One-dimensional Frenkel exciton systems near the band center with off-diagonal correlated and uncorrelated disorder

A study is carried out for one-dimensional Frenkel excitons near the band c enter in a system with nearest-neighbor off-diagonal random interactions. T he uncorrelated and the correlated (positional disorder) cases are consider ed for chains of 10(7) atoms. The low-energy spectrum and its localization properties are investigated through the integrated density of states and th e inverse localization length. We have tested the predictions of the scalin g theory developed for the uncorrelated case against our numerical data and found good agreement as the energy approaches the band center. We have als o established that the correlated case, with a general, realistic random in teraction also shows scaling behavior with an amplitude constant that is tw ice as large as in the uncorrelated case. [S0163-1829(99)04630-5].