  Magneto-transport and drag measurements on a quasi-Corbino 2D electron
bilayer at the systems total filling factor 1 (v_tot=1) reveal a drag voltage
that is equal in magnitude to the drive voltage as soon as the two layers begin
to form the expected v_tot=1 exciton condensate. The identity of both voltages
remains present even at elevated temperatures of 0.25 K. The conductance in the
current carrying layer vanishes only in the limit of strong coupling between
the two layers and at T->0 K which suggests the presence of an excitonic
circular current.
