Hole Mixing in Semiconductor Quantum Rings
Many applications of semiconductor quantum dots rely on the use of valence band holes. A prominent example is current endeavour to develop quantum information science using the spin of holes rather than that of electrons. Understanding the spin and orbital properties of holes is necessary for further progress. In self-assembled InAs/GaAs quantum dots, the hole ground state is mainly formed by the heavy hole subband. However, there is a finite mixing with the light-hole subband which has been shown to be critical in determining the hole spin properties. A large number of works have then investigated the influence of such coupling in dots. Based on k⋅p theory, in this chapter we study the influence of hole subband mixing in self-assembled quantum rings. It is shown that the inner cavity of the ring enhances the light hole component of the ground state. As the quasi-1D limit is approached, the light-hole character becomes comparable to that of the heavy hole. In InAs/GaAs quantum rings strain reduces the coupling, but the mixing is still larger than in quantum dots. Strain also gives rise to unusual phenomena, such as partial localization of the heavy holes inside the repulsive core region. Deviations of quantum rings from the perfect axial symmetry are shown to have a minor influence on the hole mixing.
KeywordsHeavy Hole Light Hole Lateral Confinement Repulsive Core Hole Spin
Support from MICINN project CTQ2011-27324 and UJI-Bancaixa project P1-1A2009-03 is acknowledged.
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