Coulomb drag experiments in low density 2D hole bilayers

We performed experiments studying the Coulomb drag in low density 2D hole bilayers, with r_s ranging from roughly 10 to 20. As the carrier density is lowered into the dilute regime, we observe a significant enhancement of the drag resistivity, such that the interlayer carrier–carrier scattering rate constitutes a major component of the single layer resistivity. In addition, anomalies to the expected temperature and in-plane magnetic field dependences are observed, and are found to correlate with similar anomalies in the single layer resistivity. These results suggests that the origin of the 2D metal–insulator transition phenomena affects both transport properties in a very similar fashion.