Browsing by Author "Sheng, WD"

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Theory of excitonic artificial atoms: InGaAs/GaAs quantum dots in strong magnetic fields
(2003-12-01)
Cheng, SJ
;
Sheng, WD
;
Hawrylak, P
;
電子物理學系
;
Department of Electrophysics
We develop a theory of excitonic artificial atoms in strong magnetic fields. The excitonic atoms are formed by N electrons and holes confined in a quantum dot. The single-particle levels are described by the Fock-Darwin spectrum in a magnetic field. The magnetic field induces crossing of energy levels and allows us to engineer degenerate shells. We apply exact diagonalization techniques to calculate the magnetic-field evolution of the ground state of the N-electron-hole complex and its emission spectra. We focus on degenerate shells and show that excitons condense into correlated states due to hidden symmetry. We relate the Fock-Darwin spectrum, hidden symmetries, and direct and exchange interaction among particles to the emission spectra as a function of number of electron-hole pairs (excitation power) and magnetic field.
Theory of excitonic filling factor v=2 quantum Hall droplet in self-assembled quantum dots
(2005)
Chen, SJ
;
Sheng, WD
;
Hawrylak, P
;
電子物理學系
;
Department of Electrophysics
We present a theory of excitonic quantum Hall droplet (EXQHD) at filling factor v = 2 in a self-assembled quantum dot subject to a strong perpendicular magnetic field B. Using the method of configuration interaction the ground and excited states, the stability against spin flips, and die optical emission spectrum of v = 2 EXQHD are calculated in both semi-analytical and numerical manner. The v = 2 EXQHD is found to be stable and its characteristic spin related emission pattern is identified.