Interplay of Coulomb blockade and ferroelectricity in nanosized granular materials

We study electron transport properties of composite ferroelectrics--materials consisting of metallic grains embedded in a ferroelectricmatrix. In particular,we calculate the conductivity in a wide range of temperatures and electric fields, showing pronounced hysteretic behavior. In weak fields, electron cotunneling is the main transport mechanism. In this case, we show that the ferroelectric matrix strongly influences the transport properties through two effects: (i) the dependence of the Coulomb gap on the dielectric permittivity of the ferroelectric matrix, which in turn is controlled by temperature and external field, and (ii) the dependence of the tunneling matrix elements on the electric polarization of the ferroelectric matrix, which can be tuned by temperature and applied electric field as well. In the case of strong electric fields, the Coulomb gap is suppressed and only the second mechanism is important.Our results are important for (i) thermometers for precise temperature measurements and (ii) ferrroelectric memristors.