Departament de Química Física i Analítica, Universitat Jaume I, E-12080 Castelló, Spain.
J Phys Condens Matter. 2012 Mar 21;24(11):115801. doi: 10.1088/0953-8984/24/11/115801. Epub 2012 Feb 21.
We study the spin purity of the hole ground state in nearly axially symmetric GaN/AlN quantum dots (QDs). To this end, we develop a six-band Burt-Foreman Hamiltonian describing the valence band structure of zinc blende nanostructures with cylindrical symmetry and calculate the effects of eccentricity variationally. We show that the aspect ratio is a key factor for spin purity. In typical QDs with small aspect ratio the ground state is essentially a heavy hole (HH) whose spin purity is even higher than that of InGaAs QDs of similar sizes. When the aspect ratio increases, mixing with light-hole (LH) and split-off (SO) subbands becomes important and, additionally, the ground state becomes sensitive to QD anisotropy, which further enhances the mixing. We finally show that, despite the large GaN hole effective mass, an efficient magnetic modulation is feasible in QDs with aspect ratio ~1, which can be used to modify the ground state symmetry and hence the optical spectrum properties.
我们研究了近轴对称 GaN/AlN 量子点（QD）中孔基态的自旋纯度。为此，我们开发了一个六带 Burt-Foreman 哈密顿量来描述具有圆柱对称性的闪锌矿纳米结构的价带结构，并通过变分法计算了偏心的影响。我们表明，纵横比是自旋纯度的关键因素。在具有小纵横比的典型 QD 中，基态本质上是一个重空穴（HH），其自旋纯度甚至高于类似尺寸的 InGaAs QD。当纵横比增加时，与轻空穴（LH）和分裂空穴（SO）子带的混合变得重要，此外，基态对 QD 各向异性变得敏感，这进一步增强了混合。我们最后表明，尽管 GaN 空穴的有效质量很大，但在纵横比~1 的 QD 中仍可以实现有效的磁场调制，这可以用于修改基态对称性，从而改变光学光谱性质。
