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Abstract

Many-component electron-hole plasma is considered in the coupled quantum wells. The electrons are assumed to be localized in one quantum well (QW) while the holes are localized in the other QW. It is found that the homogeneous charge distribution within the QWs is unstable if the carrier density is sufficiently small. The instability results in the breakdown of the homogeneous charge distribution into two coexisting phases-a low-density phase and a high-density phase, which is electron-hole liquid. In turn, the homogeneous state of the electron-hole liquid is stable if the distance between the quantum wells l is sufficiently small. However, as the distance l increases and reaches a certain critical value l(cr), the plasmon spectrum of the electron-hole liquid becomes unstable. Hereupon, a quantum phase transition occurs, resulting in the appearance of charge-density waves of finite amplitude in both quantum wells. Strong mass renormalization and the strong Z-factor renormalization are found for the electron-hole liquid as the quantum phase transition occurs.