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Spin voltage generation through optical excitation of complementary spin populations



By exploiting the spin degree of freedom of carriers inside electronic devices, spintronics has a huge potential for quantum computation and dissipationless interconnects1. Pure spin currents in spintronic devices should be driven by a spin voltage generator, able to drive the spin distribution out of equilibrium without inducing charge currents. Ideally, such a generator should operate at room temperature, be highly integrable with existing semiconductor technology, and not interfere with other spintronic building blocks that make use of ferromagnetic materials. Here we demonstrate a device that matches these requirements by realizing the spintronic equivalent of a photovoltaic generator. Whereas a photovoltaic generator spatially separates photoexcited electrons and holes, our device exploits circularly polarized light to produce two spatially well-defined electron populations with opposite in-plane spin projections. This is achieved by modulating the phase and amplitude of the light wavefronts entering a semiconductor (germanium) with a patterned metal overlayer (platinum). The resulting light diffraction pattern features a spatially modulated chirality inside the semiconductor, which locally excites spin-polarized electrons thanks to electric dipole selection rules2.

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Figure 1: Spin voltage generation and experimental set-up for spatially resolved inverse spin Hall effect (ISHE) measurements.
Figure 2: Measurement of optical spin injection and detection through ISHE.
Figure 3: Simulations and comparison with the experimental data.
Figure 4: Photon energy, excitation power and stripe width dependence of the ISHE signal.


  1. Zutić, I., Fabian, J. & Das Sarma, S. Spintronics: Fundamentals and applications. Rev. Mod. Phys. 76, 323–410 (2004).

    Article  Google Scholar 

  2. Meier, F. & Zakharchenya, B. P. Optical Orientation: Modern Problems in Condensed Matter Sciences Vol. 8 (Elsevier Science, 1984).

    Google Scholar 

  3. Jansen, R. Spintronics: Solar spin devices see the light. Nature Mater. 12, 779–780 (2013).

    Article  CAS  Google Scholar 

  4. Endres, B. et al. Demonstration of the spin solar cell and spin photodiode effect. Nature Commun. 4, 2068 (2013).

    Article  CAS  Google Scholar 

  5. Kondo, T., Hayafuji, J-J. & Munekata, H. Investigation of spin voltaic effect in a p–n heterojunction. Jpn. J. Appl. Phys. 45, L663 (2006).

    Article  CAS  Google Scholar 

  6. Zutić, I., Fabian, J. & Das Sarma, S. Spin-polarized transport in inhomogeneous magnetic semiconductors: Theory of magnetic/nonmagnetic p–n junctions. Phys. Rev. Lett. 88, 066603 (2002).

    Article  Google Scholar 

  7. Zutić, I., Fabian, J. & Das Sarma, S. Spin injection through the depletion layer: A theory of spin-polarized p–n junctions and solar cells. Phys. Rev. B 64, 121201(R) (2001).

    Article  Google Scholar 

  8. Guite, C. & Venkataraman, V. Temperature dependence of spin lifetime of conduction electrons in bulk germanium. Appl. Phys. Lett. 101, 252404 (2012).

    Article  Google Scholar 

  9. Pezzoli, F. et al. Optical spin injection and spin lifetime in Ge heterostructures. Phys. Rev. Lett. 108, 156603 (2012).

    Article  CAS  Google Scholar 

  10. Hochberg, M. & Baehr-Jones, T. Towards fabless silicon photonics. Nature Photon. 4, 492–494 (2010).

    Article  CAS  Google Scholar 

  11. Süess, M. J. et al. Analysis of enhanced light emission from highly strained germanium microbridges. Nature Photon. 7, 466–472 (2013).

    Article  Google Scholar 

  12. Allenspach, R., Meier, F. & Pescia, D. Experimental symmetry analysis of electronic states by spin-dependent photoemission. Phys. Rev. Lett. 51, 2148–2150 (1983).

    Article  CAS  Google Scholar 

  13. Ferrari, A., Bottegoni, F., Isella, G., Cecchi, S. & Ciccacci, F. Epitaxial Si1−xGex alloys studied by spin-polarized photoemission. Phys. Rev. B 88, 115209 (2013).

    Article  Google Scholar 

  14. Lampel, G. Nuclear dynamic polarization by optical electronic saturation and optical pumping in semiconductors. Phys. Rev. Lett. 20, 491–493 (1968).

    Article  CAS  Google Scholar 

  15. Loren, E. J. et al. Hole spin relaxation and intervalley electron scattering in germanium. Phys. Rev. B 84, 214307 (2011).

    Article  Google Scholar 

  16. Sinova, J. & Zutić, I. New moves of the spintronics tango. Nature Mater. 11, 368–371 (2012).

    Article  CAS  Google Scholar 

  17. Jungwirth, T., Wunderlich, J. & Olejník, K. Spin Hall effect devices. Nature Mater. 11, 382–390 (2012).

    Article  CAS  Google Scholar 

  18. McMaster, W. H. Matrix representation of polarization. Rev. Mod. Phys. 33, 8–27 (1961).

    Article  CAS  Google Scholar 

  19. Bottegoni, F. et al. Photoinduced inverse spin Hall effect in Pt/Ge(001) at room temperature. Appl. Phys. Lett. 102, 152411 (2013).

    Article  Google Scholar 

  20. Saitoh, E., Ueda, M., Miyajima, H. & Tatara, G. Conversion of spin current into charge current at room temperature: Inverse spin-Hall effect. Appl. Phys. Lett. 88, 182509 (2006).

    Article  Google Scholar 

  21. Valenzuela, S. O. & Tinkham, M. Direct electronic measurement of the spin Hall effect. Nature 442, 176–179 (2006).

    Article  CAS  Google Scholar 

  22. Rioux, J. & Sipe, J. E. Optical injection and control in germanium: Thirty-band k p theory. Phys. Rev. B 81, 155215 (2010).

    Article  Google Scholar 

  23. Slachter, A., Bakker, F. L., Adam, J-P. & van Wees, B. J. Thermally driven spin injection from a ferromagnet into a non-magnetic metal. Nature Phys. 6, 879–882 (2010).

    Article  CAS  Google Scholar 

  24. Le Breton, J-C. et al. Thermal spin current from a ferromagnet to silicon by Seebeck spin tunnelling. Nature 475, 82–85 (2011).

    Article  CAS  Google Scholar 

  25. Palik D. (ed.) Handbook of Optical Constants of Solids III (Academic, 1998).

  26. Adachi, S. Model dielectric constants of Si and Ge. Phys. Rev. B 38, 12966–12976 (1988).

    Article  CAS  Google Scholar 

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The authors would like to thank L. Duò for fruitful discussions. The CARIPLO foundation is acknowledged for partially funding this work through the NANOGAP (2010-0632) project. The research leading to these results has received funding from the European Union’s Seventh Framework Programme under grant agreement No 613055.

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Authors and Affiliations



M.B. and G.I. fabricated the samples. F.B. and M.C. carried out the measurements. P.B. performed the numerical simulations. M.C., M.F. and F.C. provided the confocal apparatus with light polarization analysis. F.B. and M.C. performed the data analysis. F.C., G.I. and M.F. coordinated the entire work. All the authors contributed to the writing of the manuscript.

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Correspondence to Marco Finazzi.

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The authors declare no competing financial interests.

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Bottegoni, F., Celebrano, M., Bollani, M. et al. Spin voltage generation through optical excitation of complementary spin populations. Nature Mater 13, 790–795 (2014).

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