Dynamics of the t-J model in a magnetic field

Quasi-particle picture is pursued for dynamical charge and spin correlation functions of the one-dimensional supersymmetric t-J model with inverse-square interaction in a magnetic field. With use of exact diagonalization and the asymptotic Bethe-ansatz equations for finite systems, excitation contents of intermediate states are identified in the thermodynamic limit. The dynamical charge structure factor is independent of the spin-polarization density in the region where only quasi-particles with charge (holons and antiholons) are excited. The spin dynamics do not depend on the electron density in the region where only quasi-particles with spin degrees of freedom (spinons and antispinons) contribute. These features indicate the strong spin-charge separation in dynamics, reflecting the high symmetry of the model.