Evidence for the influence of electron-electron interaction on the chemical potential of the two-dimensional electron gas

It is shown experimentally that the interaction between electrons strongly influences the chemical potential of the two-dimensional (2D) electron gas. At sufficiently low temperatures and in high magnetic fields, regions of filling factor appear where (i) the chemical potential μ diminishes with increasing carrier density, i.e., the thermodynamic density of states is negative; (ii) the derivative ∂μ/∂H (H is the magnetic field) is considerably higher than the maximum value for a noninteracting 2D electron gas. Using these results, we have estimated that the energy of the e-e interaction in Si inversion layers in a magnetic field is about 1 order of magnitude less than the classical Coulomb interaction calculated for Si metal-oxide-semiconductor field-effect transistors.