of the charge order in this system correlates well with the reported evolution of nematicity and superconducivity, suggesting a strong link between the three phases.