Frictional drag between two dilute two-dimensional hole layers

We report drag measurements on dilute double layer two-dimensional hole systems in the regime of r(s)=19-39 . We observed a strong enhancement of the drag over the simple Boltzmann calculations of Coulomb interaction, and deviations from the T-2 dependence which cannot be explained by phonon-mediated, plasmon-enhanced, or disorder-related processes. We suggest that this deviation results from interaction effects in the dilute regime.