Microwave-Enhanced hopping-conductivity; a non-Ohmic Effect

TL;DR

This paper demonstrates that microwave fields can significantly enhance hopping conductivity in Anderson-localized systems, suggesting a high-frequency non-Ohmic effect that challenges existing models and explains low threshold fields.

Contribution

It introduces the concept of microwave-enhanced hopping conductivity as a high-frequency non-Ohmic effect, supported by experimental data across various systems.

Findings

Microwave fields increase hopping conductivity in localized systems.

The effect is consistent across different Anderson-localized materials.

Existing models cannot fully explain the low threshold fields observed.

Abstract

Hopping conductivity is enhanced when exposed to microwave fields (Phys. Rev. Lett., 102, 206601, 2009). Data taken on a variety of Anderson-localized systems are presented to illustrate the generality of the phenomenon. Specific features of these results lead us to conjecture that the effect is due to a field-enhanced hopping, which is the high frequency version of the non-Ohmic effect, well known in the dc transport regime. Experimental evidence in support of this scenario is presented and discussed. It is pointed out that existing models for non-Ohmic behavior in the hopping regime may, at best, offer a qualitative explanation to experiments. In particular, they cannot account for the extremely low values of the threshold fields that mark the onset of non-Ohmic behavior.