Van der Waals Theory of the Phase Transition in Quasi-Two-Dimensional Electron Gas in Magnetic Semiconductors

A “liquid—gas” phase transition is investigated in a quasi‐two‐dimensional (quasi‐2D) electron gas in magnetic semiconductors. The quasi‐2D gas is produced by an external electric field in a metal—insulator—semiconductor system. The transition is due to s—f exchange interaction, which gives rise to a strong electron—electron attraction and, under certain conditions, makes the electron gas compression at the surface energetically favorable. The quantitative consideration is based on the analysis of the free energy functional obtained in the effective field approximation. Van der Waals isotherms and the phase diagram of the transition are plotted. The dimensions of electron liquid drops occuring for a given number of quasi‐2D electrons are estimated. Experiments for the detection of the phase transition are suggested. [Russian Text Ignored].