We consider a bilayer electronic system at a total Landau level filling factor $\nu =1\mathrm{}$, and focus on the transition from the regime of weak interlayer coupling to that of the strongly coupled $(1,1,1)$ phase (or “quantum Hall ferromagnet”). Making the assumption that in the transition region the system is made of puddles of the $(1,1,1)$ phase embedded in a bulk of the weakly coupled state, we show that the transition is accompanied by a strong increase in longitudinal Coulomb drag that reaches a maximum of approximately ${h/2e}^2$. In that regime the longitudinal drag increases with decreasing temperature.

• Received 29 November 2001

DOI:https://doi.org/10.1103/PhysRevLett.88.106801