应变InGaAs量子点核自旋的四极谱
Quadrupolar spectra of nuclear spins in strained InGaAs quantum dots
摘要：
自组装量子点（QD）诞生于晶格失配的成分，其中应变起着不可或缺的作用。通过电四极耦合，应变影响磁环境，如核自旋所见。为了指导未来的单量子点核磁共振（NMR）以及动态核自旋极化实验，应变和四极场分布的原子洞察力。已经确定了QD的结构和组成概况的一些含义。量子点几何形状的高纵横比增强了四极相互作用。倾斜的界面引入双轴性和主四极主轴远离生长轴的倾斜;将镓混合到QD中的合金增强了这两个特征，同时降低了四极能量。关于NMR谱，法拉第和Voigt几何形状的调查，解开在第一位的非均匀加宽的延伸和外观的正常禁戒跃迁。此外，它表明，从NMR谱的主要延伸的合金的摩尔分数的单个QD可以推断。通过元素分辨的核磁共振强度，它被发现，在核有一个因素的五个优势超过那些作为。在外部磁场的存在下，四极和塞曼制度之间的边界线提取为1.5 T的In和1.1 T的As核。在这些值的核自旋去极化率得到最大化，由于非共线的长期超精细相互作用与一个居民电子在量子点。
英文摘要：
Self-assembled quantum dots (QDs) are born out of lattice mismatched ingredients where strain plays an indispensable role. Through the electric quadrupolar coupling, strain affects the magnetic environment as seen by the nuclear spins. To guide prospective single-QD nuclear magnetic resonance (NMR) as well as dynamic nuclear spin polarization experiments, an atomistic insight to the strain and quadrupolar field distributions is presented. A number of implications of the structural and compositional profile of the QD have been identified. A high aspect ratio of the QD geometry enhances the quadrupolar interaction. The inclined interfaces introduce biaxiality and the tilting of the major quadrupolar principal axis away from the growth axis; the alloy mixing of gallium into the QD enhances both of these features while reducing the quadrupolar energy. Regarding the NMR spectra, both Faraday and Voigt geometries are investigated, unraveling in the first place the extend of inhomogeneous broadening and the appearance of the normally-forbidden transitions. Moreover, it is shown that from the main extend of the NMR spectra the alloy mole fraction of a single QD can be inferred. By means of the element-resolved NMR intensities it is found that In nuclei has a factor of five dominance over those of As. In the presence of an external magnetic field, the borderlines between the quadrupolar and Zeeman regimes are extracted as 1.5 T for In and 1.1 T for As nuclei. At these values the nuclear spin depolarization rates of the respective nuclei get maximized due to the noncollinear secular hyperfine interaction with a resident electron in the QD.
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