Resonant Inelastic X-Ray Scattering of the Holon-Antiholon Continuum in SrCuO~2

We report a resonant inelastic x-ray scattering study of charge excitations in the quasi-one-dimensional Mott insulator SrCuO 2 . We observe a continuum of low-energy excitations, the onset of which exhibits a small dispersion of ∼0.4 eV. Within this continuum, a highly dispersive feature with a large sinusoidal dispersion (∼ 1.1 eV) is observed. We have also measured the optical conductivity, and studied the dynamic response of the extended Hubbard model with realistic parameters, using a dynamical density-matrix renormalization group method. In contrast to earlier work, we do not find a long-lived exciton, but rather these results suggest that the excitation spectrum comprises a holon-antiholon continuum together with a broad resonance.