SPECTRAL-ANALYSIS OF CORRELATED ONE-DIMENSIONAL SYSTEMS WITH IMPURITIES

An averaging procedure is proposed to account for spectral features of correlated one-dimensional systems in the presence of nonmagnetic imp urities. The dynamical spin structure factor for a corresponding rando m ensemble of Heisenberg chain segments is calculated by exact numeric al diagonalization. It is shown that a few-mode approximation is suffi cient to describe the numerical results. By examination of the disorde r-induced pseudogap, the loss of spectral weight, and the discrete pea k structures due to smallest-cluster contributions, the underlying imp urity distribution function can be determined.