Electron-electron interactions in the two-dimensional electron gas in silicon

We have measured the magnetocapacitance of silicon metal-oxide-semiconductor field-effect transistors in the high-field extreme quantum limit, where only the lowest Landau level is partially occupied and the thermodynamic density of states of two-dimensional electrons is negative. A satisfactory agreement between the measured and calculated density of states has been observed. This indicates that the energy of electron-electron interactions in this system is close to the calculated value, in contrast to previous reports.