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arXiv 1111.2949cond-mat.mes-hall
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具有Rashba和Dresselhaus自旋-轨道相互作用的一维环在太赫兹脉冲激发下的持续电荷流和自旋流

Persistent charge and spin currents in a 1D ring with Rashba and Dresselhaus spin-orbit interactions by excitation with a terahertz pulse

Marian Nita, Bogdan Ostahie, D. C. Marinescu, Andrei Manolescu, Vidar Gudmundsson

摘要:

持久的,振荡的电荷和自旋电流被示出由两个组件的太赫兹激光脉冲在一维介观环与Rashba-Dresselhaus自旋轨道相互作用(SOI)的电子动量线性驱动。特征干涉效应是由两个SOI耦合对电子自旋施加的相反旋进方向引起的。通过数值求解密度算符的运动方程得到电流的时间依赖性,密度算符随后用于计算少数电子本征态上量子算符的统计平均值。该问题的参数化是根据SOI耦合常数和两个激光器组件之间的相位差来完成的。我们的结果表明,振荡的幅度由两个SOI的相对强度控制,而它们的频率由电子态的激发能之间的差异决定。此外,自旋电流的振荡获得更高频率的拍频模式,我们将其与两个SOI耦合的量子化轴之间的电子自旋章动相关联。这种现象在相同的SOI强度下消失,从而以相同的概率发生相反的进动。

英文摘要:

Persistent, oscillatory charge and spin currents are shown to be driven by a two-component terahertz laser pulse in a one-dimensional mesoscopic ring with Rashba-Dresselhaus spin orbit interactions (SOI) linear in the electron momentum. The characteristic interference effects result from the opposite precession directions imposed on the electron spin by the two SOI couplings. The time dependence of the currents is obtained by solving numerically the equation of motion for the density operator, which is later employed in calculating statistical averages of quantum operators on few electron eigenstates. The parameterization of the problem is done in terms of the SOI coupling constants and of the phase difference between the two laser components. Our results indicate that the amplitude of the oscillations is controlled by the relative strength of the two SOI's, while their frequency is determined by the difference between the excitation energies of the electron states. Furthermore, the oscillations of the spin current acquire a beating pattern of higher frequency that we associate with the nutation of the electron spin between the quantization axes of the two SOI couplings. This phenomenon disappears at equal SOI strengths, whereby the opposite precessions occur with the same probability.

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