We study theoretically electron states in quantum dots and their excitations by circularly polarized light. First, we calculate the hole states in a quantum dot modeled by three-dimensional harmonic confinement potential. In the bulk direct-gap semiconductors, the k·p perturbation method around F point adequately yields heavy-hole, light-hole and split-off bands. We adopt the effective-mass approximation based on the k-p perturbation method and obtain quantized energy levels for holes in the quantum dot. The ground levels are two-fold degenerate and mainly consist of |j, m> = |3/2, ±3/2> components. It should be mentioned that a small amount of |3/2, ±1/2> components are coherently mixed in the states. Second, we examine an electron-hole excitation by the irradiation of circularly polarized light σ̄. The main component of the exciton is |3/2, -3/2> hole|1/2, -1/2>electron. The electron state |1/2, 1/2>electron is also excited owing to the mixture between |3/2, ±3/2> and |3/2, ±1/2> components in the hole states, which should lead to an inaccuracy in the manipulation of electron spins. The Overhauser field created by nuclear spins plays a role when it is larger than an external magnetic field. It randomizes the direction of electron spins excited by the circularly polarized light a- in an ensemble of self-assembled quantum dots.
|ジャーナル||Physica Status Solidi (C) Current Topics in Solid State Physics|
|出版ステータス||Published - 2008 6 30|
|イベント||15th International Conference on Nonequilibrium Carrier Dynamics in Semiconductors, HCIS15 - Tokyo, Japan|
継続期間: 2007 7 23 → 2007 7 27
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