Spin Polarization Dependence of the Coulomb Drag at Large $r_{s}$

We find that the temperature dependence of the drag resistivity ($rho_{D}$) between two dilute two-dimensional hole systems exhibits an unusual dependence upon spin polarization. Near the apparent metal-insulator transition, the temperature dependence of the drag, given by $T^{alpha}$, weakens with the application of a parallel magnetic field ($B_{||}$), with $alpha$ saturating at half its zero field value for $B_{||} > B^{*}$, where $B^{*}$ is the polarization field. Furthermore, we find that $alpha$ is roughly 2 at the parallel field induced metal-insulator transition, and that the temperature dependence of $rho_{D}/T^{2}$ at different $B_{||}$ looks strikingly similar to that found in the single layer resistivity. In contrast, at higher densities, far from the zero field transition, the temperature dependence of the drag is roughly independent of spin polarization, with $alpha$ remaining close to 2, as expected from a simple Fermi liquid picture.