We study the frequency dependent spin- and charge- conductivity tensors of a two-dimensional electron gas (2DEG) with Rashba and Dresselhaus spin-orbit interaction. We show that the angular anisotropy of the spin-splitting energy induced by the interplay between the Rashba and Dresselhaus couplings gives rise to a characteristic spectral behavior of the spin and charge response which is significantly different from that of pure Rashba or Dresselhaus case. Such new spectral structures open the possibility for control of the optical response by applying an external bias and/or by adjusting the light frequency. In addition, it is shown that the relative strength of the spin-orbit coupling parameters can be obtained through optical probing.Comment: 13 pages, 4 figures. Revised versio
The dynamics of excited electronic states at Ag surfaces is studied by evaluating the quasiparticle selfenergy within the GW approximation. The screened Coulomb interaction W is shown to be sensitive to the spatial variation of s-d screening near the surface. In the region of s-electron spill-out electronic damping is stronger than in the bulk due to the reduced s-d polarization, giving rise to shorter surface-state lifetimes. The lifetime of Ag image states is expected to be strongly reduced due to decay into surface plasmons.
Using the recently proposed definition of a conserved spin-current operator ͓J. Shi et al., Phys. Rev. Lett. 96, 076604 ͑2006͔͒, we explore the frequency dependent spin Hall conductivity for a two-dimensional electron gas with Rashba and Dresselhaus spin-orbit interaction in response to an oscillating electric field. We show that the optical spectrum of the spin Hall conductivity exhibits remarkable changes when the definition of a conserved spin current is applied. Such behavior is mainly due to a significant contribution of the spin-torque term which is absent in the conventional form of the spin current. In addition, it is observed that the magnitude and direction of the dynamic spin Hall current strongly depend on the electric field frequency as with the interplay of the spin-orbit coupling strengths.
Published online zzz PACS 73.63. Kv, 73.21.La, 72.25.Dc We present calculations of the frequency-dependent spin susceptibility tensor of a two-dimensional electron gas with competing Rashba and Dresselhaus spin-orbit interaction. It is shown that the interplay between both types of spin-orbit coupling gives rise to an anisotropic spectral behavior of the spin density response function which is significantly different from that of vanishing Rashba or Dresselhaus case. Strong resonances are developed in the spin susceptibility as a consequence of the angular anisotropy of the energy spin-splitting. This characteristic optical modulable response may be useful to experimentally probe spin accumulation and spin density currents in such systems.Copyright line will be provided by the publisher Electrical manipulation of the electron and hole spins without the need of ferromagnetic materials and/or external magnetic fields is nowadays one of the central aspects in the field of spintronics. [1, 2, 3] The presence of a sizeable spin-orbit interaction (SOI) in low-dimensional semiconductor structures and its modulation possibility (through electrical gating) make it a very prominent mechanism for the access and manipulation of the carriers spin states.It has been established that the dominant contributions to the SOI in quasi-two dimensional electron gases (2DEG) are the so called Rashba and Dresselhaus SO couplings.[4] The former results from the asymmetry of the confining potential that creates the 2DEG, while the latter arises due to the inversion asymmetry of the bulk. Several interesting effects and spin-based devices relying in these SOI mechanisms have been predicted and proposed in the last few years. For instance, the celebrated spin transistor proposed by Datta and Das [5], and its recent non-ballistic version [6]. An intrinsic spin Hall effect in which a transverse spin current is driven by a dc electric field (without a net charge current) has been also predicted to occur due to SOI effects. [7,8,9] More recently, a spin (Hall) accumulation has been observed through optical measurements [10,11,12], and lately, a purely electrical detection of a spin Hall current has been reported.[13] Electric-field-induced spin orientation in SOI coupled systems [14,15,16,17,18] and strained semiconductors has been also explored. [19] On the other hand, the spin-splitting caused by SOI in electron systems opens the possibility of resonant effects via transitions between the spin-split states as a response to alternating electric fields. [20,21,22,23,24,25] The importance of the study of such SOI effects in the dynamical regime (frequency dependent response) has been emphasized by several authors studying a variety of physical aspects, including spin and charge optical conductivities [22], optical absorption spectra [25,26], optical control of the spin Hall current through intense ac probing fields [27], electron-electron interaction effects [28,29], electronphonon interaction on spin Hall currents [30], plasmon modes [23,31...
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