Magnetic ground state of an individual Fe(2+) ion in strained semiconductor nanostructure.
Magnetic ground state of an individual Fe(2+) ion in strained semiconductor nanostructure.
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DOI：
10.1038/ncomms10484
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发表时间：
2016-01-28
影响因子：
16.6
通讯作者：
Pacuski W
中科院分区：
文献类型：
--
作者：
Smoleński T;Kazimierczuk T;Kobak J;Goryca M;Golnik A;Kossacki P;Pacuski W
具有非零自旋和多基态的单杂质提供了可用于存储量子信息的自由度。然而，Fe2+掺杂剂在块体半导体中具有单一的非简并基态，因此在自旋电子应用中用处不大。在这里，我们展示了通过使Fe2+离子受到高应变，例如，由晶格失配的外延纳米结构产生的高应变，可以改变已建立的Fe2+自旋组态的图像。我们的分析表明，高应变引起了离子能谱的质变，并导致了自旋投射Sz=±2的近双简并基态。我们用一个新的系统--包含单个Fe2+离子的应变外延量子点--对这一概念提供了实验证明。利用受限激子与单铁杂质之间的耦合作用，在光致发光实验中揭示了CdSe/ZnSe点中Fe2+基态的磁性特征。我们还证明了Fe2+自旋可以被自旋极化激子定向，这为将其用作光学可控的无核自旋涨落的二能级系统提供了可能性。镶嵌在半导体基质中的Fe~(2+)离子在基态通常为零磁矩。在这里，作者从理论和实验上证明，当铁离子在外延量子点中受到应变时，会产生几乎双简并的磁性基态，这表明它们可以用于自旋电子学和孤子电子学。
Single impurities with nonzero spin and multiple ground states offer a degree of freedom that can be utilized to store the quantum information. However, Fe2+ dopant is known for having a single nondegenerate ground state in the bulk host semiconductors and thus is of little use for spintronic applications. Here we show that the well-established picture of Fe2+ spin configuration can be modified by subjecting the Fe2+ ion to high strain, for example, produced by lattice mismatched epitaxial nanostructures. Our analysis reveals that high strain induces qualitative change in the ion energy spectrum and results in nearly doubly degenerate ground state with spin projection Sz=±2. We provide an experimental proof of this concept using a new system: a strained epitaxial quantum dot containing individual Fe2+ ion. Magnetic character of the Fe2+ ground state in a CdSe/ZnSe dot is revealed in photoluminescence experiments by exploiting a coupling between a confined exciton and the single-iron impurity. We also demonstrate that the Fe2+ spin can be oriented by spin-polarized excitons, which opens a possibility of using it as an optically controllable two-level system free of nuclear spin fluctuations. Iron Fe2+ ions embedded in semiconductor matrix usually have zero magnetic moment in the ground state. Here, the authors show theoretically and experimentally that a nearly doubly degenerate magnetic ground state is produced when iron ions are subjected to strain in epitaxial quantum dots, suggesting they could be used in spintronics and solotronics.