Low-temperature conduction of a system of tunnel-coupled quantum dots in YBaCuO and LaSrMnO dielectric films

This paper reports on new results of experimental investigations into the nature of the electrical resistivity ρ(T) ? const at T<T _crit for YBaCuO and LaSrMnO dielectric films. The films are prepared by pulsed laser deposition and contain nanocrystalline clusters with metallic conductivity. Dependences of the electrical resistivity ρ(T) ? const are observed for the epitaxial films YBaCuO (T _crit=10 K) with a tetragonal structure after exposure to KrF excimer laser radiation and for the as-prepared amorphous films LaSrMnO (T _crit?160 K). The effect of interest (ρ(T) ? const) manifests itself in the case when the optical spectra of the studied samples contain portions attributed to absorption by free charge carriers. The inference is made that this effect can be associated with tunneling conduction in a system of quantum dots.