Incoherent transport and pseudo-gap in HoBa2Cu3O7−δ single crystals with different oxygen content

In the present experimental study the temperature dependence of the resistivity, along the c -axis is investigated in HoBa 2 Cu 3 O 7−δ single crystals, with different oxygen contents. It is determined that, the boundaries of the twin domains are effective centers for the scattering of normal carriers. With the reduction of the oxygen content, there is an increase of the processes of the carrier localization. This in turn accompanies the transition from a pseudo-gap regime to the variable-range-hopping regime. For HoBa 2 Cu 3 O 7−δ (in distinction to the YBa 2 Cu 3 O 7−δ , compounds) the temperature dependence for the thermally activated hopping conductivity of the perpendicular resistivity is well described, by the universal “law of ½”.