Measurement of linear-response Coulomb drag in insulating a- Si 1 − x Nb x bilayer systems

• Published in: Solid state communications Vol. 148; no. 7; pp. 261 - 266
• Main Authors: Elsayad, K., Carini, J.P., Baxter, D.V.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 2008
• Subjects: A. Anderson insulators; A. Silicon–Niobium; D. Coulomb drag; D. Variable range hopping; A. Anderson insulators; 73.20.Fz; 73.61.Jc; A. Silicon–Niobium; D. Coulomb drag; 73.21.Ac; D. Variable range hopping
• ISSN: 0038-1098; 1879-2766
• DOI: 10.1016/j.ssc.2008.09.019

We report observations of the Coulomb drag effect between insulating a- Si 1− x Nb x films. We find that a linear-response transresistivity ( ρ d ) 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 < 3 K ) 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 ( 3 K < T < 15 K ) , where the intralayer transport is unperturbed by the bilayer geometry, and the temperature dependence of ρ d is qualitatively consistent with the layers being Efros–Shklovskii-type (as opposed to Mott-type) Anderson insulators. This is in agreement with past studies on the low energy transport in insulating a- Si 1− x Nb x . We show that functionally the temperature dependence in this regime is consistent with the layers having a 3-d density of states. Comparison to single-layer samples shows that the effective layer thickness is indeed increased in the bilayer geometry.