Population Inversion and Coherent Phonon Emission in a Biased Quantum Dot System Placed in an Acoustic Cavity

Abstract

We have analyzed electron dynamics in a semiconductor double‐dot system attached to leads. The voltage bias applied to this structure gives rise to electron localization in the constituent dots. We have solved the Schrodinger equation numerically to determine the overlap integrals of the double‐dot electron wave functions and the wave functions of the leads, and, accordingly, to obtain the ratios of the tunnel coupling constants in the microscopic basis. The populations of the double‐dot electron levels have been found from the nonequilibrium Green’s function technique. We have shown that for the appropriate bias voltage there is population inversion between the upper electron level mainly connected to the lead with higher chemical potential and the lower electron level effectively emptied to the lead with lower chemical potential. When such a system is suspended and forms an acoustic cavity having specific phonon modes, the electron‐phonon interaction becomes resonant and can lead to coherent phonon generation.