DO THE EXTENDED STATES IN RANDOM DIMER CHAINS SURVIVE UNDER PERTURBATIONS

We study the delocalization properties of the resonant extended states in the random dimer model (RDM) with various perturbations added. The divergent localization length xi is found to display a power-law deca y xi proportional to W--alpha as a Function of the disorder W in the d imer or the background energies, with an exponent alpha around 2 depen ding on the location of the resonant state. For randomness in the dime r structure the exponent becomes alpha(p) = 1 and for the case of an a pplied electric field it reaches higher values alpha(e) > 2. These eff ects on the resonant states are discussed in connection with the elect ronic transport properties of realistic disordered systems.