DENSITY-OF-STATES AND LOCALIZATION LENGTH IN WEAKLY DISORDERED PEIERLS CHAINS

The electron density of states and localization length are calculated for weakly disordered dimerized tight-binding chains. Pure bond disord er causes a singular density of states for small bond gaps, and a sing ular localization length for zero bond gap, whereas larger bond gaps a re transformed into pseudogaps. A site gap for diatomic chains is pres erved under bond disorder. Site disorder destroys any gap and does not create singularities in the density of states or localization length. These results are compared with those obtained from the continuum app roximation with Gaussian disorder, which is not strictly justified for short-ranged disorder potentials. However, the continuum results are valid for weakly disordered chains provided the bond and site disorder s in the chain correspond to bond-gap and combined site and site-gap d isorders in the continuum model, respectively.