Effects of disorder on collective modes in single-and double-layer Bose systems

Abstract

We report some new results from our study of two-dimensional (2D) Bose systems, particularly the collective excitations in 2D charged Bose gas, in the presence of disorder. The effects of disorder are taken into account through collisions the Bose particles suffer due to disorder; these collisions are considered in the relaxation-time approximation within a number-conserving scheme in the random-phase approximation (RPA) at T = 0. The dependence of the plasmon dispersion on the boson interparticle potential, and the critical wave vector below which the plasma excitations cannot propagate, are investigated. The static structure factor S(q) in the presence of disorder is evaluated in closed form. We consider single- and double-layer systems and compare our results with the corresponding electron gas systems. A double-layer system in which one layer is disordered while the other is disorder-free exhibits results analogous to the 'drag effect'. Many-body extensions beyond the RPA are also discussed.