Browsing by Author "Hawrylak, P."

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Controlling magnetism of semi-magnetic quantum dots with odd-even exciton numbers
(2008)
Cheng, S. -J.
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Hawrylak, P.
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電子物理學系
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Department of Electrophysics
We present a theory of optical control of magnetism in a self-assembled quantum dot ( SAD) containing magnetic ions. We show that the magnetic state of Mn ions can be controlled by the number of excitons in the dot. For an odd number of excitons the magnetic ions are coupled by the spins of valence holes and electrons. For an even number of excitons we derive the effective RKKY interaction between Mn ions, and show that it is controlled by valence holes. We predict the emission spectra of the coupled Mn-exciton system and relate them to the magnetic state of ions and the number of excitons in the quantum dot. Copyright (C) EPLA, 2008.
Single-exciton energy shell structure in InAs/GaAs quantum dots
(2008-12-01)
Awirothananon, S.
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Raymond, S.
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Studenikin, S.
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Vachon, M.
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Render, W.
The energy shell structure of a single exciton confined in a self-assembled quantum dot (QD), including excited states, is studied in a regime where the direct Coulomb attraction energy is comparable to the kinetic energy of the carriers. This is achieved via magnetophotoluminescence excitation spectroscopy experiments, where a magnetic field applied perpendicular to the plane of the QD is used to reveal the angular-momentum content of energy shells. The absorption spectrum of the QDs is modeled, and comparison with experiment allows us to relate the observed transitions to interband QD bound-state transitions. The blueshift of the absorption peaks compared to the emission peaks is then interpreted in terms of many-body interactions, and we show that for a highly symmetric situation, the observed energy difference gives a direct measurement of the extra exchange energy gained upon addition of an extra exciton in the QD.