Skip to main content

Thank you for visiting nature.com. 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.

Electrical control of the valley Hall effect in bilayer MoS2 transistors

Abstract

The valley degree of freedom of electrons in solids has been proposed as a new type of information carrier, beyond the electron charge and spin1,2,3,4,5,6. The potential of two-dimensional semiconductor transition metal dichalcogenides in valley-based electronic and optoelectronic applications has recently been illustrated through experimental demonstrations of the optical orientation of the valley polarization7,8,9,10 and of the valley Hall effect11 in monolayer MoS2. However, the valley Hall conductivity in monolayer MoS2, a non-centrosymmetric crystal, cannot be easily tuned, which presents a challenge for the development of valley-based applications. Here, we show that the valley Hall effect in bilayer MoS2 transistors can be controlled with a gate voltage. The gate applies an electric field perpendicular to the plane of the material, breaking the inversion symmetry present in bilayer MoS2. The valley polarization induced by the longitudinal electrical current was imaged with Kerr rotation microscopy. The polarization was found to be present only near the edges of the device channel with opposite sign for the two edges, and was out-of-plane and strongly dependent on the gate voltage. Our observations are consistent with symmetry-dependent Berry curvature and valley Hall conductivity in bilayer MoS212.

This is a preview of subscription content

Access options

Buy article

Get time limited or full article access on ReadCube.

$32.00

All prices are NET prices.

Figure 1: MoS2 structure and device characterization.
Figure 2: VHE in bilayer MoS2 (device 1).
Figure 3: Gate dependence of the VHE (device 1).
Figure 4: Gate dependence of the VHE and SHG (device 2).

References

  1. Rycerz, A., Tworzydło, J. & Beenakker, C. W. J. Valley filter and valley valve in graphene. Nature Phys. 3, 172–175 (2007).

    CAS  Article  Google Scholar 

  2. Akhmerov, A. R. & Beenakker, C. W. J. Detection of valley polarization in graphene by a superconducting contact. Phys. Rev. Lett. 98, 157003 (2007).

    CAS  Article  Google Scholar 

  3. Xiao, D., Yao, W. & Niu, Q. Valley-contrasting physics in graphene: magnetic moment and topological transport. Phys. Rev. Lett. 99, 236809 (2007).

    Article  Google Scholar 

  4. Gunawan, O. et al. Valley susceptibility of an interacting two-dimensional electron system. Phys. Rev. Lett. 97, 186404 (2006).

    CAS  Article  Google Scholar 

  5. 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 

  6. Xu, X., Yao, W., Xiao, D. & Heinz, T. F. Spin and pseudospins in layered transition metal dichalcogenides. Nature Phys. 10, 343–350 (2014).

    CAS  Article  Google Scholar 

  7. Mak, K. F., He, K., Shan, J. & Heinz, T. F. Control of valley polarization in monolayer MoS2 by optical helicity. Nature Nanotech. 7, 494–498 (2012).

    CAS  Article  Google Scholar 

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

    CAS  Article  Google Scholar 

  9. Cao, T. et al. Valley-selective circular dichroism of monolayer molybdenum disulphide. Nature Commun. 3, 887 (2012).

    Article  Google Scholar 

  10. Sallen, G. et al. Robust optical emission polarization in MoS2 monolayers through selective valley excitation. Phys. Rev. B 86, 081301(R) (2012).

    Article  Google Scholar 

  11. Mak, K. F., McGill, K. L., Park, J. & McEuen, P. L. The valley Hall effect in MoS2 transistors. Science 344, 1489–1492 (2014).

    CAS  Article  Google Scholar 

  12. Wu, S. et al. Electrical tuning of valley magnetic moment through symmetry control in bilayer MoS2 . Nature Phys. 9, 149–153 (2013).

    CAS  Article  Google Scholar 

  13. Gorbachev, R. V. et al. Detecting topological currents in graphene superlattices. Science 346, 448–451 (2014).

    CAS  Article  Google Scholar 

  14. Sui, M. et al. Gate-tunable topological valley transport in bilayer graphene. Nature Phys. 11, 1027–1031 (2015).

    CAS  Article  Google Scholar 

  15. Shimazaki, Y. et al. Generation and detection of pure valley current by electrically induced Berry curvature in bilayer graphene. Nature Phys. 11, 1032–1036 (2015).

    CAS  Article  Google Scholar 

  16. Lensky, Y. D., Song, J. C. W., Samutpraphoot, P. & Levitov, L. S. Topological valley currents in gapped Dirac materials. Phys. Rev. Lett. 114, 256601 (2015).

    Article  Google Scholar 

  17. 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 

  18. Splendiani, A. et al. Emerging photoluminescence in monolayer MoS2 . Nano Lett. 10, 1271–1275 (2010).

    CAS  Article  Google Scholar 

  19. Liu, G. B., Shan, W.-Y., Yao, Y., Yao, W. & Xiao, D. Three-band tight-binding model for monolayers of group-VIB transition metal dichalcogenides. Phys. Rev. B 88, 085433 (2013).

    Article  Google Scholar 

  20. Kośmider, K., González, J. W. & Fernández-Rossier, J. Large spin splitting in the conduction band of transition metal dichalcogenide monolayers. Phys. Rev. B 88, 245436 (2013).

    Article  Google Scholar 

  21. Cheiwchanchamnangij, T. & Lambrecht, W. R. L. Quasiparticle band structure calculation of monolayer, bilayer, and bulk MoS2 . Phys. Rev. B 85, 205302 (2012).

    Article  Google Scholar 

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

    CAS  Article  Google Scholar 

  23. Sih, V. et al. Spatial imaging of the spin Hall effect and current-induced polarization in two-dimensional electron gases. Nature Phys. 1, 31–35 (2005).

    CAS  Article  Google Scholar 

  24. Gong, Z. et al. Magnetoelectric effects and valley-controlled spin quantum gates in transition metal dichalcogenide bilayers. Nature Commun. 4, 2053 (2013).

    Article  Google Scholar 

  25. Radisavljevic, B., Radenovic, A., Brivio, J., Giacometti, V. & Kis, A. Single-layer MoS2 transistors. Nature Nanotech. 6, 147–150 (2011).

    CAS  Article  Google Scholar 

  26. Tan, Y.-W. et al. Measurement of scattering rate and minimum conductivity in graphene. Phys. Rev. Lett. 99, 246803 (2007).

    Article  Google Scholar 

  27. Malard, L. M., Alencar, T. V., Barboza, A. P. M., Mak, K. F. & de Paula, A. M. Observation of intense second harmonic generation from MoS2 atomic crystals. Phys. Rev. B 87, 201401(R) (2013).

    Article  Google Scholar 

  28. Li, Y. et al. Probing symmetry properties of few-layer MoS2 and h-BN by optical second-harmonic generation. Nano Lett. 13, 3329–3333 (2013).

    CAS  Article  Google Scholar 

  29. Biss, D. P. & Brown, T. G. Polarization-vortex-driven second-harmonic generation. Opt. Lett. 28, 923–925 (2003).

    CAS  Article  Google Scholar 

  30. Abergel, D. S. L., Russell, A. & Fal'Ko, V. I. Visibility of graphene flakes on a dielectric substrate. Appl. Phys. Lett. 91, 063125 (2007).

    Article  Google Scholar 

  31. Mak, K. F. et al. Tightly bound trions in monolayer MoS2 . Nature Mater. 12, 207–211 (2013).

    CAS  Article  Google Scholar 

  32. Lee, C. et al. Anomalous lattice vibrations of single- and few-layer MoS2 . ACS Nano 4, 2695–2700 (2010).

    CAS  Article  Google Scholar 

  33. Lüpke, G. et al. Optical second-harmonic generation as a probe of electric-field-induced perturbation of centrosymmetric media. Opt. Lett. 20, 1997–1999 (1995).

    Article  Google Scholar 

Download references

Acknowledgements

This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences under contract No. DESC0013883 (K.F.M.) and the Air Force Office of Scientific Research under grant FA9550-14-1-0268 (J.S.). Kerr rotation microscopy was supported by the National Science Foundation under Award No. DMR-1410407 and 1420451.

Author information

Authors and Affiliations

Authors

Contributions

All authors conceived and designed the experiments, analyzed the data, and co-wrote the manuscript. J.L. fabricated the MoS2 FET devices and performed the measurements.

Corresponding authors

Correspondence to Kin Fai Mak or Jie Shan.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary information

Supplementary information (PDF 2377 kb)

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Lee, J., Mak, K. & Shan, J. Electrical control of the valley Hall effect in bilayer MoS2 transistors. Nature Nanotech 11, 421–425 (2016). https://doi.org/10.1038/nnano.2015.337

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nnano.2015.337

Further reading

Search

Quick links

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