On the continuum 'spin-wave' spectrum of the one-dimensional Hubbard model

The authors re-examine the triplet (S=1) 'spin-wave' excitations of the exactly solvable spin- 1 / 2 1D Hubbard chain. They indicate that a continuous spectrum exists for all couplings U. In the strong coupling U to infinity limit, the spin-wave continuum spectrum of the isotropic Heisenberg antiferromagnet is recovered, for the half-filled band. Results for the quarter-filled band are also obtained by numerical solution of a set of linear integral equations. In addition they compare the particle-hole spectrum obtained by Coll (1974) with the Stoner excitations for a spiral spin density wave Hartree-Fock theory and found good qualitative agreement.