Macroscopic transverse drift of long current-induced spin coherence in two-dimensional electron gases

Abstract

We imaged the transport of current-induced spin coherence in a two-dimensional electron gas confined in a triple quantum well. Nonlocal Kerr rotation measurements, based on the optical resonant amplification of the electrically-induced polarization, revealed a large spatial variation of the electron g factor and the efficient generation of a current-controlled spin-orbit field in a macroscopic Hall bar device. We observed coherence times in the nanoseconds range transported beyond half-millimeter distances in a direction transverse to the applied electric field. The measured long spin transport length can be explained by two material properties: large mean free path for charge diffusion in clean systems and enhanced spin-orbit coefficients in the triple well. arXiv:1605.06854v3 [cond-mat.mes-hall]

Optical control and detection of spin coherence in multilayer systems.

“…The peak with lower frequency corresponds to the lower density in the third subband, and the other two correspond to similar densities in the first and second subband. The first two subbands are almost degenerate (∆ 12 ∼ 0) as confirmed by calculation [31]. We found that ∆ 12 is very sensitive to the width of the lateral wells (increasing rapidly for smaller widths).…”

“…the band gap energy, the Kerr rotation extrema occur in the opposite direction. A similar observation of Kerr rotation extrema occurring on either side of the band gap has been reported in TRKR study of similar multilayer system [31]. The signal at λ = 819 nm included two exponential decay and was fitted to a bi-exponential decay function.…”

“…3.4.2 for more details). The shape of the resulting wavefunction can be deduced by solving the Schröedinger and Poisson equations for the finite square well potential [31].…”

“…In this chapter, we report on the experimental observation of large spin relaxation anisotropy in triple quantum wells (Sample B). Similar multiple quantum well systems have allowed the discovery of interesting phenomena, such as intrinsic spin Hall effect [172], collapse of the integer quantum Hall effect [140,141], long-lived spin coherence [142], spontaneous interlayer phase coherence [143][144][145], control and drift current induced spin polarization [31,83], and excitonic Bose condensation [146][147][148]. Here, we found long relaxation times for the spins oriented along growth direction and fast relaxation times for the spins oriented in-plane.…”

“…This may be explained considering the additional experimental difficulty originated from the fact that the variation with the drift is smaller for B SO than for g, since B SO depends only linearly on V d (see section III.c of Ref. [31]).…”