SOLITONIC APPROACH TO THE DIMERIZATION PROBLEM IN CORRELATED ONE-DIMENSIONAL SYSTEMS

Using exact diagonalizations, we consider self-consistently the lattic e distortions in odd Peierls-Hubbard and spin-Peierls periodic rings i n the adiabatic harmonic approximation. From the tails of the inherent spin soliton the dimerization d(infinity) of regular even rings is fo und by extrapolations to infinite ring lengths. Considering a wide reg ion of electron-electron on-site interaction values U>0 compared with the band width 4t(0) at intermediately strong electron-phonon interact ion g, known relationships obtained by other methods are reproduced an d/or refined within one unified approach: an example is the maximum of d(infinity) at U similar or equal to 3t(0) for g similar or equal to 0.5 and its shift to zero for g-->g(c) approximate to 0.7. The hyperbo lic tangent shape of the spin soliton is retained for any U and g less than or similar to 0.6. In the spin-Peierls limit the d(infinity) are found to be in agreement with results of density-matrix-renormalizali on-group computations.