David Logan

Abstract:

A self-consistent theory of localization in a tight-binding model of topologically disordered systems is investigated. A key element of the theory is use of a disordered reference system in which the structure of the medium is taken into account. The spatial disorder inherent in the Boltzmann center-of-mass distribution is taken as the explicit source of lateral disorder, and the effects of simultaneous site-diagonal disorder are also included. The theory is formulated in a manner which circumvents use of the so-called upper-limit approximation. The Anderson transition density predicted by the theory is estimated for transfer-matrix elements of the forms V(R) R-n, V(R) exp(-R/aH), and V(R) (1+R/aH)exp(-R/aH). Full mobility-edge trajectories for power-law transfer-matrix elements are also determined, with particular emphasis on the cases n=3 and 5 corresponding, respectively, to dipolar and quadrupolar excitons. A connection is also made between the density of states determined from the self-consistent theory and that resultant from solution of the quantum mean spherical integral equation. © 1985 The American Physical Society.

Abstract:

The spectral consequences of the generalised Drude model are examined within the linear hypernetted chain and related theories. A description of collision-induced electronic spectra results, applicable to dense systems. The mechanism involves induced atomic or molecular quadrupoles and stems from the (induced) quadrupole-induced dipole interaction and its many-body analogues. © 1984.

Abstract:

A self-consistent theory of localization of excitations in a tight-binding model of topologically disordered materials such as liquids and gases is proposed. This analysis yields an estimate of the mobility edge for coherent exciton and phonon propagation. Dipolar excitons represent a special case which is commented upon. © 1984 The American Physical Society.