Spinons in the strongly correlated copper oxide chains in SrCuO2 -: art. no. 087202

We have investigated the spin dynamics in the strongly correlated chain copper oxide SrCuO2 for energies up to greater than or similar to0.6 eV using inelastic neutron scattering. We observe a gapless continuum of magnetic excitations, which is well described by the Muller ansatz for the two-spinon continuum in the S=1/2 antiferromagnetic Heisenberg spin chain. The lower boundary of the continuum extends up to approximate to360 meV, which corresponds to an exchange constant J=226(12) meV.