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Fluctuation properties of phonons generated by ultrafast optical excitation of a quantum dot
Author(s) -
Reiter D. E.,
Wigger D.,
Daniels J. M.,
Papenkort T.,
Vagov A.,
Axt V. M.,
Kuhn T.
Publication year - 2011
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.201000783
Subject(s) - phonon , excitation , superposition principle , physics , ultrashort pulse , exciton , pulse (music) , coherent states , wigner distribution function , raman spectroscopy , condensed matter physics , ground state , quantum dot , quantum fluctuation , laser , quantum , atomic physics , quantum mechanics , voltage
In this paper, the fluctuation properties of phonons after the optical excitation of a quantum dot with an ultrashort laser pulse are studied theoretically. When a single pulse with pulse area π creates an exciton in the system, a coherent phonon state builds up. Fluctuations of coherent states are time independent and equal to the vacuum fluctuations. By an excitation with a π /2 pulse a superposition of ground and exciton state is created. In this case the phonon system becomes entangled with the electronic system. In the phonon subsystem this leads to the formation of a statistical mixture of the vacuum and the coherent state. The fluctuations of this mixture oscillate in time with both the single and the double phonon frequency, but never exhibit squeezing. The discrepancies with the predictions made in a Raman tensor model are briefly discussed. All scenarios are illustrated using the Wigner function.