## Self-consistent three-pole approximation study of the spin dynamics in two-dimensional antiferromagnetic Heisenberg paramagnets

The dynamics of spin-1/2 two-dimensional quantum Heisenberg antiferromagnets are reexamined in the framework of a self-consistent correlation theory based on the three-pole approximation of the relaxation function. The self-consistency is imposed between the static and dynamic variables, which dramatically changes the picture of the spin dynamics by broadening the quantum critical (QC) region (0.2{ital J}{lt}{ital T}{lt}{ital J}) and narrowing the renormalized classical (RC) region ({ital T}{lt}0.1{ital J}), resulting in a small spin stiffness as required by other theories. As an application of the theory, the calculated nuclear relaxation rates of 1/{ital T}{sub 1} and 1/{ital T}{sub 2{ital G}} in La{submore »