Abstract
The generation, manipulation and detection of spin-polarized electrons in low-dimensional semiconductors are at the heart of spintronics. Pure spin currents, that is, fluxes of magnetization without charge current, are quite attractive in this respect. A paradigmatic example is the spin Hall effect, where an electrical current drives a transverse spin current and causes a non-equilibrium spin accumulation observed near the sample boundary1,2. Here we provide evidence for an another effect causing spin currents which is fundamentally different from the spin Hall effect. In contrast to the spin Hall effect, it does not require an electric current to flow: without bias the spin separation is achieved by spin-dependent scattering of electrons in media with suitable symmetry. We show, by free-carrier absorption of terahertz (THz) radiation, that spin currents flow in a wide range of temperatures. Moreover, the experimental results provide evidence that simple electron gas heating by any means is already sufficient to yield spin separation due to spin-dependent energy-relaxation processes.
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Acknowledgements
We would like to thank I. Gronwald for help in sample preparation. This work was supported by the DFG through Project GA-501/5, Research Unit FOR370 and Collaborative Research Center SFB689, the RFBR and programs of the RAS. S.G. thanks the HBS and S.A.T. thanks the Foundation ‘Dynasty’–ICFPM and the President Grant for young scientists for support.
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Project planning, model and writing: S.D.G., V.V.B., S.A.T., E.L.I., D.W., W.W., W.P.; experiments and data analysis: S.D.G., V.V.B., S.N.D., S.G., Ch.H.; sample growth and characterization: W.W., Ch.G., D.S., J.S., J.B., G.B.; theory: S.A.T., E.L.I.
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Ganichev, S., Bel’kov, V., Tarasenko, S. et al. Zero-bias spin separation. Nature Phys 2, 609–613 (2006). https://doi.org/10.1038/nphys390
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DOI: https://doi.org/10.1038/nphys390
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