Berlin 2005 – scientific programme

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HL: Halbleiterphysik

HL 4: Quantenpunkte und -dr
ähte: Optische Eigenschaften I

HL 4.10: Talk

Friday, March 4, 2005, 13:00–13:15, TU P-N201

Exciton Dephasing in Quantum Dot Molecules — •Egor Muljarov and Roland Zimmermann — Institut für Physik der Humboldt-Universität zu Berlin, Newtonstr. 15, D-12489 Berlin

A microscopic theory of optical transitions in a multilevel excitonic system with linear coupling to acoustic phonons is developed. The cumulant expansion for the linear and four-wave mixing polarizations is generalized to a multilevel system and allows us to calculate the full time dependence and the spectral lineshape of the polarization. In particular, the broadening of zero-phonon lines is evaluated directly. It is shown that in quantum dot molecules real phonon-assisted transitions between exciton states dominate the dephasing, while virtual transitions are of minor importance. The latter are the only source of dephasing in uncoupled quantum dots [1]. Exciton dephasing rates calculated for a few lowest optical transitions depend strongly on interdot distance (tunnelling), electron-hole Coulomb interaction, and asymmetry of the double-dot potentials.

[1] E. Muljarov and R. Zimmermann, Phys. Rev. Lett. 93, Nov. 2004.