Spin-charge separation probed with resonant inelastic x-ray scattering on doped one-dimensional antiferromagnets

We propose a new method to observe spin-charge separation and other exotic excitations in doped Sr₂CuO₃ using the resonant inelastic x-ray scattering (RIXS) technique, which can simultaneously probe charge and spin degrees of freedom. Sr₂CuO₃ hosts corner-shared CuO₃ plaquettes, in which the Cu spin moment-1/2 couples antiferromagnetically along a one-dimensional (1D) chain. Importantly, the spin-chain can be doped with Co, Ni or Zn. We model the spin-chain by exactly diagonalizing the 1D t-J Hamiltonian to study low energy spin and charge excitations of the doped system and provide predictions of the RIXS spectra at the oxygen K-edge for doped Sr2CuO3. Our results show that the RIXS spectra are rich, containing distinct two- and four-spinon excitations, dispersive antiholon excitations, and combinations thereof. We also study dynamical spin and charge structure factors using DMRG which complements the RIXS spectra and helps to identify the spin and charge excitations.