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.Comment: 9 pages, cond-mat/yymmnn