Dynamical properties of the 1/r(2)-type supersymmetric t-J model in a magnetic field: Manifestation of spin-charge separation

Quasi-particle picture in a magnetic field is pursued for dynamical spin an d charge correlation functions of the one-dimensional supersymmetric t- J m odel with inverse-square interaction. With use of exact diagonalization and the asymptotic Bethe-ansatz equations for finite systems, excitation conte nts of relevant excited states are identified which are valid in the thermo dynamic limit. The excitation contents are composed of spinons, antispinons , holons and antiholons obeying fractional statistics. Both longitudinal an d transverse components of the dynamical spin structure factor are independ ent of the electron density in the region where only quasiparticles with sp in degrees of freedom (spinons and antispinons) contribute. The dynamical c harge structure factor does not depend on the spin-polarization density in the region where only quasi-particles with charge (holons and antiholons) a re excited. These features indicate the strong spin-charge separation in dy namics, reflecting the high symmetry of the model.