Small-polaron variable-range hopping in quasi-twodimensional materials: application to PrBa2Cu3-xGaxO7-y

Abstract

We have developed a theory for variable-range hopping (VRH) due to small polarons in quasi-two-dimensional systems at high temperatures. We included the e ects of temperature, electric ® elds, magnetic ® elds and scattering in the derivation of the conductivity. We found that the conductivity for quasi-twodimensional systems depends on these factors di erently from threedimensional systems. We applied the theory to explain the resistivity data of PrBa 2 Cu 3 x Ga x O 7 y at high temperatures T > 150 K . To explain the lowtemperature data T < 150 K , we used the pure electron VRH mechanisms.Good agreement between theory and experiment was found.