Exact spin dynamics of the 1/r supersymmetric t-J model in a magnetic field

Abstract. The dynamical spin structure factor S(Q, ω) in the small momentum region is derived analytically for the one-dimensional supersymmetric t-J model with 1/r interaction. Strong spin-charge separation is found in the spin dynamics. The structure factor S(Q,ω) with a given spin polarization does not depend on the electron density in the small momentum region. In the thermodynamic limit, only two spinons and one antispinon (magnon) contribute to S(Q,ω). These results are derived via solution of the SU(2,1) Sutherland model in the strong coupling limit.