APPROXIMATE DECOUPLING OF SPIN AND CHARGE EXCITATIONS IN THE 2-DIMENSIONAL T-J MODEL

The single-particle spectral functions for the two-dimensional t-J mod el are investigated in connection with spin and charge dynamics, using the exact diagonalization technique. At low electron density, Fermi l iquid behavior is observed. Near half-filling, the spectral functions reveal a two-peak structure which is due to the different dynamics of spin and charge degrees of freedom. This density dependence of the spe ctral functions indicates a crossover from Fermi liquid behavior at lo w density to anomalous behavior near the Mott transition where the app roximate decoupling of spin and charge excitations occurs.