Dynamical symmetry enlargement versus spin-charge decoupling in the one-dimensional SU(4) Hubbard model

We investigate dynamical symmetry enlargement in the half-filled SU(4) Hubbard chain using nonperturbative renormalization-group and quantum Monte Carlo techniques. A spectral gap is shown to open for arbitrary Coulombic repulsion U. At weak coupling, Uless than or similar to3t, a SO(8) symmetry between charge and spin-orbital excitations is found to be dynamically enlarged at low energy whereas at strong coupling, Ugreater than or similar to6t, the charge degrees of freedom dynamically decouple. The crossover between these regimes is discussed.