Quenching of the transmittivity of a one-dimensional binary random dimer model through side-attached atoms

By means of a tight-binding model we study the electronic and transport properties of a one-dimensional system with short-range spatially correlated disorder composed by a periodic chain functionalized by a random distribution of side-attached atoms with enegies EA or EB assigned in pairs as in the random dimer model. The attached atoms are spatially distributed so as to make the original periodic chain a random binary dimer model alloy with energy-dependent on-site parameters. We first consider the case of a single atom and of a couple of atoms, with the same site energy, side-attached to consecutive chain sites. In the case of a couple of attached atoms we evidence significative differences in the local density of states with respect to the case of a single side-attached atom; moreover we find the presence of two transmitting states instead of a single one as it happens in the case of a single substitutional dimer in the chain. We then address the case in which each chain site is decorated by an attached atom as specified above. After a decimation-renormalization procedure we are led to a random binary dimer system with energy-dependent site parameters. We study the localization properties of this system by evaluating the Lyapunov coefficient; we find for it the existence of four delocalized states in the spectrum instead of the two found for embedded random dimers. The Lyapunov coefficient as a function of the electron Fermi energy shows a quite complex behavior with zeros, relative minima, and maxima; their energy positions and heights depend on the site parameters and the coupling interaction of the attached atoms. The analysis of the average transmittivity of finite samples allows us also to show the effects of the competition between the strong localization induced by the presence of the attached atoms and the delocalization of the states due to the short-range order in the distribution of their energy. We show that it is possible to individuate specific parameters of the system to quench the transmittivity of the binary random dimer model.