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Coherent spin transport through dynamic quantum dots


Spin transport and manipulation in semiconductors have been studied intensively with the ultimate goal of realizing spintronic devices. Previous work in GaAs has focused on controlling the carrier density1, crystallographic orientation2 and dimensionality3,4 to limit the electron spin decoherence and allow transport over long distances4,5,6,7. Here, we introduce a new method for the coherent transport of spin-polarized electronic wave packets using dynamic quantum dots (DQDs) created by the piezoelectric field of coherent acoustic phonons8,9,10,11. Photogenerated spin carriers transported by the DQDs in undoped GaAs (001) quantum wells exhibit a spin coherence length exceeding 100 μm, which is attributed to the simultaneous control of the carrier density and the dimensionality12 by the DQDs during transport. In the absence of an applied magnetic field, we observe the precession of the electron spin induced by the internal magnetic field associated with the spin splitting of the conduction band (Dresselhaus term)13. The coherent manipulation of the precession frequency is also achieved by applying an external magnetic field.

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Figure 1: Schematic view of the formation of the DQDs.
Figure 2: Time-integrated photoluminescence image representative of the charge transport by DQDs for different values of Pl.
Figure 3: Spatial dependence of the circular polarization ratio ρz.
Figure 4: Circular polarization ratio ρz from the photoluminescence at M for a fixed distance of 47 μm from G in the presence of an external magnetic field.

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We thank H. T. Grahn and G. S. Solomon for a critical reading of the manuscript and W. Seidel, S. Krauß and M. Höricke for technical support regarding sample fabrication. We would also like to thank the Bundesministerium für Bildung und Forschung for financial support. J.S. is personally grateful to the Alexander von Humboldt Foundation for financial support.

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Correspondence to Paulo V. Santos.

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Stotz, J., Hey, R., Santos, P. et al. Coherent spin transport through dynamic quantum dots. Nature Mater 4, 585–588 (2005).

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