Pairing correlations in the incoherent phase of quantum Hall bilayers?*

At sufficiently small layer separation, Coulomb interactions in bilayer 2D electron systems at high magnetic field can stabilize an excitonic phase in which electrons in one layer are bound to holes in the other. The excitonic phase is macroscopically phase coherent, exhibiting numerous remarkable transport properties analogous to those of superconductivity and superfluidity. While the excitonic phase is theoretically relatively well understood, the incoherent phase at layer separations slightly larger than the critical one is not. In this talk we will discuss recent transport and interlayer tunneling spectroscopy measurements which demonstrate the importance of interlayer Coulomb interactions in the incoherent phase. In addition to screening of the Coulombic repulsion between electrons in the same layer, our measurements suggest that interlayer electron-hole pairing correlations may persist into the incoherent phase at intermediate layer separations.