The effective mass approximation (EMA) could be an efficient method for the computational study of semiconductor nanostructures with sizes too large to be handled by first-principles calculations, but the scheme to accurately and reliably introduce EMA parameters for given nanostructures remains to be devised. Herein, we report on an EMA approach based on first-principles-derived data, which enables accurate predictions of the optoelectronic properties of quantum nanostructures. For the CdS/ZnS core/shell quantum rods, for which we recently reported its experimental synthesis, we first carry out density functional theory (DFT) calculations for an infinite nanowire to obtain the nanoscopic dielectric constant, effective mass, and Kohn-Sham potential. The DFT-derived data are then transferred to the finite nanorod cases to set up the EMA equations, from which we estimate the photoluminescence (PL) characteristics. Compared with the corresponding method based on bulk EMA parameters and abrupt potential, we confirm that our EMA approach more accurately describes the PL properties of nanorods. We find that, in agreement with the experimentally observed trends, the optical gap of nanorods is roughly determined by the nanorod diameter and the PL intensity is reduced with increasing the nanorod length. The developed methodology is additionally applied to CdSe nanoplatelets, where reliable experimental data became recently available. Here, we again obtain excellent agreements between calculated and measured optical gap values, confirming the generality of our approach. It is finally shown that the abrupt confinement potential approximation most adversely affects the accuracy of EMA simulations.
Collective Coordinate Descriptions of Magnetic Domain Wall Motion in Perpendicularly Magnetized Nanostructures under the Application of In-plane Fields
Coupled-wire descriptions of unconventional quantum states in twisted nanostructures
Institute of Physics, Academia Sinica（中央研究院物理研究所）；National Center for Theoretical Sciences（国家理论科学中心）；Department of Electronics and Electrical Engineering, National Yang Ming Chiao Tung University（国立阳明交通大学电子电气工程学系）
Semiempirical pseudopotential approach for nitride-based nanostructures and {\it ab initio} based passivation of free surfaces
本文提出了一种基于屏蔽原子赝势和\textit{ab initio}计算的半经验赝势方法。这种方法的动机是对能够解决纳米结构的赝势的需求，其中\textit{ab initio}方法在局部密度近似的水平上既太昂贵又不够准确，而介观有效质量方法由于沿着至少一个维度的结构的小尺寸而不适用。在这项工作中，我们改进了传统的赝势方法，通过两个步骤的过程：首先，我们反演了一组自洽确定的屏蔽{ \it ab initio}势在纤锌矿GAN的一系列晶胞体积，从而确定球对称和结构平均的原子势。其次，我们调整的潜力，以重现观察到的激发能。我们发现，调整代表了一个合理的小扰动的潜力，使随后的潜力仍然再现原来的波函数，而激发能显着改善。此外，我们处理的自由表面的悬挂键的钝化，这是相关的纳米线和胶体纳米粒子的研究。我们提出了一种方法，从{ \it ab initio}计算得到钝化赝势。我们应用我们的赝势方法的GAN纳米线的电子结构上的限制效应的探索。
