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中国物理学会期刊

光场辐照下稀磁半导体/半导体超晶格中自旋电子输运特性研究

Spin-polarized transport properties in diluted-magnetic-semiconductor/semiconductor superlattices under light-field assisted

CSTR: 32037.14.aps.72.20230935
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  • 基于单电子有效质量近似理论和传递矩阵方法, 理论研究了稀磁半导体/半导体超晶格结构中电子的自旋极化输运特性. 主要讨论了光场和磁场联合调制对自旋极化输运的影响, 以及不同自旋电子在该超晶格结构中的隧穿时间. 理论和数值计算结果表明, 由于导带电子与掺杂Mn 离子之间的sp-d 电子相互作用引起巨塞曼劈裂, 因此在磁场调制下, 不同自旋电子在该结构中感受到的势函数不同而呈现出自旋过滤效应, 不同自旋电子的共振透射能带的位置和宽度可以通过磁场进行调制. 同时在该结构中考虑光场时, 自旋依赖的透射谱会因为吸收和发射光子而呈现出对光场的强度和频率响应; 最后, 通过不同自旋电子的高斯波包在该结构中随时间的演化给出了不同自旋电子的隧穿时间. 本文研究结果对研究和设计基于稀磁半导体/半导体超晶格结构的高速量子器件具有一定的指导意义.

     

    Based on the single electron effective mass approximation theory and the transfer-matrix method, the spin polarized transport properties of electrons in a diluted-magnetic-semiconductor/semiconductor superlattice are studied. The influence of a light-field and a magnetic-field on spin polarized transport and the tunneling time in the superlattice structure are discussed in more detail. The results show that, due to the sp-d electron interaction between conduction band electrons and doped Mn ions, giant Zeeman splitting occurs. It is shown that a significant spin-dependent transmission and the position and width of the resonant-transmission-band of spin-dependent electron can be manipulated by adjusting the magnetic- and light-field. Considering the light field irradiation, the resonance band of electron is deformed and broadened with the increase of the light field intensity. For the case of a strong magnetic field, the transmission coefficient (TC) in the low-energy region is almost zero when the light field is not added, but with the increase of light intensity, the TC increased significantly in the zone increases significantly, that is, a quasi-bound band appears. These features are due to the energy exchange between electrons and the light field when electrons tunnel through the superlattice structure under light irradiation. In addition, light and magnetic fields can significantly change the spin polarization of electrons. Under a certain magnetic field intensity (B = 2 T), the light field significantly changes the spin polarization of electrons, the main effect is that the width of the spin polarization platform narrows and oscillatory peaks are accompanied on both sides of the platform. This effect is strengthened with the increase of the light field intensity. However, when the magnetic field is stronger (B = 5 T), the opposite is true. These show that the spin polarization can be modulated by the light field. Finally, the tunneling time of spin-up and spin-down electrons is studied by the evolution of Gaussian wave packets in the structure. The results show that the tunneling time depends on a spin of electrons, and it can be seen that the tunneling time of the spin-down electron is shorter than that of the spin-up electron in the superlattice structure. These remarkable properties of spin polarized transport may be beneficial for the devising tunable spin filtering devices based on diluted magnetic semiconductor/semiconductor superlattice structure.

     

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