Vanishing hall resistance at high magnetic field in a double-layer two-dimensional electron system

The measurement of the Hall and longitudinal resistance of a double layer 2DES in a strong perpendicular magnetic field B was discussed. At total Landau Level filling factor ν_tot=1 a double layer two dimensional electron system with small interlayer separation supports a collective state prossessing spontaneous interlayer phase coherence. It was observed that longitudinal and Hall resistance of each layers vanish in the low temperature if the currents in two layers are equal but oppositely directed. This supports the prediction that the ground state at ν_tot=1 was an excitonic superfluid.