Interaction and disorder in bilayer counterflow transport at filling factor one

We study high mobility, interacting GaAs bilayer hole systems exhibiting counterflow superfluid transport at total filling factor $\nu=1$. As the density of the two layers is reduced, making the bilayer more interacting, the counterflow Hall resistivity ($\rho_{xy}$) decreases at a given temperature, while the counterflow longitudinal resistivity ($\rho_{xx}$), which is much larger than $\rho_{xy}$, hardly depends on density. On the other hand, a small imbalance in the layer densities can result in significant changes in $\rho_{xx}$ at $\nu=1$, while $\rho_{xy}$ remains vanishingly small. Our data suggest that the finite $\rho_{xx}$ at $\nu=1$ is a result of mobile vortices in the superfluid created by the ubiquitous disorder in this system.