For the one-dimensional (1 D) Hubbard model, we extended the bosonization technique, away from half filling, in such a way that a general formula is obtained for the zero temperature equal-time single-particle Green function with validity over the whole doping range. With our method, we can calculate, for the first time, the one-body Green function and thus, the spectral function in both the Tomonaga-Luttinger and Luther-Emery universality classes. The method also gives a tool to determine the coefficients of the correlation functions which cannot be determined with previously used methods.
Recently, there has been considerable interest in the one-dimensional (1D) Hubbard model motivated by various low-dimensional strongly correlated electron systems. In one dimension, Fermi liquid theory breaks down. The effective low-energy theory explicitly exhibits separate elementary excitations carrying charge and spin. Depending on the values of the model parameters, the charge excitation can have two different types oi" behavior, corresponding to either the Tomonaga-Luttinger, or Luther-Emery universality classes. The first behavior, i.e. Tomonaga-Luttinger is characteristic of the lower (metallic) Hubbard band while the Luther-Emery behavior is driven by the upper Hubbard band.
The dispersion relation of the excitations is the same for the _,