Distinct Charge Orders in the Planes and Chains of Ortho-III-Ordered YBa2Cu3O6 identified by Resonant elas- tic x-ray scattering

Recently, charge density wave order with {\bf \it Q} = [0.3 0 $L$] and [0 0.3 $L$] was detected for the first time in underdoped YBCO using resonant soft x-ray scattering at the Cu $L_3$ absorption edge. Here, we explore the energy and polarization dependence of the resonant scattering intensity in detwinned YBa$_2$Cu$_3$O$_{6.75}$ with ortho-III oxygen ordering in the chain layer. We show that the ortho-III order results in a commensurate peak at $H$ = 0.33 whose energy and polarization dependence agrees with expectations for oxygen ordering in the chains. The [0.3 0 $L$] and [0 0.3 $L$] peaks, which result from a modulation of Cu 3$d_{x^2-y^2}$ states in the CuO$_2$ planes, are shown to be distinct and seemingly unrelated to the structure of the chain layer. Moreover, the energy dependence of the [0.3 0 $L$] and [0 0.3 $L$] scattering intensity is found to result from a spatial modulation of the energies of the Cu 2$p$ to 3$d_{x^2-y^2}$ transition, similar to stripe-ordered 214 cuprates.