THE EFFECT OF ELECTRON-ELECTRON INTERACTION ON THE ELECTRIC-FIELD DEPENDENT VARIABLE-RANGE-HOPPING CONDUCTION IN QUASI-LOW-DIMENSIONAL SYSTEMS

We have calculated the variable range hopping conductivity of quasi-on e-, quasi-two-, and anisotro-pic quasi-two-dimensional systems in the presence of an electric field. We considered the effect of electron-el ectron interaction through the density of states in the variable range hopping mechanism. In the presence of the electron-electron interacti on, the density of stales is proportional to the energy of the localiz ed elections. Using this density of states, the expressions of the con ductivity are calculated by using the method developed by the authors. At zero electric field, our results of the temperature dependence of conductivity reduce to that given in the literature. We found that for beta much greater than 1, the logarithm of conductivity is proportion al to beta(-1/2) for quasi-one and quasi-two-dimensional systems and t o beta(-2/3) for anisotropic quasi-two-dimensional systems. Here beta is proportional to the electric field and inversely proportional to th e temperature. Recent electric field dependent coil experiments on low -dimensional B14T11S10 compounds predict a beta(-2/3) power law at hig h electric fields. Hence our theory of anisotropic quasi-two-dimension al systems is consistent with these experiments. We have also compared our theory with an entire range of electric field dependent conductiv ity data of Bi14Te11S10 compounds. A good agreement between theory and experiment has also been found on a qualitative basis.