Orbital structure of charge density waves in BaNi2As2

BaNi2As2 is a structural, but non-magnetic, homologue of the parent compound of the Fe-based superconductors BaFe2As2. An incommensurate charge density wave (I-CDW) and commensurate CDW (C-CDW) are observed next to an orthorhombic and triclinic structural transition, respectively. Even though the formation of the I-CDW is related to a complete softening of an optical phonon branch it is seen to be of unconventional nature. Elastoresitance measurements reveal an electronic nematic phase suggesting this system to be candidate system for charge-driven electronic nematicity. Recent near edge x-ray absorption fine structure measurements show a connection of the CDWs with orbital ordering, suggesting that nematicity could rise from orbital fluctuations. We propose to carry out polarization dependent resonant inelastic x-ray scattering (RIXS) study of the CDWs reflections at the Ni L3 edge (~852.8 eV) to investigate the orbital structure of the CDWs.