SYSTEMATIC NUMERICAL STUDY OF SPIN-CHARGE SEPARATION IN ONE-DIMENSION

The problem of spin-charge separation is analyzed numerically in the m etallic phase of the one-band Hubbard model in one dimension by studyi ng the behavior of the single-particle Green's function and of the spi n and charge susceptibilities. We first analyze the quantum Monte Carl o data for the imaginary-time Green's function within the maximum-entr opy method in order to obtain the spectral function at real frequencie s. For some values of the momentum sufficiently away from the: Fermi s urface two separate peaks are found, which can be identified as charge and spin excitations, In order to improve our accuracy and to be able to extend our study to a larger portion of the Brillouin zone, me als o fit our data with the imaginary-time Green's function obtained from the Luttinger-model solution with two different velocities as fitting parameters. The excitation energies associated with these velocities t urn out to agree, in a broad range of momenta, with the ones calculate d from the charge and spin susceptibilities. This allows us to identif y these single-particle excitations as due to a separation of spin and charge. Remarkably, the range of momenta where spin-charge separation is seen extends well beyond the region of linear dispersion about the Fermi surface. We finally discuss a possible extension of our method to detect spin-charge separation numerically in two dimensions.