arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 0806.0317cond-mat.mes-hall
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量子环中光诱导的非平衡自旋和电荷极化

Photo-induced, non-equilibrium spin and charge polarization in quantum rings

Zhen-Gang Zhu, Jamal Berakdar

摘要:

研究了具有自旋轨道相互作用的量子环在线偏振、皮秒、非对称电磁脉冲作用下的自旋相关动力学响应。所产生的偶极矩的振荡对环中占据数的奇偶性和自旋轨道耦合的强度敏感。它示出了相关的发射光谱如何可以通过脉冲强度或栅极电压来控制。此外,我们检查如何静态磁通量可以修改的非平衡动力学。在自旋轨道相互作用的存在下,对于顺磁环,所施加的脉冲导致自旋分裂,非平衡局部电荷密度。由此产生的时间自旋极化垂直于光脉冲极化轴,并以自旋分裂电荷密度的频率周期性地振荡。自旋平均非平衡电荷密度相对于脉冲极化轴具有左右对称性。这里提出的计算是适用于在异质结的III-V族和II-VI族半导体含有几百个电子制造的纳米环。

英文摘要:

We investigate the spin-dependent dynamical response of a quantum ring with a spin-orbit interaction upon the application of linearly polarized, picosecond, asymmetric electromagnetic pulses. The oscillations of the generated dipole moment are sensitive to the parity of the occupation number in the ring and to the strength of the spin-orbit coupling. It is shown how the associated emission spectrum can be controlled via the pulse strength or a gate voltage. In addition, we inspect how a static magnetic flux can modify the non-equilibrium dynamics. In presence of the spin-orbit interaction and for a paramagnetic ring, the applied pulse results in a spin-split, non-equilibrium local charge density. The resulting temporal spin polarization is directed perpendicular to the light-pulse polarization axis and oscillates periodically with the frequency of the spin-split charge density. The spin-averaged non-equilibrium charge density possesses a left-right symmetry with respect to the pulse polarization axis. The calculations presented here are applicable to nano-meter rings fabricated in heterojuctions of III-V and II-VI semiconductors containing several hundreds electrons.

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