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A model of a classical electron liquid without external disorder is applied to two-dimensional electrons in a strong magnetic field. Computer modeling gives a quantitative explanation for the recently observed gap in the tunneling current of a double-quantum-well structure. We find that both the Coulomb gap in the single-well density of states and the correlation of electron motion in the two wells are responsible for the tunneling gap. We showv that the classical liquid model provides an accurate description of the low-temperature compressibility obtained from a magnetocapacitance experiment

A two-dimensional electron liquid (TDEL), subjected to a smooth random potential, is studied in the regime of the fractional quantum Hall effect. An analytical theory of the nonlinear screening is presented for the case when the fractional gap is much less than the magnitude of the unscreened random potential. In this «narrow-gap approximation» (NGA), we calculate the electron density distribution function, the fraction of the TDEL which is in the incompressible state, and the thermodynamic density of states. The magnetocapacitance is calculated to compare with the recent experiments. The NGA is found to be not accurate enough to describe the data. The results for larger fractional gaps are obtained by computer modeling