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Opto-valleytronic imaging of atomically thin semiconductors

Abstract

Transition metal dichalcogenide semiconductors represent elementary components of layered heterostructures for emergent technologies beyond conventional optoelectronics. In their monolayer form they host electrons with quantized circular motion and associated valley polarization and valley coherence as key elements of opto-valleytronic functionality. Here, we introduce two-dimensional polarimetry as means of direct imaging of the valley pseudospin degree of freedom in monolayer transition metal dichalcogenides. Using MoS2 as a representative material with valley-selective optical transitions, we establish quantitative image analysis for polarimetric maps of extended crystals, and identify valley polarization and valley coherence as sensitive probes of crystalline disorder. Moreover, we find site-dependent thermal and non-thermal regimes of valley-polarized excitons in perpendicular magnetic fields. Finally, we demonstrate the potential of wide-field polarimetry for rapid inspection of opto-valleytronic devices based on atomically thin semiconductors and heterostructures.

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Figure 1: Confocal spectroscopy and imaging of extended MoS2 monolayers grown by chemical vapour deposition.
Figure 2: Raster-scan polarimetry of single- and polycrystalline MoS2.
Figure 3: The valley Zeeman effect in polarimetric imaging.
Figure 4: Wide-field linear and circular polarimetry.

References

  1. 1

    Gunawan, O., De Poortere, E. P. & Shayegan, M. AlAs two-dimensional electrons in an antidot lattice: electron pinball with elliptical Fermi contours. Phys. Rev. B 75, 081304 (2007).

    Article  Google Scholar 

  2. 2

    Culcer, D., Saraiva, A. L., Koiller, B., Hu, X. & Das Sarma, S. Valley-based noise-resistant quantum computation using Si quantum dots. Phys. Rev. Lett. 108, 126804 (2012).

    Article  Google Scholar 

  3. 3

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

    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

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

    CAS  Article  Google Scholar 

  6. 6

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

    CAS  Article  Google Scholar 

  7. 7

    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 

  8. 8

    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 

  9. 9

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

    Article  Google Scholar 

  10. 10

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

    CAS  Article  Google Scholar 

  11. 11

    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 

  12. 12

    Zhang, Y. J., Oka, T., Suzuki, R., Ye, J. T. & Iwasa, Y. Electrically switchable chiral light-emitting transistor. Science 344, 725–728 (2014).

    CAS  Article  Google Scholar 

  13. 13

    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 

  14. 14

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

    Article  Google Scholar 

  15. 15

    Lagarde, D. et al. Carrier and polarization dynamics in monolayer MoS2 . Phys. Rev. Lett. 112, 047401 (2014).

    CAS  Article  Google Scholar 

  16. 16

    Jones, A. M. et al. Optical generation of excitonic valley coherence in monolayer WSe2 . Nat. Nanotech. 8, 634–638 (2013).

    CAS  Article  Google Scholar 

  17. 17

    Wang, G. et al. Valley dynamics probed through charged and neutral exciton emission in monolayer WSe2 . Phys. Rev. B 90, 075413 (2014).

    Article  Google Scholar 

  18. 18

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

    CAS  Article  Google Scholar 

  19. 19

    Jones, A. M. et al. Spin-layer locking effects in optical orientation of exciton spin in bilayer WSe2 . Nat. Phys. 10, 130–134 (2014).

    CAS  Article  Google Scholar 

  20. 20

    Zhu, B., Zeng, H., Dai, J., Gong, Z. & Cui, X. Anomalously robust valley polarization and valley coherence in bilayer WS2 . Proc. Natl Acad. Sci. USA 111, 11606–11611 (2014).

    CAS  Article  Google Scholar 

  21. 21

    Meier, F. & Zakharchenya, B. P. (eds.) Optical Orientation (Elsevier Science, 1984).

    Google Scholar 

  22. 22

    Maialle, M. Z., de Andrada e Silva, E. A. & Sham, L. J. Exciton spin dynamics in quantum wells. Phys. Rev. B 47, 15776–15788 (1993).

    CAS  Article  Google Scholar 

  23. 23

    Glazov, M. M. et al. Exciton fine structure and spin decoherence in monolayers of transition metal dichalcogenides. Phys. Rev. B 89, 201302 (2014).

    Article  Google Scholar 

  24. 24

    Yu, T. & Wu, M. W. Valley depolarization due to intervalley and intravalley electron-hole exchange interactions in monolayer MoS2 . Phys. Rev. B 89, 205303 (2014).

    Article  Google Scholar 

  25. 25

    Tongay, S. et al. Defects activated photoluminescence in two-dimensional semiconductors: interplay between bound, charged, and free excitons. Sci. Rep. 3, 2657 (2013).

    Article  Google Scholar 

  26. 26

    Van der Zande, A. M. et al. Grains and grain boundaries in highly crystalline monolayer molybdenum disulphide. Nat. Mater. 12, 554–561 (2013).

    CAS  Article  Google Scholar 

  27. 27

    Najmaei, S. et al. Vapour phase growth and grain boundary structure of molybdenum disulphide atomic layers. Nat. Mater. 12, 754–759 (2013).

    CAS  Article  Google Scholar 

  28. 28

    Srivastava, A. et al. Optically active quantum dots in monolayer WSe2 . Nat. Nanotech. 10, 491–496 (2015).

    CAS  Article  Google Scholar 

  29. 29

    He, Y.-M. et al. Single quantum emitters in monolayer semiconductors. Nat. Nanotech. 10, 497–502 (2015).

    CAS  Article  Google Scholar 

  30. 30

    Koperski, M. et al. Single photon emitters in exfoliated WSe2 structures. Nat. Nanotech. 10, 503–506 (2015).

    CAS  Article  Google Scholar 

  31. 31

    Chakraborty, C., Kinnischtzke, L., Goodfellow, K. M., Beams, R. & Vamivakas, A. N. Voltage-controlled quantum light from an atomically thin semiconductor. Nat. Nanotech. 10, 507–511 (2015).

    CAS  Article  Google Scholar 

  32. 32

    Wang, G. et al. Giant enhancement of the optical second-harmonic emission of WSe2 monolayers by laser excitation at exciton resonances. Phys. Rev. Lett. 114, 097403 (2015).

    CAS  Article  Google Scholar 

  33. 33

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

    Article  Google Scholar 

  34. 34

    Li, Y. et al. Valley splitting and polarization by the Zeeman effect in monolayer MoSe2 . Phys. Rev. Lett. 113, 266804 (2014).

    Article  Google Scholar 

  35. 35

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

    CAS  Article  Google Scholar 

  36. 36

    Aivazian, G. et al. Magnetic control of valley pseudospin in monolayer WSe2 . Nat. Phys. 11, 148–152 (2015).

    CAS  Article  Google Scholar 

  37. 37

    MacNeill, D. et al. Breaking of valley degeneracy by magnetic field in monolayer MoSe2 . Phys. Rev. Lett. 114, 037401 (2015).

    Article  Google Scholar 

  38. 38

    Wang, G. et al. Magneto-optics in transition metal diselenide monolayers. 2D Mater. 2, 034002 (2015).

    Article  Google Scholar 

  39. 39

    Stier, A. V., McCreary, K. M., Jonker, B. T., Kono, J. & Crooker, S. A. Exciton diamagnetic shifts and valley Zeeman effects in monolayer WS2 and MoS2 to 65 Tesla. Nat. Commun. 7, 10643 (2016).

    CAS  Article  Google Scholar 

  40. 40

    Cadiz, F. et al. Well separated trion and neutral excitons on superacid treated MoS2 monolayers. Appl. Phys. Lett. 108, 251106 (2016).

    Article  Google Scholar 

  41. 41

    Karzig, T., Bardyn, C.-E., Lindner, N. H. & Refael, G. Topological polaritons. Phys. Rev. X 5, 031001 (2015).

    Google Scholar 

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Acknowledgements

We thank P.M. Ajayan for support in the establishment of materials synthesis conditions used in this study, P. Altpeter and R. Rath for assistance in the clean room, J.P. Kotthaus, B. Urbaszek and F. Wang for useful discussions, and P. Maletinsky and K. Karrai for valuable input on the manuscript. We gratefully acknowledge funding by the European Research Council under the ERC grant agreement no. 336749, the Volkswagen Foundation, the the Deutsche Forschungsgemeinschaft (DFG) Cluster of Excellence Nanosystems Initiative Munich (NIM), and financial support from the Center for NanoScience (CeNS) and LMUinnovativ.

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A.N. and A.H. conceived the experiments. A.N. built the experimental set-up. H.Y. organized the material aspect and prepared MoS2 flakes on SiO2/Si substrates with support from A.D.M. S.N. and J.Lou provided inputs on growth parameters of MoS2 flakes at the initial stage of the project. A.N., M.N. and H.Y. performed basic characterization of the sample. A.N., J.Lin. and L.C. performed the measurements. A.N., J.Lin., L.C. and A.H. analysed the data. A.N. and A.H. prepared the figures and wrote the manuscript. All authors commented on the manuscript.

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Correspondence to Hisato Yamaguchi or Alexander Högele.

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The authors declare no competing financial interests.

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Neumann, A., Lindlau, J., Colombier, L. et al. Opto-valleytronic imaging of atomically thin semiconductors. Nature Nanotech 12, 329–334 (2017). https://doi.org/10.1038/nnano.2016.282

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