Collective modes in two- and three-dimensional electron systems with Rashba spin-orbit coupling
Collective modes in two- and three-dimensional electron systems with Rashba spin-orbit coupling
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具有 Rashba 自旋轨道耦合的二维和三维电子系统中的集体模式
DOI：
10.1103/physrevb.91.035106
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发表时间：
2014
影响因子：
3.7
通讯作者：
D. Maslov
中科院分区：
文献类型：
--
作者：
S. Maiti;V. Zyuzin;D. Maslov
除了电荷等离子体外，具有Rashba型自旋-轨道耦合(SOC)的2D电子系统还支持自旋扇区的三个集体模：手征-自旋模。在任意强SOC的广义随机位相近似下，我们研究了二维和三维系统中电荷模和自旋模的色散及其相互耦合。在2D和3D中，我们发现电荷等离子体只与三个手征自旋模中的一个耦合。结果表明，这种耦合对有限波数的模式色散有影响，但对零波数的模式色散没有影响。在三维空间中，手性自旋模受到粒子-空穴激发的强烈抑制，而由于弱电子-电子相互作用而消失。三维手征自旋模的朗道衰减与二维不同，自旋分裂的子带之间不存在空穴激发空隙。这种无间隙的连续体也是电荷等离子激元在3D中朗道衰减的原因--这是SOC系统的一个质的新特征。我们还讨论了干净的2D和3D系统的光学传导性，表明SOC在有限频率上引入了谱权，从而满足求和规则。在有限数目的光学电导中，平面内横向手征自旋模式表现为色散峰，这可以在有衍射光栅存在的情况下测量。我们还讨论了在半导体量子阱中手征自旋模的可能的实验表现，如InGaAs/AlGaAs和BiTeI族的3D巨型Rashba材料。
In addition to charge plasmons, a 2D electron system with Rashba-type spin-orbit coupling (SOC) also supports three collective modes in the spin sector: the chiral-spin modes. We study the dispersions of the charge and spin modes and their coupling to each other within a generalized Random Phase Approximation for arbitrarily strong SOC, and both in 2D and 3D systems. In both 2D and 3D, we find that the charge plasmons are coupled to only one of the three chiral-spin modes. This coupling is shown to affect the dispersions of the modes at finite but not at zero wavenumbers. In 3D, the chiral-spin modes are strongly damped by particle-hole excitations and disappear for weak electron-electron interaction. Landau damping of the chiral-spin modes in 3D is directly related to the fact that, in contrast to 2D, there is no gap for particle-hole excitations between spin-split subbands. The gapless continuum is also responsible for Landau damping of the charge plasmon in 3D - a qualitatively new feature of the SOC system. We also discuss the optical conductivity of clean 2D and 3D systems and show that SOC introduces spectral weight at finite frequency in a such way that the sum rule is satisfied. The in-plane tranverse chiral-spin mode shows up as dispersing peak in the optical conductivity at finite number which can can be measured in the presence of diffraction grating. We also discuss possible experimental manifestations of chiral-spin modes in semiconductor quantum wells such InGaAs/AlGaAs and 3D giant Rashba materials of the BiTeI family.