FREQUENCY-DEPENDENT SPIN SUSCEPTIBILITY IN THE 2-DIMENSIONAL HUBBARD-MODEL

A quantum Monte Carlo calculation of the dynamical spin susceptibility in the half-filled 2D Hubbard model is presented for temperature T = 0.2t and an intermediate on-site repulsion U = 4t. Using the singular- value decomposition technique we succeed in analytically continuing th e Matsubara Green's function into the real-frequency domain and in der iving the spectral representation for longitudinal and transverse spin susceptibility. The simulation results, while contradicting the rando m-phase approximation prediction of antiferromagnetic long-range order at this temperature, are in agreement with an extension of the self-c onsistent renormalization approach of Moriya. The static susceptibilit y calculated using this technique is qualitatively consistent with the omega --> 0 simulation results.