Two-dimensional electron-hole metallic liquids

Abstract

The ground state energy of two-dimensional electron-hole liquids is calculated in the generalized random phase approximation. It is shown that the cohesive energy per electron-hole pair exceeds the binding energy of a two-dimensional exciton in the case of a system with two conduction band minima and a single valence band maximum with a heavier effective mass. A possibility of producing electron-hole “pancakes” in layer-type semiconductors is pointed out. The many-body correction of the effective masses and dispersion relations of collective modes are also derived. Finally the condition for occurrence of excitonic phases is discussed.