On the anomalous behaviour at the band centre of a one-dimensional system with off-diagonal disorder

The apparent singularity in the density of states and the non-existence of a limiting distribution of self-energy at the centre of the band in one-dimensional systems with off diagonal disorder, reported by Weissmann and Cohan (see ibid., vol.8, p.L145 (1975)) is related to the existence of a nonlocalized state at that energy. Arguments are given for the extendedness of such a state. Results of Monte Carlo calculations, which confirm these arguments, are discussed.