DISTRIBUTION OF THE DENSITY OF LOCALIZED STATES IN DISORDERED-SYSTEMS

There is performed a calculation of the density of localized states, involving the preexponential factor for the 3D diagonal disorder single-band hamiltonian. A new element in the approach to the problem is an additional restriction of the class or functions minimizing the action functional in the single-instanton approximation. The results of analyzing the problem on localized states in the concrete realizations of the disordered system concerned serve as a background for an additional restriction. The problem on strong scattering in the limit of the small concentration or scattering centers is analyzed. The situation is studied in the ternary system composed of binary solid solution where each site is a weak scatterer and deep impurities centers serve as a third component, the concentration of centers being assumed to be small. In all the cases the general as well as simplified expressions for the preexponential factors are found. It is shown that in the limiting cases the solution obtained coincides with the exact solution of problem. A comparison is performed of experimental Si with the calculation results, demonstrating a good agreement with the theory.