Tunable charge order by pressure and isovalent substitution in electronic nematic superconducting system Ba(1-x)Sr(x)Ni2As2

The discoveries of charge order in the cuprates and nematic order in the iron-based superconductors have 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 in structure to the BaFe2As2 system, has been shown to exhibit both types of ordering without the presence of any magnetic order. We report single crystal X-ray diffraction that shows the evolution of two commensurate charge orderings and one incommensurate charge ordering in the Ba(1-x)Sr(x)Ni2As2 system. Additionally, we present pressure experiments that study the relationship between Sr substitution and applied pressure in order to understand the evolution of the phase diagram. The evolution of the charge order in this system correlates well with the already reported evolutions of nematicity and superconducivity, suggesting a strong link between the three phases.