Variable Range Hopping Conductivity: Case of the non-constant density of states

The variable range hopping theory has been widely used these last years to explain the electric conduction process in some biological systems as DNA. However, the experimental measurements on such systems reveal that the density of states varies strongly near Fermi level. This observation suggests that the theoretical concept of "constant density of states" near Fermi level is certainly insufficient to justify the observation of the T conductivity in such systems. To overcome this difficulty, we show in this work that this conductivity may be obtained for any odd number q when the density of states is expressed under the asymmetric power law form: N(E) = N(EF) + const E. For this density of states, the thermoelectric power is also investigated.