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-squ are interaction in a magnetic field. With use of exact diagonalization and the asymptotic Bethe-ansatz equations for finite systems, excitation conten ts of intermediate states are identified in the thermodynamic limit. The dy namical charge structure factor is independent of the spin-polarization den sity in the region where only quasi-particles with charge (holons and antih olons) are excited. The spin dynamics do nor depend on the electron density in the region where only quasi-particles with spin degrees of freedom (spi nons and antispinons) contribute. These features indicate the strong spin-c harge separation in dynamics, reflecting the high symmetry of the model. (C ) 2000 Elsevier Science B.V. All rights reserved.