Magnetic-field-dependent excitation transfer in quantum wells of diluted magnetic semiconductor
Magnetic-field-dependent excitation transfer in quantum wells of diluted magnetic semiconductor
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DOI：
10.1007/s00339-013-8005-8
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发表时间：
2014-04
期刊：
影响因子：
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通讯作者：
K. Uchiyama;S. Kubota;T. Matsumoto;Kiyoshi Kobayashi;H. Hori
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文献类型：
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作者：
K. Uchiyama;S. Kubota;T. Matsumoto;Kiyoshi Kobayashi;H. Hori
本文利用扫描近场光学显微镜研究了稀释磁性半导体双量子阱在7 K和9 t外磁场下的激发转移。在每个量子阱中，层厚和磁性组分掺杂浓度的局部波动产生了局部能量最小值。激子放松到局部能量最小值，并通过近场光相互作用在最小值之间转移，甚至跨越量子阱，向稳定的位置转移。我们测量了不同外磁场下近场光致发光的强度图，空间分辨率估计为30 nm。通过扫描隧道显微镜图像证实了测量位置的重复性。对这些图的分析推导出每个量子阱的激子局域位置的典型尺寸对磁场的依赖性。基于这些结果，我们研究了双量子阱系统中不同层的两个量子阱之间的激发转移，并表明激子转移发生在两个特定的外加磁场强度下，导致两个不同量子阱的塞曼分裂能级交叉。我们得出结论，激子的局域化和量子阱间转移都可以由外部磁场控制。这为功能设备在没有任何布线的情况下运行提供了基础。
We studied the excitation transfer in double quantum wells of a diluted magnetic semiconductor using a scanning near-field optical microscope at 7 K in external magnetic fields up to 9 T. In each quantum well, local energy minima are generated by local fluctuation of layer thickness and doping concentration of magnetic components. Excitons relax into the local energy minima and transfer between the minima via near-field optical interactions even across quantum wells toward stable sites at which to localize. We measured the intensity maps of near-field photoluminescence with spatial resolution estimated to be 30 nm under varying external magnetic fields. The measurement position reproducibility was confirmed by scanning tunneling microscope images. Analysis of the maps derived the magnetic-field dependence of the typical size of exciton-localization sites for each quantum well. Based on these results, we investigated the excitation transfer between the two quantum wells lying in different layers of the double quantum well system, and showed that the exciton transfer takes place at the two specific applied magnetic-field intensities that result in the crossing of Zeeman-split energy levels of the two different wells. We concluded that both the localization and the inter-quantum-well transfer of excitons are able to be controlled by an external magnetic field. This provides the basis for functional devices operating without any wiring.