Browsing by Author "Cheng, S. -J."

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Anisotropic nature of hole g-factor in individual InAs quantum rings
(2017-02-01)
Kaji, R.
;
Tominaga, T.
;
Wu, Y. -N.
;
Wu, M. -F.
;
Cheng, S. -J.
The in-plane g-factors of electron and hole spins (g perpendicular to e, g perpendicular to h) confined in the individual InAs/GaAs quantum rings (QRs) were investigated by using experimental and theoretical approaches. From the measurements, we found that the experimentally obtained \g perpendicular to h\varies largely from QR to QR, while the variation in \g perpendicular to e\ is small. In addition, the in-plane (x-y) and the out-of-plane (x-z) anisotropies in hole g-factor were obviously confirmed while the electron g-factor exhibits isotropic natures in both cases. From the model calculations, the effects of the shape anisotropies and the uniaxial stress were examined. The shape anisotropy in QRs modifies the spatial distributions of hole wavefunctions. Thus, it brings the resultant changes in the degree of valence-band mixing and \g perpendicular to h\, and combined with uniaxial stress, a larger modulation in \g perpendicular to h\ was achieved. Although more detailed discussions are necessary at this stage, our findings will give valuable information for the g-factor control in semiconductor nanostructures.
Controlling magnetism of semi-magnetic quantum dots with odd-even exciton numbers
(2008)
Cheng, S. -J.
;
Hawrylak, P.
;
電子物理學系
;
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.
Electron and hole in-plane g-factors in single In As quantum rings
(2015-01-01)
Kaji, R.
;
Tominaga, T.
;
Wu, Y. -N.
;
Cheng, S. -J.
;
Adachi, S.
The electron and hole in-plane g-factors were studied in individual InAs/GaAs quantum rings (QRs). From the magneto-photoluminescence measurements under a transverse magnetic field, we evaluated the in-plane g-factors of electron and hole spins by rotating the sample systematically along the crystal growth axis. The experimental results indicate that the in-plane and the out-of-plane anisotropies in hole g-factor are larger than those of electron g-factor, and the value of the hole in-plane g-factor varies largely from QR to QR while the electron g-factor is almost a constant value. From the model calculation considering the effects of shape anisotropies and uniaxial stress, we examined the correlation between the in-plane g-factors and the degree of valence band mixing. Further, the experimentally obtained trend in g-factors was in agreement qualitatively with theoretical consideration.
Hole g-Factor Anisotropies in Individual InAs Quantum Rings
(2016)
Kaji, R.
;
Tominaga, T.
;
Wu, Y. -N.
;
Wu, M. -F.
;
Cheng, S. -J.
We investigated the electron and hole g-factors in individual InAs/GaAs quantum rings (QRs). From the magneto-photoluminescence measurements under a transverse magnetic field, we evaluated the in-plane g-factors of electron and hole spins by rotating the sample systematically around the crystal growth axis. The experimental results indicate that the in-plane and the out-of-plane anisotropies in hole g-factor are larger than those of electron g-factor, and the value of the hole in-plane g-factor varies largely from QR to QR while the electron g-factor is almost a constant value. From the model calculation considering the effects of shape anisotropies and uniaxial stress, we examined the correlation between the in-plane g-factors and the degree of valence band mixing. Further, the experimentally obtained trend in g-factors was in agreement qualitatively with theoretical consideration.