Tunneling between two-dimensional electron gases in a strong magnetic field.

We have measured the tunneling between two two-dimensional electron gases at high magnetic fields B, when the carrier densities of the two electron layers are matched. For filling factors ν < 1, there is a gap in the current-voltage characteristics centered about V = 0, followed by a tunneling peak at ∼ 6 mV. Both features have been observed before and have been attributed to electron-electron interactions within a layer. We have measured high field tunneling peak positions and fitted gap parameters that are proportional to B, and independent of the carrier densities of the two layers. This suggests a different origin for the gap to that proposed by current theories, which predict a √ B dependence.