CONTINUOUS METAL-NONMETAL TRANSITION IN DISORDERED MATERIALS.

The existence is proposed of an inhomogeneous transport regime in disordered materials in which gradual metal-semiconductor transition occurs. The material may be viewed as consisting of a random microscopic mixture of metallic and semiconducting regions, the density of states is reduced by the allowed (metallic) volume fraction, C(E//F), at the Fermi energy. The inhomogeneous regime is subdivided into pseudometallic and pseudosemiconductor parts separated by a percolation threshold. An effective-medium theory for the conductivity and for the Hall effect was applied to handle several classes of materials undergoing metal-nonmetal transition via the inhomogeneous transport regime.