Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Generation, transport and detection of valley-locked spin photocurrent in WSe2–graphene–Bi2Se3 heterostructures


Quantum optoelectronic devices capable of isolating a target degree of freedom (DoF) from other DoFs have allowed for new applications in modern information technology. Many works on solid-state spintronics have focused on methods to disentangle the spin DoF from the charge DoF1, yet many related issues remain unresolved. Although the recent advent of atomically thin transition metal dichalcogenides (TMDs) has enabled the use of valley pseudospin as an alternative DoF2,3, it is nontrivial to separate the spin DoF from the valley DoF since the time-reversal valley DoF is intrinsically locked with the spin DoF4. Here, we demonstrate lateral TMD–graphene–topological insulator hetero-devices with the possibility of such a DoF-selective measurement. We generate the valley-locked spin DoF via a circular photogalvanic effect in an electric-double-layer WSe2 transistor. The valley-locked spin photocarriers then diffuse in a submicrometre-long graphene layer, and the spin DoF is measured separately in the topological insulator via non-local electrical detection using the characteristic spin–momentum locking. Operating at room temperature, our integrated devices exhibit a non-local spin polarization degree of higher than 0.5, providing the potential for coupled opto-spin–valleytronic applications that independently exploit the valley and spin DoFs.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: Proposed device scheme and electrical characterization of WSe2–graphene–TI heterostructures
Fig. 2: Light-helicity-dependent local photocurrent response of WSe2 and Bi2Se3.
Fig. 3: Non-local CPGE measurements and gate-dependent local/non-local polarizability.


  1. 1.

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

    Article  Google Scholar 

  2. 2.

    Mak, K. F., Lee, C., Hone, J., Shan, J. & Heinz, T. F. Atomically thin MoS2: a new direct-gap semiconductor. Phys. Rev. Lett. 105, 136805 (2010).

    Article  Google Scholar 

  3. 3.

    Zeng, H., Dai, J., Yao, W., Xiao, D. & Cui, X. Valley polarization in MoS2 monolayers by optical pumping. Nat. Nanotech. 7, 490–493 (2012).

    CAS  Article  Google Scholar 

  4. 4.

    Xiao, D., Liu, G. B., Feng, W., Xu, X. & Yao, W. Coupled spin and valley physics in monolayers of MoS2 and other group-VI dichalcogenides. Phys. Rev. Lett. 108, 196802 (2012).

    Article  Google Scholar 

  5. 5.

    Kato, Y., Myers, R., Gossard, A. & Awschalom, D. Observation of the spin Hall effect in semiconductors. Science 306, 1910–1913 (2004).

    CAS  Article  Google Scholar 

  6. 6.

    Rokhinson, L., Pfeiffer, L. & West, K. Spontaneous spin polarization in quantum point contacts. Phys. Rev. Lett. 96, 156602 (2006).

    CAS  Article  Google Scholar 

  7. 7.

    Watson, S. K., Potok, R., Marcus, C. & Umansky, V. Experimental realization of a quantum spin pump. Phys. Rev. Lett. 91, 258301 (2003).

    Article  Google Scholar 

  8. 8.

    Ganichev, S. et al. Spin-galvanic effect. Nature 417, 153–156 (2002).

    CAS  Article  Google Scholar 

  9. 9.

    Fert, A. & Jaffres, H. Conditions for efficient spin injection from a ferromagnetic metal into a semiconductor. Phys. Rev. B 64, 184420 (2001).

    Article  Google Scholar 

  10. 10.

    Wunderlich, J. et al. Spin Hall effect transistor. Science 330, 1801–1804 (2010).

    CAS  Article  Google Scholar 

  11. 11.

    Srivastava, A. et al. Valley Zeeman effect in elementary optical excitations of monolayer WSe2. Nat. Phys. 11, 141–147 (2015).

    CAS  Article  Google Scholar 

  12. 12.

    Zhong, D. et al. Van der Waals engineering of ferromagnetic semiconductor heterostructures for spin and valleytronics. Sci. Adv. 3, e1603113 (2017).

    Article  Google Scholar 

  13. 13.

    Kim, J. et al. Ultrafast generation of pseudo-magnetic field for valley excitons in WSe2 monolayers. Science 346, 1205–1208 (2014).

    CAS  Article  Google Scholar 

  14. 14.

    Yuan, H. et al. Generation and electric control of spin–valley-coupled circular photogalvanic current in WSe2. Nat. Nanotech. 9, 851–857 (2014).

    CAS  Article  Google Scholar 

  15. 15.

    Han, W. & Kawakami, R. K. Spin relaxation in single-layer and bilayer graphene. Phys. Rev. Lett. 107, 047207 (2011).

    Article  Google Scholar 

  16. 16.

    Fu, L., Kane, C. L. & Mele, E. J. Topological insulators in three dimensions. Phys. Rev. Lett. 98, 106803 (2007).

    Article  Google Scholar 

  17. 17.

    Xia, Y. et al. Observation of a large-gap topological-insulator class with a single Dirac cone on the surface. Nat. Phys. 5, 398–402 (2009).

    CAS  Article  Google Scholar 

  18. 18.

    Ganichev, S. D. & Prettl, W. Spin photocurrents in quantum wells. J. Phys. Condens. Matter 15, R935–R983 (2003).

    CAS  Article  Google Scholar 

  19. 19.

    McIver, J. W., Hsieh, D., Steinberg, H., Jarillo-Herrero, P. & Gedik, N. Control over topological insulator photocurrents with light polarization. Nat. Nanotech. 7, 96–100 (2011).

    CAS  Article  Google Scholar 

  20. 20.

    Eginligil, M. et al. Dichroic spin-valley photocurrent in monolayer molybdenum disulphide. Nat. Commun. 6, 7636 (2015).

    Article  Google Scholar 

  21. 21.

    Yuan, H. et al. Zeeman-type spin splitting controlled by an electric field. Nat. Phys. 9, 563–569 (2013).

    CAS  Article  Google Scholar 

  22. 22.

    Duan, J. et al. Identification of helicity-dependent photocurrents from topological surface states in Bi2Se3 gated by ionic liquid. Sci. Rep. 4, 4889 (2014).

    CAS  Article  Google Scholar 

  23. 23.

    Okada, K. N. et al. Enhanced photogalvanic current in topological insulators via Fermi energy tuning. Phys. Rev. B 93, 081403(R) (2016).

    Article  Google Scholar 

  24. 24.

    Guimarães, M. et al. Controlling spin relaxation in hexagonal BN-encapsulated graphene with a transverse electric field. Phys. Rev. Lett. 113, 086602 (2014).

    Article  Google Scholar 

  25. 25.

    Heo, H. et al. Interlayer orientation-dependent light absorption and emission in monolayer semiconductor stacks. Nat. Commun. 6, 7372 (2015).

    CAS  Article  Google Scholar 

  26. 26.

    Ogawa, N., Bahramy, M. S., Kaneko, Y. & Tokura, Y. Photocontrol of Dirac electrons in a bulk Rashba semiconductor. Phys. Rev. B 90, 125122 (2014).

    Article  Google Scholar 

  27. 27.

    Bychkov, Y. A. & Rashba, E. Properties of a 2D electron gas with lifted spectral degeneracy. JETP Lett. 39, 78–81 (1984).

    Google Scholar 

  28. 28.

    Zhu, C. et al. Exciton valley dynamics probed by Kerr rotation in WSe2 monolayers. Phys. Rev. B 90, 161302 (2014).

    Article  Google Scholar 

  29. 29.

    Kim, J. et al. Observation of ultralong valley lifetime in WSe2/MoS2 heterostructures. Sci. Adv. 3, e1700518 (2017).

    Article  Google Scholar 

  30. 30.

    Hao, K. et al. Direct measurement of exciton valley coherence in monolayer WSe2. Nat. Phys. 12, 677–682 (2016).

    CAS  Article  Google Scholar 

  31. 31.

    Appelbaum, I. Introduction to spin-polarized ballistic hot electron injection and detection in silicon. Phil. Trans. R. Soc. A 369, 3554–3574 (2011).

    CAS  Article  Google Scholar 

  32. 32.

    Kamalakar, M. V., Dankert, A., Bergsten, J., Ive, T. & Dash, S. P. Enhanced tunnel spin injection into graphene using chemical vapor deposited hexagonal boron nitride. Sci. Rep. 4, 6146 (2014).

    CAS  Article  Google Scholar 

  33. 33.

    Noh, H.-J. et al. Controlling the evolution of two-dimensional electron gas states at a metal/Bi2Se3 interface. Phys. Rev. B 91, 121110(R) (2015).

    Article  Google Scholar 

Download references


This work was supported by Samsung Research Funding Centre of Samsung Electronics under project number SRFC-MA1402-02.

Author information




S.C. and M.N. contributed equally to this work. H.C. conceived the main idea and designed the experimental protocols. S.C., M.N., J.-H.K., J.S., H.B., D.L., H.S., S.Y., S.L., W.S., C.-H.L., M.-H.J. and D.K. performed the sample fabrication. S.C., S.S., M.N. and J.L. performed the CPGE measurements. H.K. and J.K. provided single crystal Bi2Se3. H.C. supervised the project. S.C., M.N. and H.C. wrote the manuscript with input from all authors.

Corresponding author

Correspondence to Hyunyong Choi.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Figures 1–6, Supplementary Tables 1–3, Supplementary References

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Cha, S., Noh, M., Kim, J. et al. Generation, transport and detection of valley-locked spin photocurrent in WSe2–graphene–Bi2Se3 heterostructures. Nature Nanotech 13, 910–914 (2018).

Download citation

Further reading


Quick links

Find nanotechnology articles, nanomaterial data and patents all in one place. Visit Nano by Nature Research