Coulomb Drag in the Extreme Quantum Limit

Coulomb drag resulting from interlayer electron-electron scattering in double layer 2D electron systems in a high magnetic field has been measured. Within the lowest Landau level the observed drag resistance exceeds its zero magnetic value by factors of typically 1000. At half-filling of the lowest Landau level in each layer ( $\nu =1\mathrm{}/2$) the data suggest that our bilayer systems are much more strongly correlated than recent theoretical models based on perturbatively coupled composite fermion metals.