Localization in paired correlated random binary alloys.

We study both analytically and numerically the electronic structure and the transport properties of binary chains, when the site energies (e A or e B ) are random in pairs. We compute the density of states and the localization length versus energy for various strengths of disorder by considering products of 2×2 random matrices in the microcanonical ensemble and also within the usual canonical-ensemble method. The limiting cases of AA,BB correlation, which favor delocalization and AB,BA anticorrelation, which favor localization, as well as intermediate cases involving all pairs AA,AB,BA,BB at random, are distinguished