SINGLE-ELECTRON TUNNELING INTO RANDOMLY DISTRIBUTED DOUBLE-ELECTRON STATES - LINEAR VOLTAGE AND TEMPERATURE DEPENDENCES OF THE CONDUCTANCE OF HIGH-T(C) TUNNEL-JUNCTIONS

In sandwich-type tunnel junctions of high-T(c) materials the conductance is observed to have a large zero-bias value, linear voltage dependence at low temperature, and linear temperature dependence at low voltage. We suggest a model of single-electron tunneling into randomly distributed (disordered) local centers with strong interelectron attraction to explain these features. In point-contact tunnel junctions these features should be absent due to local homogeneity in contacts of small area. We compare predictions of the model with experiment.