Quantum dynamics of charged and neutral magnetic solitons: Spin-charge separation in the one-dimensional Hubbard model

We demonstrate that the configuration interaction (CI) approximation recapt ures essential features of the exact (Bethe-ansatz) solution to the one-dim ensional (1D) Hubbard model. As such, it provides a valuable route for desc ribing effects that go beyond mean-field theory for strongly correlated ele ctron systems in higher dimensions. The CI method systematically describes fluctuation and quantum tunneling corrections to the Hartree-Fock approxima tion (HFA). HFA predicts that doping a half-filled Hubbard chain leads to t he appearance of charged spin polarons or charged domain-wall solitons in t he antiferromagnetic background. The CI method, on the other hand, describe s the quantum dynamics of these: charged magnetic solitons and quantum tunn eling effects between various mean-field configurations. In this paper, we test the accuracy of the CI method against the exact solution of the one-di mensional Hubbard model. We find remarkable agreement between the energy of the mobile charged bosonic domain wall (a!; given by the CI method) and th e exact energy of the doping hole (as given by the Bethe ansatz) for the en tire U/t range. The CI method also leads to a clear demonstration of the sp in-charge separation in one dimension. Addition of one doping hole to the h alf-filled antiferromagnetic chain results in the appearance of two differe nt carriers. a charged bosonic domain wall (which carries the charge but no spin) and a neutral spin-1/2 domain wall (which carries the spin but no ch arge).