Low temperature electrical resistivity in systems with lattice instabilities

I present a model which focuses on the role of polarons in systems with tunneling states represented by double well potentials. The underlying hypothesis is the presence of local lattice instabilities associated with the high polarizability of, for instance, oxygen ions in the high T c superconductors [1] or, vanadium atoms in the A15 compounds. The time retarded interactions between two level systems and tightly bound electrons can lead to the trapping of the charge carriers at low temperatures. The low temperature negative dρ/dT observed in systems with structural instabilities is accounted for by the present model.