MAGNETOCONDUCTANCE DUE TO VARIABLE-RANGE-HOPPING IN QUASI-2-DIMENSIONAL SYSTEMS - APPLICATION TO PRBA2CU3O7-DELTA

In this paper, we have developed a theory of magnetoconductance (magne toresistance) due to variable-range hopping for quasi-two-dimensional systems. We have included the effect of electric fields on the calcula tion of the magnetoconductance, The effects of scattering and electron -electron interactions have also been included in our theory. We found analytical expressions for the conductivity for both the scattering a nd nonscattering cases. and obtained electric- and magnetic-field-depe ndent power laws in certain approximations. We found that the electric and magnetic-field dependences of the magnetoconductance had differen t power laws for the scattering and nonscattering cases. We tried to e xplain the van Ancum et al. magnetoconductance experiments of PrBa2Cu3 O7-delta (PBCO) thin films by using our theory. A good agreement betwe en theory and experiment was found if we included the effect of scatte ring. In the above PBCO films, it was found that the approximate value of the concentration of localized states lies between 10(11) and 10(1 2) cm(-2).