Measurement of linear-response Coulomb drag in insulating a-Si1−xNbx bilayer systems

We report observations of the Coulomb drag effect between insulating a- Si1−xNbx films. We find that a linear-response transresistivity (ρd) can only be realized over a limited range of experimental parameters. We observe an anomalous decrease in the single layer resistance and transresistance at low temperatures (T<3K) due to an additional non-linear response coupling, which is in need of further investigation. In this manuscript, we focus on the behaviour at not too low temperatures (3K