Understanding the dynamics of atomic vibrations confined in quasi-zero dimensional systems is crucial from both a fundamental point-of-view and a technological perspective. Using ultrafast electron diffraction, we monitored the lattice dynamics of GaAs quantum dotsâgrown by Droplet Epitaxy on AlGaAsâwith sub-picosecond and sub-picometer resolutions. An ultrafast laser pulse nearly resonantly excites a confined exciton, which efficiently couples to high-energy acoustic phonons through the deformation potential mechanism. The transient behavior of the measured diffraction pattern reveals the nonequilibrium phonon dynamics both within the dots and in the region surrounding them. The experimental results are interpreted within the theoretical framework of a non-Markovian decoherence, according to which the optical excitation creates a localized polaron within the dot and a travelling phonon wavepacket that leaves the dot at the speed of sound. These findings indicate that integration of a phononic emitter in opto-electronic devices based on quantum dots for controlled communication processes can be fundamentally feasible. © 2017 Author(s).
Vanacore, G., Jianbo, H., Liang, W., Bietti, S., Sanguinetti, S., Carbone, F., et al. (2017). Ultrafast atomic-scale visualization of acoustic phonons generated by optically excited quantum dots. STRUCTURAL DYNAMICS, 4(4), 044034 [10.1063/1.4998009].
Ultrafast atomic-scale visualization of acoustic phonons generated by optically excited quantum dots
Giovanni M. , Vanacore;Bietti, Sergio;Sanguinetti, Stefano;
2017
Abstract
Understanding the dynamics of atomic vibrations confined in quasi-zero dimensional systems is crucial from both a fundamental point-of-view and a technological perspective. Using ultrafast electron diffraction, we monitored the lattice dynamics of GaAs quantum dotsâgrown by Droplet Epitaxy on AlGaAsâwith sub-picosecond and sub-picometer resolutions. An ultrafast laser pulse nearly resonantly excites a confined exciton, which efficiently couples to high-energy acoustic phonons through the deformation potential mechanism. The transient behavior of the measured diffraction pattern reveals the nonequilibrium phonon dynamics both within the dots and in the region surrounding them. The experimental results are interpreted within the theoretical framework of a non-Markovian decoherence, according to which the optical excitation creates a localized polaron within the dot and a travelling phonon wavepacket that leaves the dot at the speed of sound. These findings indicate that integration of a phononic emitter in opto-electronic devices based on quantum dots for controlled communication processes can be fundamentally feasible. © 2017 Author(s).File | Dimensione | Formato | |
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