Ni2As2

Studies in the Cuprates and the Fe-based superconductors have hinted at a relationship between charge order order and superconductivity. The recent study on Ba_1-xSr_xNi₂As₂ shows strong nematic susceptibility for the B1G symmetry with increasing Sr doping corresponding to an enhancement in Tc. Ba_0.6Sr_0.4Ni₂As₂ is at the border of lattice driven nematic order and electronically driven nematic order. We report on X-ray and Neutron measurements on Ba_0.6Sr_0.40Ni₂As₂ that show the existence of three charge density waves. An incommensurate CDW in the tetragonal phase with q=(0.27,0,0) and two commensurate CDWs in the triclinic phase with q=(0.33,0,0) and (0.5,0,0) are observed. The commensurate CDWs in the triclinic phase exist down to base temperature. We will discuss these results as well as elastoresistance measurements in Ba_0.6Sr_0.4Ni₂As₂.