Scaling behavior at the insulator-metal transition in Bi2Sr2(CazR1-z)Cu2O8+y where R is a rare-earth element.

We report on the details of the insulator-metal transition (IMT) induced in Bi 2 Sr 2 (Ca z ,R 1-z )Cu 2 O 8+y (R=Y, Gd, Nd) by Ca 2+ doping. The resistivity in the insulating regime is analyzed using a generalized hopping approach based on the connectivity criterion. This enables us to estimate the dependence of the localization radius a H on the Ca concentration independent of dimensionality