Waveguide diffusion modes and slowdown of D’yakonov-Perel’ spin relaxation in narrow two-dimensional semiconductor channels

Mal’shukov, A. G.; Chao, K. A.

doi:10.1103/physrevb.61.r2413

Cited by 118 publications

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References 14 publications

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“…However, as Mal'shukov et al pointed out, other mechanisms can limit the eventual suppression of the spin relaxation, e.g., the BIA induces a component of the D'yakonov-Perel' spin relaxation which is independent of the channel width [20]. We would like to note that in a first experimental study, an effective slowing of the Dyakonov Perel spin relaxation mechanism has been observed in conducting channels of n-InGaAs quantum wires [22,44].…”

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confidence: 98%

“…Here, we describe the possibility of an effective suppression of the spin relaxation in the two-dimensional conducting channel of a spin transistor [18][19][20][21]. As a precursor of the one-dimensional limit, long spin relaxation times are expected when the channel width w is smaller than the electronic mean free path l e (w < l e ).…”

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confidence: 99%

“…Another approach to the problem was given by Mal'shukov and Chao, by solving the spin diffusion equation for electrons in the conducting channel [20]. Their solutions showed that there are certain spin diffusion modes with slow spin relaxation rates, if the conducting channel of the spin transistor has got a finite width.…”

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Spin Relaxation: From 2D to 1D

Holleitner

2010

CFN Lectures on Functional Nanostructures - Volume 2

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In inversion asymmetric semiconductors, spin-orbit interactions give rise to very effective relaxation mechanisms of the electron spin. Recent work, based on the dimensionally constrained D'yakonov Perel' mechanism, describes increasing electronspin relaxation times for two-dimensional conducting layers with decreasing channel width. The slow-down of the spin relaxation can be understood as a precursor of the onedimensional limit.

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Spin Relaxation: From 2D to 1D

Holleitner

2010

CFN Lectures on Functional Nanostructures - Volume 2

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“…This effect is accompanied by spin polarization oscillations and spin polarization transfer from the perpendicular to in-plane component. The prospects for creating a semiconductor-based spintronic device [1,2,3,4,5,6] have generated an emphasis on the studies of properties of electron spin polarization in semiconductor nanostructures [7,8,9,10,11,12,13,14,15,16,17]. Great interest has been expressed in dynamics of electron spin polarization [7,8,9,10,11,12].…”

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Dynamics of spin relaxation near the edge of two-dimensional electron gas

Pershin

2005

Physica E: Low-dimensional Systems and Nanostructures

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We report calculations of spin relaxation dynamics of two-dimensional electron gas with spinorbit interaction at the edge region. It is found that the relaxation of spin polarization near the edge is more slow than relaxation in the bulk. That results finally in the spin accumulation at the edge. Time dependence of spin polarization density is calculated analytically and numerically. The mechanism of slower spin relaxation near the edge is related to electrons reflections from the boundary and the lack of the translation symmetry. These reflections partially compensate electron spin precession generated by spin-orbit interaction, consequently making the spin polarization near the edge long living. This effect is accompanied by spin polarization oscillations and spin polarization transfer from the perpendicular to in-plane component. The prospects for creating a semiconductor-based spintronic device [1,2,3,4,5,6] have generated an emphasis on the studies of properties of electron spin polarization in semiconductor nanostructures [7,8,9,10,11,12,13,14,15,16,17]. Great interest has been expressed in dynamics of electron spin polarization [7,8,9,10,11,12]. For instance, spin relaxation dynamics has been studied in two-dimensional electron gas (2DEG) [7,8], twodimensional channels [9,10], open Sinai billiards (2DEG with a lattice of antidots) [11], and ballistic quantum dots [12]. It was found that the sample geometry [11] as well as specific initial conditions [7,8] could have a significant effect on electron spin relaxation.D'yakonov-Perel' (DP) spin relaxation mechanism [18] is the leading spin relaxation mechanism in many important experimental situations. In the framework of DP theory, initially homogeneous electron spin polarization exponentially relaxes to zero (or to some finite equilibrium value) with time. However, DP theory was formulated for the bulk of a sample. Considering electron spin relaxation near the edge of 2DEG, one would expect the same relaxation scenario. This expectation, however, is not correct. We demonstrate in this Letter that the spin relaxation dynamics near the edge is rather unusual and can not be described by a simple exponential law, as follows from the DP theory. We observe a longer spin relaxation time near the edge, spin polarization oscillations and spin polarization transfer from the perpendicular (to 2DEG) to in-plane component.Let us consider a two-dimensional electron gas with the Rashba spin-orbit interaction [19], which couples electron space and spin degrees of freedom:where α is a constant, σ is the Pauli matrix vector corresponding to the electron spin, and p is the momentum of the electron confined in two-dimensional geometry. From the point of view of electron spin, the effect of spin-orbit interaction can be regarded as an effective magnetic field acting on electron spin. Momentum scatterings reorient the direction of this field, thus leading to average spin relaxation (DP relaxation). Intuitively, electron reflections from the 2DEG edges should increase spin relaxa...

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“…In an n-doped bulk semiconductors τ sb can be very long [9], and a large L s will reduce the efficiency of spin injection. This is the same problem encountered in the study of spin injection from ferromagnetic metals into semiconductors [3], which can be overcome [4] with a proper choice of the barrier height…”

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Optoelectric spin injection in semiconductor heterostructures without a ferromagnet

Mal’shukov

Chao

2002

Phys. Rev. B

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We have shown that electron spin density can be generated by a dc current flowing across a pn junction with an embedded asymmetric quantum well. Spin polarization is created in the quantum well by radiative electron-hole recombination when the conduction electron momentum distribution is shifted with respect to the momentum distribution of holes in the spin split valence subbands. Spin current appears when the spin polarization is injected from the quantum well into the n-doped region of the pn junction. The accompanied emission of circularly polarized light from the quantum well can serve as a spin polarization detector. 73.40.Kp, 78.60.Fi One of the most important problems in spintronics is the efficient injection of spin currents into semiconductor structures. A possible way is to inject spin polarization from a ferromagnet by passing a dc current across the interface [1]. If the ferromagnet is metallic, the efficiency of such injection is controversial [2], and the observed weak spin current has been attributed to the large mismatch of spin diffusion constants between the adjacent semiconductor and metal [3]. Spin injection can be enhanced by using an appropriate interface tunneling barrier [4]. On the other hand, rather high degree of spin current polarization has been detected if the spin is injected from magnetic semiconductors [5], although its high efficiency is restricted to low temperatures.In this Letter we propose a new method to use a dc current to inject spin polarization, not from any ferromagnetic material, but from a quantum well (QW) embedded into a pn junction. The spin polarized current is generated during the radiative electron-hole recombination in the QW, accompanied by the emission of circularly polarized light. Our new injection mechanism can be easily explained. It is well known that in a QW which is asymmetric along the growth direction, at each finite wave vector k the spin degeneracy of hole subbands is removed. The corresponding splitting of hole energies increases with k and can reach a quite high value. For example, in a p inversion layer of a GaAs-AlGaAs heterojunction, the splitting of the topmost heavy-hole subband was calculated [6] to be about 5 meV at k=2·10 6 cm −1 . Each of the split states is a linear combination of four angular momentum eigenstates which are specified by the z-component J z =±3/2 and ±1/2. The resulting mean spins of hole states are parallel to the QW interfaces. For a given k the spins in each pair of spin-split subbands have opposite directions, and in a given spin-split subband the mean spin at k is equal and opposite to that at -k. The spin orientations in the topmost heavy-hole subband are shown in Fig. 1, where the Fermi energy µ e (or µ h ) of the quasiequilibrium degenerate electron gas (or hole gas) is indicated. When a σ-spin electron in the k state of the conduction band makes a radiative transition to the topmost heavy-hole subband, as marked by the downward vertical arrow line in Fig. 1, the probability of this process depends on σ beca...

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Waveguide diffusion modes and slowdown of D’yakonov-Perel’ spin relaxation in narrow two-dimensional semiconductor channels

Cited by 118 publications

References 14 publications

Spin Relaxation: From 2D to 1D

Spin Relaxation: From 2D to 1D

Dynamics of spin relaxation near the edge of two-dimensional electron gas

Optoelectric spin injection in semiconductor heterostructures without a ferromagnet

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