Charge-orbital-lattice coupling effects in the d d excitation profile of one-dimensional cuprates

We identify dd excitations in the quasi-one-dimensional compound Ca ₂Y₂Cu₅O₁₀ using resonant inelastic x-ray scattering. By tuning across the Cu L3 edge, we observe abrupt shifts in the dd-peak positions as a function of incident photon energy. This observation demonstrates orbital-specific coupling of the high-energy excited states of the system to the low-energy degrees of freedom. A Franck-Condon treatment of electron-lattice coupling, consistent with other measurements in this compound, reproduces these shifts, explains the Gaussian line shapes, and highlights charge-orbital-lattice renormalization in the high-energy d manifold.