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Valleytronics in 2D materials

Nature Reviews Materials volume 1, Article number: 16055 (2016) Cite this article

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Abstract

Semiconductor technology is currently based on the manipulation of electronic charge; however, electrons have additional degrees of freedom, such as spin and valley, that can be used to encode and process information. Over the past several decades, there has been significant progress in manipulating electron spin for semiconductor spintronic devices, motivated by potential spin-based information processing and storage applications. However, experimental progress towards manipulating the valley degree of freedom for potential valleytronic devices has been limited until very recently. We review the latest advances in valleytronics, which have largely been enabled by the isolation of 2D materials (such as graphene and semiconducting transition metal dichalcogenides) that host an easily accessible electronic valley degree of freedom, allowing for dynamic control.

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Figure 1: Valley-dependent carrier transport.
Figure 2: Valley optical coupling of monolayer excitons.
Figure 3: Interlayer valley excitons in 2D semiconductor heterostructures.
Figure 4: Defect-bound valley excitons in monolayer WSe2.
Figure 5: Valley-dependent optoelectronics.

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References

  1. Rycerz, A., Tworzydło, J. & Beenakker, C. W. J. Valley filter and valley valve in graphene. Nat. Phys. 3, 172–175 (2007). This theoretical work reports that graphene structures can show valley-dependent transport effects.

    Article  CAS  Google Scholar 

  2. Shkolnikov, Y., De Poortere, E., Tutuc, E. & Shayegan, M. Valley splitting of AlAs two-dimensional electrons in a perpendicular magnetic field. Phys. Rev. Lett. 89, 226805 (2002).

    Article  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

  4. Thompson, S. E. et al. A 90-nm logic technology featuring strained-silicon. IEEE Trans. Electron Devices 51, 1790–1797 (2004).

    Article  CAS  Google Scholar 

  5. Sham, L., Allen Jr, S., Kamgar, A. & Tsui, D. Valley–valley splitting in inversion layers on a high-index surface of silicon. Phys. Rev. Lett. 40, 472 (1978).

    Article  CAS  Google Scholar 

  6. Ohkawa, J. F. & Uemura, Y. Theory of valley splitting in an N-channel (100) inversion layer of Si I. Formulation by extended zone effective mass theory. J. Phys. Soc. Jpn 43, 907–916 (1977).

    Article  CAS  Google Scholar 

  7. Isberg, J. et al. Generation, transport and detection of valley-polarized electrons in diamond. Nat. Mater. 12, 760–764 (2013).

    Article  CAS  Google Scholar 

  8. Zhu, Z., Collaudin, A., Fauqué, B., Kang, W. & Behnia, K. Field-induced polarization of Dirac valleys in bismuth. Nat. Phys. 8, 89–94 (2012).

    Article  CAS  Google Scholar 

  9. Koiller, B., Hu, X. & Das Sarma, S. Exchange in silicon-based quantum computer architecture. Phys. Rev. Lett. 88, 027903 (2001).

    Article  CAS  Google Scholar 

  10. Goswami, S. et al. Controllable valley splitting in silicon quantum devices. Nat. Phys. 3, 41–45 (2007).

    Article  CAS  Google Scholar 

  11. Yang, C. H. et al. Spin-valley lifetimes in a silicon quantum dot with tunable valley splitting. Nat. Commun. 4 2069 (2013).

    Article  CAS  Google Scholar 

  12. Salfi, J. et al. Spatially resolving valley quantum interference of a donor in silicon. Nat. Mater. 13, 605–610 (2014).

    Article  CAS  Google Scholar 

  13. Yao, W., Xiao, D. & Niu, Q. Valley-dependent optoelectronics from inversion symmetry breaking. Phys. Rev. B 77, 235406 (2008).

    Article  CAS  Google Scholar 

  14. Xiao, D., Yao, W. & Niu, Q. Valley-contrasting physics in graphene: magnetic moment and topological transport. Phys. Rev. Lett. 99, 236809 (2007). This theoretical work reports that graphene with broken inversion symmetry can show various valley-dependent phenomena.

    Article  CAS  Google Scholar 

  15. 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). This theoretical work reports that monolayer TMDs with broken inversion symmetry can show various valley-dependent effects, including a valley-dependent optical selection rule.

    Article  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

  19. Liu, G.-B., Xiao, D., Yao, Y., Xu, X. & Yao, W. Electronic structures and theoretical modelling of two-dimensional group-VIB transition metal dichalcogenides. Chem. Soc. Rev. 44, 2643–2663 (2015).

    Article  CAS  Google Scholar 

  20. Mak, K. F., He, K. L., Shan, J. & Heinz, T. F. Control of valley polarization in monolayer MoS2 by optical helicity. Nat. Nanotechnol. 7, 494–498 (2012). This work and references 21–23 are the first to show that the valley physics of monolayer TMDs is evident by performing helicity-dependent photoluminescence measurements, a consequence of the valley-dependent optical selection rule.

    Article  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

  24. Wolf, S. et al. Spintronics: a spin-based electronics vision for the future. Science 294, 1488–1495 (2001).

    Article  CAS  Google Scholar 

  25. Gorbachev, R. et al. Detecting topological currents in graphene superlattices. Science 346, 448–451 (2014). The first experimental report of valley Hall effect in graphene with broken inversion symmetry, using an electronic transport measurement.

    Article  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

  28. Mak, K. F., McGill, K. L., Park, J. & McEuen, P. L. The valley Hall effect in MoS2 transistors. Science 344, 1489–1492 (2014). The first experimental report of the valley hall effect in a monolayer TMD using optical injection.

    Article  CAS  Google Scholar 

  29. Lee, J., Mak, K. F. & Shan, J. Electrical control of the valley Hall effect in bilayer MoS2 transistors. Nat. Nanotechnol. 11, 421–425 (2016).

    Article  CAS  Google Scholar 

  30. Yankowitz, M. et al. Emergence of superlattice Dirac points in graphene on hexagonal boron nitride. Nat. Phys. 8, 382–386 (2012).

    Article  CAS  Google Scholar 

  31. Hunt, B. et al. Massive Dirac fermions and Hofstadter butterfly in a van der Waals heterostructure. Science 340, 1427–1430 (2013).

    Article  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

  34. Yu, H., Cui, X., Xu, X. & Yao, W. Valley excitons in two-dimensional semiconductors. Natl Sci. Rev. 2, 57–70 (2015).

    Article  CAS  Google Scholar 

  35. Chernikov, A. et al. Exciton binding energy and nonhydrogenic Rydberg series in monolayer WS2 . Phys. Rev. Lett. 113, 076802 (2014).

    Article  CAS  Google Scholar 

  36. Ye, Z. et al. Probing excitonic dark states in single-layer tungsten disulphide. Nature 513, 214–218 (2014).

    Article  CAS  Google Scholar 

  37. Zhu, B., Chen, X. & Cui, X. Exciton binding energy of monolayer WS2 . Sci. Rep. 5, 9218 (2015).

    Article  CAS  Google Scholar 

  38. He, K. et al. Tightly bound excitons in monolayer WSe2 . Phys. Rev. Lett. 113, 026803 (2014).

    Article  CAS  Google Scholar 

  39. 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).

    Article  CAS  Google Scholar 

  40. Zhang, C., Johnson, A., Hsu, C.-L., Li, L.-J. & Shih, C.-K. Direct imaging of band profile in single layer MoS2 on graphite: quasiparticle energy gap, metallic edge states, and edge band bending. Nano Lett. 14, 2443–2447 (2014).

    Article  CAS  Google Scholar 

  41. Ugeda, M. M. et al. Giant bandgap renormalization and excitonic effects in a monolayer transition metal dichalcogenide semiconductor. Nat. Mater. 13, 1091–1095 (2014).

    Article  CAS  Google Scholar 

  42. Qiu, D. Y., Felipe, H. & Louie, S. G. Optical spectrum of MoS2: many-body effects and diversity of exciton states. Phys. Rev. Lett. 111, 216805 (2013).

    Article  CAS  Google Scholar 

  43. Feng, J., Qian, X., Huang, C.-W. & Li, J. Strain-engineered artificial atom as a broad-spectrum solar energy funnel. Nat. Photonics 6, 866–872 (2012).

    Article  CAS  Google Scholar 

  44. Berkelbach, T. C., Hybertsen, M. S. & Reichman, D. R. Theory of neutral and charged excitons in monolayer transition metal dichalcogenides. Phys. Rev. B 88, 045318 (2013).

    Article  CAS  Google Scholar 

  45. Zhang, C., Wang, H., Chan, W., Manolatou, C. & Rana, F. Absorption of light by excitons and trions in monolayers of metal dichalcogenide MoS2: experiments and theory. Phys. Rev. B 89, 205436 (2014).

    Article  CAS  Google Scholar 

  46. Steinhoff, A., Rö sner, M., Jahnke, F., Wehling, T. O. & Gies, C. Influence of excited carriers on the optical and electronic properties of MoS2 . Nano Lett. 14, 3743–3748 (2014).

    Article  CAS  Google Scholar 

  47. Sie, E. J., Frenzel, A. J., Lee, Y.-H., Kong, J. & Gedik, N. Intervalley biexcitons and many-body effects in monolayer MoS2 . Phys. Rev. B 92, 125417 (2015).

    Article  CAS  Google Scholar 

  48. You, Y. et al. Observation of biexcitons in monolayer WSe2 . Nat. Phys. 11, 477–481 (2015).

    Article  CAS  Google Scholar 

  49. Mai, C. et al. Many-body effects in valleytronics: direct measurement of valley lifetimes in single-layer MoS2 . Nano Lett. 14, 202–206 (2013).

    Article  CAS  Google Scholar 

  50. Shang, J. et al. Observation of excitonic fine structure in a 2D transition-metal dichalcogenide semiconductor. ACS Nano 9, 647–655 (2015).

    Article  CAS  Google Scholar 

  51. Chernikov, A., Ruppert, C., Hill, H. M., Rigosi, A. F. & Heinz, T. F. Population inversion and giant bandgap renormalization in atomically thin WS2 layers. Nat. Photonics 9, 466–470 (2015).

    Article  CAS  Google Scholar 

  52. Carvalho, B. R., Malard, L. M., Alves, J. M., Fantini, C. & Pimenta, M. A. Symmetry-dependent exciton-phonon coupling in 2D and bulk MoS2 observed by resonance raman scattering. Phys. Rev. Lett. 114, 136403 (2015).

    Article  CAS  Google Scholar 

  53. Kaasbjerg, K., Thygesen, K. S. & Jacobsen, K. W. Phonon-limited mobility in n-type single-layer MoS2 from first principles. Phys. Rev. B 85, 115317 (2012).

    Article  CAS  Google Scholar 

  54. Jones, A. M. et al. Excitonic luminescence upconversion in a two-dimensional semiconductor. Nat. Phys. 12, 323–327 (2015).

    Article  CAS  Google Scholar 

  55. Yu, H., Liu, G.-B., Gong, P., Xu, X. & Yao, W. Dirac cones and Dirac saddle points of bright excitons in monolayer transition metal dichalcogenides. Nat. Commun. 5, 3876 (2014).

    Article  CAS  Google Scholar 

  56. 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  CAS  Google Scholar 

  57. Miller, D. A. B. et al. Electric field dependence of optical absorption near the band gap of quantum-well structures. Phys. Rev. B 32, 1043–1060 (1985).

    Article  CAS  Google Scholar 

  58. Dufferwiel, S. et al. Exciton–polaritons in van der Waals heterostructures embedded in tunable microcavities. Nat. Commun. 6 8579 (2015).

    Article  CAS  Google Scholar 

  59. Liu, X. et al. Strong light–matter coupling in two-dimensional atomic crystals. Nat. Photonics 9, 30–34 (2015).

    Article  CAS  Google Scholar 

  60. Palummo, M., Bernardi, M. & Grossman, J. C. Exciton radiative lifetimes in two-dimensional transition metal dichalcogenides. Nano Lett. 15, 2794–2800 (2015).

    Article  CAS  Google Scholar 

  61. Korn, T., Heydrich, S., Hirmer, M., Schmutzler, J. & Schüller, C. Low-temperature photocarrier dynamics in monolayer MoS2 . Appl. Phys. Lett. 99, 102109 (2011).

    Article  CAS  Google Scholar 

  62. Moody, G. et al. Intrinsic homogeneous linewidth and broadening mechanisms of excitons in monolayer transition metal dichalcogenides. Nat. Commun. 6 8315 (2015).

    Article  CAS  Google Scholar 

  63. Amani, M. et al. Near-unity photoluminescence quantum yield in MoS2 . Science 350, 1065–1068 (2015).

    Article  CAS  Google Scholar 

  64. Kumar, N. et al. Exciton–exciton annihilation in MoSe2 monolayers. Phys. Rev. B 89, 125427 (2014).

    Article  CAS  Google Scholar 

  65. Sun, D. et al. Observation of rapid exciton–exciton annihilation in monolayer molybdenum disulfide. Nano Lett. 14, 5625–5629 (2014).

    Article  CAS  Google Scholar 

  66. Mouri, S. et al. Nonlinear photoluminescence in atomically thin layered WSe2 arising from diffusion-assisted exciton–exciton annihilation. Phys. Rev. B 90, 155449 (2014).

    Article  CAS  Google Scholar 

  67. Wang, H. et al. Fast exciton annihilation by capture of electrons or holes by defects via Auger scattering in monolayer metal dichalcogenides. Phys. Rev. B 91, 165411 (2015).

    Article  CAS  Google Scholar 

  68. Schaibley, J. R. et al. Population pulsation resonances of excitons in monolayer MoSe2 with sub-1 μeV linewidths. Phys. Rev. Lett. 114, 137402 (2015).

    Article  CAS  Google Scholar 

  69. Zhang, X.-X., You, Y., Zhao, S. Y. F. & Heinz, T. F. Experimental evidence for dark excitons in monolayer WSe2 . Phys. Rev. Lett. 115, 257403 (2015).

    Article  CAS  Google Scholar 

  70. Hsu, W.-T. et al. Optically initialized robust valley-polarized holes in monolayer WSe2 . Nat. Commun. 6, 8963 (2015).

    Article  CAS  Google Scholar 

  71. Yang, L. et al. Long-lived nanosecond spin relaxation and spin coherence of electrons in monolayer MoS2 and WS2 . Nat. Phys. 11, 830–834 (2015).

    Article  CAS  Google Scholar 

  72. 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).

    Article  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

  74. Wang, Q. et al. Valley carrier dynamics in monolayer molybdenum disulfide from helicity-resolved ultrafast pump–probe spectroscopy. ACS Nano 7, 11087–11093 (2013).

    Article  CAS  Google Scholar 

  75. Dal Conte, S. et al. Ultrafast valley relaxation dynamics in monolayer MoS2 probed by nonequilibrium optical techniques. Phys. Rev. B 92, 235425 (2015).

    Article  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

  77. Yan, T., Qiao, X., Tan, P. & Zhang, X. Exciton valley dynamics in monolayer WSe2 probed by ultrafast Kerr rotation. Preprint at http://arxiv.org/abs/1507.04599 (2015).

  78. Plechinger, G., Nagler, P. & Korn, T. Time-resolved Kerr rotation spectroscopy of valley dynamics in single-layer MoS2. Preprint at https://arxiv.org/abs/1404.7674 (2014).

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

    Article  CAS  Google Scholar 

  80. 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  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

  82. Rivera, P. et al. Valley-polarized exciton dynamics in a 2D semiconductor heterostructure. Science 351, 688–691 (2016). Recent experimental report of interlayer valley-dependent effects in a 2D semiconductor heterostructure.

    Article  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

  84. Rostami, H. & Asgari, R. Valley Zeeman effect and spin-valley polarized conductance in monolayer MoS2 in a perpendicular magnetic field. Phys. Rev. B 91, 075433 (2015).

    Article  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

  86. 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 (2015).

    Article  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

  88. Mitioglu, A. et al. Optical investigation of monolayer and bulk tungsten diselenide (WSe2) in high magnetic fields. Nano Lett. 15, 4387–4392 (2015).

    Article  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

  91. Qi, J., Li, X., Niu, Q. & Feng, J. Giant and tunable valley degeneracy splitting in MoTe2 . Phys. Rev. B 92, 121403 (2015).

    Article  CAS  Google Scholar 

  92. Sie, E. J. et al. Valley-selective optical Stark effect in monolayer WS2 . Nat. Mater. 14, 290–294 (2015).

    Article  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

  94. Geim, A. & Grigorieva, I. Van der Waals heterostructures. Nature 499, 419–425 (2013).

    Article  CAS  Google Scholar 

  95. Ponomarenko, L. A. et al. Cloning of Dirac fermions in graphene superlattices. Nature 497, 594–597 (2013).

    Article  CAS  Google Scholar 

  96. Dean, C. R. et al. Hofstadter's butterfly and the fractal quantum Hall effect in moire superlattices. Nature 497, 598–602 (2013).

    Article  CAS  Google Scholar 

  97. Mishchenko, A. et al. Twist-controlled resonant tunnelling in graphene/boron nitride/graphene heterostructures. Nat. Nanotechnol. 9, 808–813 (2014).

    Article  CAS  Google Scholar 

  98. Lane, T. L., Wallbank, J. R. & Fal'ko, V. I. Twist-controlled resonant tunnelling between monolayer and bilayer graphene. Appl. Phys. Lett. 107, 203506 (2015).

    Article  CAS  Google Scholar 

  99. Terrones, H., López-Urías, F. & Terrones, M. Novel hetero-layered materials with tunable direct band gaps by sandwiching different metal disulfides and diselenides. Sci. Rep. 3, 1549 (2013).

    Article  CAS  Google Scholar 

  100. Kang, J., Tongay, S., Zhou, J., Li, J. & Wu, J. Band offsets and heterostructures of two-dimensional semiconductors. Appl. Phys. Lett. 102, 012111 (2013).

    Article  CAS  Google Scholar 

  101. Kos´mider, K. & Fernández-Rossier, J. Electronic properties of the MoS2–WS2 heterojunction. Phys. Rev. B 87, 075451 (2013).

    Article  CAS  Google Scholar 

  102. Komsa, H.-P. & Krasheninnikov, A. V. Electronic structures and optical properties of realistic transition metal dichalcogenide heterostructures from first principles. Phys. Rev. B 88 085318 (2013).

    Article  CAS  Google Scholar 

  103. Chiu, M.-H. et al. Determination of band alignment in the single-layer MoS2/WSe2 heterojunction. Nat. Commun. 6, 7666 (2015).

    Article  CAS  Google Scholar 

  104. Amin, B. Singh, N. & Schwingenschlögl, U. Heterostructures of transition metal dichalcogenides. Phys. Rev. B 92 075439 (2015).

    Article  CAS  Google Scholar 

  105. Constantinescu, G. C. & Hine, N. D. M. Energy landscape and band-structure tuning in realistic MoS2/MoSe2 heterostructures. Phys. Rev. B 91 195416 (2015).

    Article  CAS  Google Scholar 

  106. Kang, J., Li, J., Li, S. S., Xia, J. B. & Wang, L. W. Electronic structural Moire pattern effects on MoS2/MoSe2 2D heterostructures. Nano Lett. 13, 5485–5490 (2013).

    Article  CAS  Google Scholar 

  107. Rivera, P. et al. Observation of long-lived interlayer excitons in monolayer MoSe2–WSe2 heterostructures. Nat. Commun. 6, 6242 (2015).

    Article  CAS  Google Scholar 

  108. Fang, H. et al. Strong interlayer coupling in van der Waals heterostructures built from single-layer chalcogenides. Proc. Natl Acad. Sci. USA 111, 6198–6202 (2014).

    Article  CAS  Google Scholar 

  109. Chiu, M.-H. et al. Spectroscopic signatures for interlayer coupling in MoS2–WSe2 van der Waals stacking. ACS Nano 8, 9649–9656 (2014).

    Article  CAS  Google Scholar 

  110. Lee, C.-H. et al. Atomically thin p–n junctions with van der Waals heterointerfaces. Nat. Nanotechnol. 9, 676–681 (2014).

    Article  CAS  Google Scholar 

  111. Furchi, M. M., Pospischil, A., Libisch, F., Burgdörfer, J. & Mueller, T. Photovoltaic effect in an electrically tunable van der Waals heterojunction. Nano Lett. 14, 4785–4791 (2014).

    Article  CAS  Google Scholar 

  112. Cheng, R. et al. Electroluminescence and photocurrent generation from atomically sharp WSe2/MoS2 heterojunction p–n diodes. Nano Lett. 14, 5590–5597 (2014).

    Article  CAS  Google Scholar 

  113. Hong, X. et al. Ultrafast charge transfer in atomically thin MoS2/WS2 heterostructures. Nat. Nanotechnol. 9, 682–686 (2014).

    Article  CAS  Google Scholar 

  114. Ceballos, F., Bellus, M. Z., Chiu, H.-Y. & Zhao, H. Ultrafast charge separation and indirect exciton formation in a MoS2–MoSe2 van der Waals heterostructure. ACS Nano 8, 12717–12724 (2014).

    Article  CAS  Google Scholar 

  115. Gong, Y. et al. Vertical and in-plane heterostructures from WS2/MoS2 monolayers. Nat. Mater. 13, 1135–1142 (2014).

    Article  CAS  Google Scholar 

  116. Tongay, S. et al. Tuning interlayer coupling in large-area heterostructures with CVD-grown MoS2 and WS2 monolayers. Nano Lett. 14, 3185–3190 (2014).

    Article  CAS  Google Scholar 

  117. Bellus, M. Z., Ceballos, F., Chiu, H.-Y. & Zhao, H. Tightly bound trions in transition metal dichalcogenide heterostructures. ACS Nano 9, 6459–6464 (2015).

    Article  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

  119. Ceballos, F., Bellus, M. Z., Chiu, H.-Y. & Zhao, H. Probing charge transfer excitons in a MoSe2–WS2 van der Waals heterostructure. Nanoscale 7, 17523–17528 (2015).

    Article  CAS  Google Scholar 

  120. Fogler, M., Butov, L. & Novoselov, K. High-temperature superfluidity with indirect excitons in van der Waals heterostructures. Nat. Commun. 5, 4555 (2014).

    Article  CAS  Google Scholar 

  121. Eisenstein, J. P. & MacDonald, A. H. Bose–Einstein condensation of excitons in bilayer electron systems. Nature 432, 691–694 (2004).

    Article  CAS  Google Scholar 

  122. High, A. A., Novitskaya, E. E., Butov, L. V., Hanson, M. & Gossard, A. C. Control of exciton fluxes in an excitonic integrated circuit. Science 321, 229–231 (2008).

    Article  CAS  Google Scholar 

  123. High, A. A. et al. Spontaneous coherence in a cold exciton gas. Nature 483, 584–588 (2012).

    Article  CAS  Google Scholar 

  124. Yu, H., Wang, Y., Tong, Q., Xu, X. & Yao, W. Anomalous light cones and valley optical selection rules of interlayer excitons in twisted heterobilayers. Phys. Rev. Lett. 115, 187002 (2015).

    Article  CAS  Google Scholar 

  125. Li, Y.-M. et al. Light-induced exciton spin Hall effect in van der Waals heterostructures. Phys. Rev. Lett. 115, 166804 (2015).

    Article  CAS  Google Scholar 

  126. Liu, G.-B., Pang, H., Yao, Y. & Yao, W. Intervalley coupling by quantum dot confinement potentials in monolayer transition metal dichalcogenides. New J. Phys. 16, 105011 (2014).

    Article  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

  131. Kumar, S., Kaczmarczyk, A. & Gerardot, B. D. Strain-induced spatial and spectral isolation of quantum emitters in mono-and bilayer WSe2 . Nano Lett. 15, 7567–7573 (2015).

    Article  CAS  Google Scholar 

  132. Tonndorf, P. et al. Single-photon emission from localized excitons in an atomically thin semiconductor. Optica 2, 347–352 (2015).

    Article  CAS  Google Scholar 

  133. Gammon, D., Snow, E. S., Shanabrook, B. V., Katzer, D. S. & Park, D. Fine structure splitting in the optical spectra of single GaAs quantum dots. Phys. Rev. Lett. 76, 3005–3008 (1996).

    Article  CAS  Google Scholar 

  134. Enyashin, A. N., Bar-sadan, M., Houben, L. & Seifert, G. Line defects in molybdenum disulfide layers. J. Phys. Chem. C 117, 10842–10848 (2013).

    Article  CAS  Google Scholar 

  135. Lin, J., Pantelides, S. T. & Zhou, W. Vacancy-induced formation and growth of inversion domains in transition-metal dichalcogenide monolayer. ACS Nano 9, 5189–5197 (2015).

    Article  CAS  Google Scholar 

  136. Zhou, W. et al. Intrinsic structural defects in monolayer molybdenum disulfide. Nano Lett. 13, 2615–2622 (2013).

    Article  CAS  Google Scholar 

  137. Najmaei, S., Yuan, J., Zhang, J., Ajayan, P. & Lou, J. Synthesis and defect investigation of two-dimensional molybdenum disulfide atomic layers. Acc. Chem. Res. 48, 31–40 (2015).

    Article  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

  139. Zhang, Y. et al. Controlled growth of high quality monolayer WS2 layers on sapphire and imaging its grain boundary. ACS Nano 7, 8963–8971 (2013).

    Article  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

  141. Komsa, H. P. et al. Two-dimensional transition metal dichalcogenides under electron irradiation: defect production and doping. Phys. Rev. Lett. 109, 035503 (2012).

    Article  CAS  Google Scholar 

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

    Article  Google Scholar 

  143. Komsa, H. P., Kurasch, S., Lehtinen, O., Kaiser, U. & Krasheninnikov, A. V. From point to extended defects in two-dimensional MoS2: evolution of atomic structure under electron irradiation. Phys. Rev. B 88, 1–8 (2013).

    Google Scholar 

  144. Komsa, H.-p. et al. Three-fold rotational defects in two-dimensional transition metal dichalcogenides. Nat. Commun. 6, 6736 (2015).

    Article  CAS  Google Scholar 

  145. Yin, Z. et al. Single-layer MoS2 phototransistors. ACS Nano 6, 74–80 (2012).

    Article  Google Scholar 

  146. Lee, H. S. et al. MoS2 nanosheet phototransistors with thickness-modulated optical energy gap. Nano Lett. 12, 3695–3700 (2012).

    Article  CAS  Google Scholar 

  147. Choi, W. et al. High-detectivity multilayer MoS2 phototransistors with spectral response from ultraviolet to infrared. Adv. Mat. 24, 5832–5836 (2012).

    Article  CAS  Google Scholar 

  148. Lopez-Sanchez, O., Lembke, D., Kayci, M., Radenovic, A. & Kis, A. Ultrasensitive photodetectors based on monolayer MoS2 . Nat. Nanotechnol. 8, 497–501 (2013).

    Article  CAS  Google Scholar 

  149. Bernardi, M., Palummo, M. & Grossman, J. C. Extraordinary sunlight absorption and one nanometer thick photovoltaics using two-dimensional monolayer materials. Nano Lett. 13, 3664–3670 (2013).

    Article  CAS  Google Scholar 

  150. Britnell, L. et al. Strong light-matter interactions in heterostructures of atomically thin films. Science 340, 1311–1314 (2013).

    Article  CAS  Google Scholar 

  151. Tsai, M.-L. et al. Monolayer MoS2 heterojunction solar cells. ACS Nano 8, 8317–8322 (2014).

    Article  CAS  Google Scholar 

  152. Sundaram, R. S. et al. Electroluminescence in single layer MoS2 . Nano Lett. 13, 1416–1421 (2013).

    Article  CAS  Google Scholar 

  153. Ye, Y. et al. Exciton-dominant electroluminescence from a diode of monolayer MoS2 . Appl. Phys. Lett. 104, 193508–193508 (2014).

    Article  CAS  Google Scholar 

  154. Lopez-Sanchez, O. et al. Light generation and harvesting in a van der Waals heterostructure. ACS Nano 8, 3042–3048 (2014).

    Article  CAS  Google Scholar 

  155. Ross, J. S. et al. Electrically tunable excitonic light-emitting diodes based on monolayer WSe2 p–n junctions. Nat. Nanotechnol. 9, 268–272 (2014).

    Article  CAS  Google Scholar 

  156. Pospischil, A., Furchi, M. M. & Mueller, T. Solar-energy conversion and light emission in an atomic monolayer p–n diode. Nat. Nanotechnol. 9, 257–261 (2014).

    Article  CAS  Google Scholar 

  157. Baugher, B. W. H., Churchill, H. O. H., Yang, Y. & Jarillo-Herrero, P. Optoelectronic devices based on electrically tunable p–n diodes in a monolayer dichalcogenide. Nat. Nanotechnol. 9, 262–267 (2014).

    Article  CAS  Google Scholar 

  158. Ross, J. S. et al. Electrical control of neutral and charged excitons in a monolayer semiconductor. Nat. Commun. 4, 1484 (2013).

    Article  CAS  Google Scholar 

  159. Withers, F. et al. Light-emitting diodes by band-structure engineering in van der Waals heterostructures. Nat. Mater. 14, 301–306 (2015).

    Article  CAS  Google Scholar 

  160. Wu, S. et al. Monolayer semiconductor nanocavity lasers with ultralow thresholds. Nature 520, 69–72 (2015).

    Article  CAS  Google Scholar 

  161. Ye, Y. et al. Monolayer excitonic laser. Nat. Photonics 9, 733–737 (2015).

    Article  CAS  Google Scholar 

  162. Yang, W. et al. Electrically tunable valley-light emitting diode (vLED) based on CVD-grown monolayer WS2 . Nano Lett. 16, 1560–1567 (2016).

    Article  CAS  Google Scholar 

  163. Kormányos, A. et al. Monolayer MoS2: trigonal warping, the Γ valley, and spin-orbit coupling effects. Phys. Rev. B 88, 045416 (2013).

    Article  CAS  Google Scholar 

  164. 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  CAS  Google Scholar 

  165. Kormányos, A. et al. k·p theory for two-dimensional transition metal dichalcogenide semiconductors. 2D Mater. 2, 022001 (2015).

    Article  CAS  Google Scholar 

  166. Yu, H., Wu, Y., Liu, G.-B., Xu, X. & Yao, W. Nonlinear valley and spin currents from Fermi pocket anisotropy in 2D crystals. Phys. Rev. Lett. 113, 156603 (2014).

    Article  CAS  Google Scholar 

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

    Article  CAS  Google Scholar 

  168. Onga, M., Zhang, Y., Suzuki, R. & Iwasa, Y. High circular polarization in electroluminescence from MoSe2 . Appl. Phys. Lett. 108, 073107 (2016).

    Article  CAS  Google Scholar 

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

    Article  Google Scholar 

  170. Seyler, K. L. et al. Electrical control of second-harmonic generation in a WSe2 monolayer transistor. Nat. Nanotechnol. 10, 407–411 (2015).

    Article  CAS  Google Scholar 

  171. Xiao, J. et al. Nonlinear optical selection rule based on valley-exciton locking in monolayer WS2 . Light Sci. Appl. 4, e366 (2015).

    Article  CAS  Google Scholar 

  172. Muniz, R. A. & Sipe, J. E. All-optical injection of charge, spin, and valley currents in monolayer transition-metal dichalcogenides. Phys. Rev. B 91, 085404 (2015).

    Article  CAS  Google Scholar 

  173. Wang, L. et al. One-dimensional electrical contact to a two-dimensional material. Science 342, 614–617 (2013).

    Article  CAS  Google Scholar 

  174. Xiao, D., Chang, M.-C. & Niu, Q. Berry phase effects on electronic properties. Rev. Mod. Phys. 82, 1959–2007 (2010).

    Article  CAS  Google Scholar 

  175. Mak, K. F. et al. Tightly bound trions in monolayer MoS2 . Nat. Mater. 12, 207–211 (2012).

    Article  CAS  Google Scholar 

  176. Mitioglu, A. A. et al. Optical manipulation of the exciton charge state in single-layer tungsten disulfide. Phys. Rev. B 88, 245403 (2013).

    Article  CAS  Google Scholar 

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Acknowledgements

This work is mainly supported by the Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division (DE-SC0008145 and SC0012509). G.C. and P.R. acknowledge support from NSF-EFRI-1433496 and AFOSR FA9550-14-1-0277. H.Y. and W.Y. were supported by the Croucher Foundation (Croucher Innovation Award), and the Research Grants Council (RGC) and University Grants Committee (UGC) of Hong Kong (HKU17305914P, HKU9/CRF/13G, AoE/P-04/08). X.X. acknowledges a Cottrell Scholar Award, support from the State of Washington funded Clean Energy Institute, and support from Boeing Distinguished Professorship.

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Authors and Affiliations

  1. Department of Physics, University of Washington, Seattle, 98195, Washington, USA

    John R. Schaibley, Pasqual Rivera, Kyle L. Seyler & Xiaodong Xu

  2. Department of Physics and Center of Theoretical and Computational Physics, University of Hong Kong, Hong Kong, China

    Hongyi Yu & Wang Yao

  3. Department of Materials Science and Engineering, University of Washington, Seattle, 98195, Washington, USA

    Genevieve Clark, Jason S. Ross & Xiaodong Xu

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  1. John R. Schaibley
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Schaibley, J., Yu, H., Clark, G. et al. Valleytronics in 2D materials. Nat Rev Mater 1, 16055 (2016). https://doi.org/10.1038/natrevmats.2016.55

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