Rodek A, Kazimierczuk T, Bogucki A, Smoleński T, Pacuski W, Kossacki P
Institute of Experimental Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland.
J Phys Condens Matter. 2019 Nov 13;31(45):455301. doi: 10.1088/1361-648X/ab33d9. Epub 2019 Jul 19.
Owing to exchange interaction between the exciton and magnetic ion, a quantum dot embedding a single magnetic ion is a great platform for optical control of individual spin. In particular, a quantum dot provides strong and sharp optical transitions, which give experimental access to spin states of an individual magnetic ion. We show, however, that physics of quantum dot excitons also complicate spin readout and optical spin manipulation in such a system. This is due to electron-hole exchange interaction in anisotropic quantum dots, which affects the polarisation of the emission lines. One of the consequences is that the intensity of spectral lines in a single spectrum are not simply proportional to the population of various spin states of magnetic ion. In order to provide a solution of the above problem, we present a method of extracting both the spin polarisation degree of a neutral exciton and magnetic dopant inside a semiconductor quantum dot in an external magnetic field. Our approach is experimentally verified on a system of CdSe/ZnSe quantum dot containing a single Fe ion. Both the resonant and non-resonant excitation regimes are explored resulting in a record high optical orientation efficiency of dopant spin in the former case. The proposed solutions can be easily expanded to any other system of quantum dots containing magnetic dopants.
由于激子与磁性离子之间的交换相互作用，嵌入单个磁性离子的量子点是对单个自旋进行光学控制的理想平台。特别是，量子点提供了强而尖锐的光学跃迁，这使得能够通过实验获取单个磁性离子的自旋态。然而，我们发现量子点激子的物理特性也会使这种系统中的自旋读出和光学自旋操控变得复杂。这是由于各向异性量子点中的电子 - 空穴交换相互作用，它会影响发射线的偏振。其中一个后果是，单光谱中谱线的强度并不简单地与磁性离子各种自旋态的布居数成正比。为了解决上述问题，我们提出了一种在外部磁场中提取半导体量子点内中性激子和磁性掺杂剂自旋偏振度的方法。我们的方法在含有单个铁离子的CdSe/ZnSe量子点系统上得到了实验验证。研究了共振和非共振激发机制，在前一种情况下实现了掺杂剂自旋创纪录的高光取向效率。所提出的解决方案可以很容易地扩展到任何其他含有磁性掺杂剂的量子点系统。
