A $$\hbox {j}_{\mathrm{eff}} = 1/2$$jeff=1/2 pseudospinon continuum in $$\hbox {CaIrO}_{{3}}$$CaIrO3

In so-called $$j_\mathrm {eff} = 1/2$$  systems, including some iridates and ruthenates, the coherent superposition of $$t_\mathrm {2g}$$ orbitals in the ground state gives rise to hopping processes that strongly depend on the bond geometry. Resonant inelastic X-ray scattering measurements on CaIrO $$_3$$ reveal a prototypical $$j_\mathrm {eff} = 1/2$$  pseudospinon continuum, a hallmark of one-dimensional (1D) magnetic systems despite its three-dimensional crystal structure. The experimental spectra compare very well to the calculated magnetic dynamical structure factor of weakly coupled spin-1/2 chains. We attribute the onset of such quasi-1D magnetism to the fundamental difference in the magnetic interactions between the $$j_\mathrm {eff} = 1/2$$  pseudospins along the corner- and edge-sharing bonds in CaIrO $$_3$$ .