Tunneling between highly correlated 2D electron systems

Experiments on the tunneling between two parallel 2D electron gases at high magnetic fields are discussed. After reviewing the recent discovery of a broad high field tunneling gap tied to the Fermi level, several new results are presented. These include studies of the detailed shape of the gap near onset and evidence of the fractional quantum Hall effect in the tunneling characteristics. Finally, we present data suggesting that effects of Coulomb interactions on the tunneling may be separable into two distinct regimes.