Fractal Nature and Scaling Exponent of Non-Drude Currents in Non-Fermi Liquids

Abstract

In many oxides of the perovskite and pseudoperovskite families there are phase transitions between insulating and normal metallic (Fermi liquid) phases that are separated by an intermediate phase that is often called a non-Fermi liquid (NFL). The dc resistivity of the intermediate or NFL phase often exhibits a T temperature dependence, in contrast to the T2 dependence expected from a bad normal metal. The same alloys exhibit a non-Drude (ND) w2alpha frequency dependence, with alpha ~ 0.5, in contrast to the Drude dependence w2 characteristic of samples with the T2 behavior. Various attempts have been made to modify the algebra of continuum Fermi liquid theory (FLT) to derive the ND exponent alpha, but these have been based on artifices designed to explain only this one parameter. The discrete filamentary model has been used to calculate many properties of high temperature superconductors, and to explain the asymmetric nature of the intermediate phase. Here it is used to derive a by the same rules previously used for several other discrete relaxation calculations that are in excellent agreement with other quite different experiments. The results are: (cubic) perovskites, alpha = 0.45, and planar conductivity of bilayered pseudoperovskites, alpha = 0.70. The corresponding experimental values are (0.4, 0.5) and 0.7.