QUANTUM FLUCTUATIONS TO DESTROY THE ANTIFERROMAGNETIC SPIN ORDER IN THE ONE-DIMENSIONAL HALF-FILLED HUBBARD-MODEL

Quantum fluctuations in the one dimensional half filled Hubbard model are investigated with the resonating Hartree-Fock method with the orbi tal optimization. The optimized Slater determinants include an inhomog eneous spin density wave and configurations accommodating some neutral soliton pairs. The short and long range spin orders are destroyed by quantum translational and breathing motions of soliton pairs and gaple ss Gaussian type fluctuations, respectively. Our calculation suggests that the lowest singlet and triplet excitation branches are the transl ational modes of breathing neutral soliton pairs dressed with the Gaus sian type fluctuations.