Abstract
The direction of propagation of acoustic phonons emitted by electron relaxation in weakly confined, parabolic quantum dots charged with one or two electrons is studied theoretically. The emission angle strongly depends on the energy of the phonon, the dominant electron-phonon scattering mechanism (deformation potential or piezoelectric field), and the orbital symmetries of the initial and final electron states. This leads to different behaviors for phonons emitted by electrons relaxing between levels of single and coupled quantum dots. Our results establish the basis to control the direction of propagation of phonon modes triggered by transitions in quantum dot systems.
Highlights
There is currently interest in understanding the physics of electron-acoustic phonon interaction in semiconductor quantum dotsQDs
The direction of propagation of acoustic phonons in parabolic QDs was first studied by Bockelmann,[5] who considered electron-phonon coupling via the deformation potentialDPinteraction, and focused on electron scattering between states of individual QDsintradot transitions
We have investigated the direction of propagation of acoustic phonons due to electron energy relaxation in single and vertically coupled parabolic QDs
Summary
There is currently interest in understanding the physics of electron-acoustic phonon interaction in semiconductor quantum dotsQDs. This is motivated by the fact that acoustic phonons constitute the main source of relaxation between discrete energy levels with few-meV spacing, which is the energy regime where weakly confined QD systems lie.[1,2,3,4] Whereas much theoretical endeavor has been aimed at elucidating how phonon-induced electron-scattering rates depend on the QD geometry and the external fields,[5,6,7,8] very few works have explicitly investigated the orientation of the emitted phonons This is still an interesting problem: on the one hand, there is theoretical evidence that the anisotropy of electron-acoustic-phonon interaction strongly affects the scattering rate;[9,10] on the other hand, QDs may be used to force phonon propagation along a desired direction of the semiconductor lattice.[11]. We show how recently predicted results suggesting the suppression of PZ scattering in two-electron interdot transitions[10] can be related to the direction of phonon emission in CQD systems
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