Coulomb drag and tunneling studies in quantum Hall bilayers

<p>The bilayer quantum Hall state at total filling factor <i>ν_T=1</i>, where the total electron density matches the degeneracy of the lowest Landau level, is a prominent example of Bose-Einstein condensation of excitons. A macroscopically ordered state is realized where an electron in one layer is tightly bound to a "hole" in the other layer. If exciton transport were the only bulk transportmechanism, a current driven in one layer would spontaneously generate a current of equal magnitude and opposite sign in the other layer. The Corbino Coulomb drag measurements presented in this thesis demonstrate precisely this phenomenon.</p> <p>Excitonic superfluidity has been long sought in the <i>ν_T=1</i> state. The tunneling between the two electron gas layers exihibit a <i>dc</i> Josephson-like effect. A simple model of an overdamped voltage biased Josephson junction is in reasonable agreement with the observed tunneling <i>I-V</i>. At small tunneling biases, it exhibits a tunneling "supercurrent". The dissipation is carefully studied in this tunneling "supercurrent" and found to remain small but finite.</p>