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Ultrafast dynamics in van der Waals heterostructures

Abstract

Van der Waals heterostructures are synthetic quantum materials composed of stacks of atomically thin two-dimensional (2D) layers. Because the electrons in the atomically thin 2D layers are exposed to layer-to-layer coupling, the properties of van der Waals heterostructures are defined not only by the constituent monolayers, but also by the interactions between the layers. Many fascinating electrical, optical and magnetic properties have recently been reported in different types of van der Waals heterostructures. In this Review, we focus on unique excited-state dynamics in transition metal dichalcogenide (TMDC) heterostructures. TMDC monolayers are the most widely studied 2D semiconductors, featuring prominent exciton states and accessibility to the valley degree of freedom. Many TMDC heterostructures are characterized by a staggered band alignment. This band alignment has profound effects on the evolution of the excited states in heterostructures, including ultrafast charge transfer between the layers, the formation of interlayer excitons, and the existence of long-lived spin and valley polarization in resident carriers. Here we review recent experimental and theoretical efforts to elucidate electron dynamics in TMDC heterostructures, extending from timescales of femtoseconds to microseconds, and comment on the relevance of these effects for potential applications in optoelectronic, valleytronic and spintronic devices.

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References

  1. 1.

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

  2. 2.

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

  3. 3.

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

  4. 4.

    Spanton, E. M. et al. Observation of fractional Chern insulators in a van der Waals heterostructure. Science 360, 62–66 (2018).

  5. 5.

    Cao, Y. et al. Unconventional superconductivity in magic-angle graphene superlattices. Nature 556, 43 (2018).

  6. 6.

    Cao, Y. et al. Correlated insulator behaviour at half-filling in magic-angle graphene superlattices. Nature 556, 80–84 (2018).

  7. 7.

    Chen, G. et al. Gate-tunable Mott insulator in trilayer graphene–boron nitride moiré superlattice. Preprint at https://arxiv.org/abs/1803.01985 (2018).

  8. 8.

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

  9. 9.

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

  10. 10.

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

  11. 11.

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

  12. 12.

    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).

  13. 13.

    Gong, C. et al. Band alignment of two-dimensional transition metal dichalcogenides: application in tunnel field effect transistors. Appl. Phys. Lett. 103, 053513 (2013).

  14. 14.

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

  15. 15.

    Stormer, H. L., Dingle, R., Gossard, A. C., Wiegmann, W. & Sturge, M. D. 2-dimensional electron-gas at a semiconductor–semiconductor interface. Solid State Commun. 29, 705–709 (1979).

  16. 16.

    Bellus, M. Z. et al. Type-I van der Waals heterostructure formed by MoS2 and ReS2 monolayers. Nanoscale Horiz. 2, 31–36 (2017).

  17. 17.

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

  18. 18.

    Ozcelik, V. O., Azadani, J. G., Yang, C., Koester, S. J. & Low, T. Band alignment of two-dimensional semiconductors for designing heterostructures with momentum space matching. Phys. Rev. B 94, 035125 (2016).

  19. 19.

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

  20. 20.

    Wang, K. et al. Interlayer coupling in twisted WSe2/WS2 bilayer heterostructures revealed by optical spectroscopy. ACS Nano 10, 6612–6622 (2016).

  21. 21.

    Kozawa, D. et al. Evidence for fast interlayer energy transfer in MoSe2/WS2 heterostructures. Nano Lett. 16, 4087–4093 (2016).

  22. 22.

    Zhang, C. X. et al. Systematic study of electronic structure and band alignment of monolayer transition metal dichalcogenides in Van der Waals heterostructures. 2D Mater. 4, 015026 (2017).

  23. 23.

    Debbichi, L., Eriksson, O. & Lebegue, S. Electronic structure of two-dimensional transition metal dichalcogenide bilayers from ab initio theory. Phys. Rev. B 89, 205311 (2014).

  24. 24.

    Zhang, J. F., Xie, W. Y., Zhao, J. J. & Zhang, S. B. Band alignment of two-dimensional lateral heterostructures. 2D Mater. 4, 015038 (2017).

  25. 25.

    Qiu, D. Y., da Jornada, F. H. & Louie, S. G. Screening and many-body effects in two-dimensional crystals: monolayer MoS2. Phys. Rev. B 93, 235435 (2016).

  26. 26.

    Wilson, N. R. et al. Determination of band offsets, hybridization, and exciton binding in 2D semiconductor heterostructures. Sci. Adv. 3, e1601832 (2017).

  27. 27.

    Hill, H. M., Rigosi, A. F., Rim, K. T., Flynn, G. W. & Heinz, T. F. Band alignment in MoS2/WS2 transition metal dichalcogenide heterostructures probed by scanning tunneling microscopy and spectroscopy. Nano Lett. 16, 4831–4837 (2016).

  28. 28.

    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).

  29. 29.

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

  30. 30.

    Zhu, H. M. et al. Interfacial charge transfer circumventing momentum mismatch at two-dimensional van der Waals heterojunctions. Nano Lett. 17, 3591–3598 (2017).

  31. 31.

    Ji, Z. H. et al. Robust stacking-independent ultrafast charge transfer in MoS2/WS2 bilayers. ACS Nano 11, 12020–12026 (2017).

  32. 32.

    Chen, H. L. et al. Ultrafast formation of interlayer hot excitons in atomically thin MoS2/WS2 heterostructures. Nat. Commun. 7, 12512 (2016).

  33. 33.

    Ceballos, F., Ju, M. G., Lane, S. D., Zeng, X. C. & Zhao, H. Highly efficient and anomalous charge transfer in van der Waals trilayer semiconductors. Nano Lett. 17, 1623–1628 (2017).

  34. 34.

    Pan, S. D., Ceballos, F., Bellus, M. Z., Zereshki, P. & Zhao, H. Ultrafast charge transfer between MoTe2 and MoS2 monolayers. 2D Mater. 4, 015033 (2017).

  35. 35.

    Xu, W. G. et al. Correlated fluorescence blinking in two-dimensional semiconductor heterostructures. Nature 541, 62–67 (2017).

  36. 36.

    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).

  37. 37.

    Li, Y. Y. et al. Ultrafast interlayer electron transfer in incommensurate transition metal dichalcogenide homobilayers. Nano Lett. 17, 6661–6666 (2017).

  38. 38.

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

  39. 39.

    Rigosi, A. F., Hill, H. M., Li, Y. L., Chernikov, A. & Heinz, T. F. Probing interlayer interactions in transition metal dichalcogenide heterostructures by optical spectroscopy: MoS2/WS2 and MoSe2/WSe2. Nano Lett. 15, 5033–5038 (2015).

  40. 40.

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

  41. 41.

    Robert, C. et al. Exciton radiative lifetime in transition metal dichalcogenide monolayers. Phys. Rev. B 93, 205423 (2016).

  42. 42.

    Xu, W. S. et al. Determining the optimized interlayer separation distance in vertical stacked 2D WS2:hBN:MoS2 heterostructures for exciton energy transfer. Small 14, 1703727 (2018).

  43. 43.

    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).

  44. 44.

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

  45. 45.

    Zhu, X. Y. et al. Charge transfer excitons at van der Waals interfaces. J. Am. Chem. Soc. 137, 8313–8320 (2015).

  46. 46.

    Wang, H. et al. The role of collective motion in the ultrafast charge transfer in van der Waals heterostructures. Nat. Commun. 7, 11504 (2016).

  47. 47.

    Zhang, J. et al. Interlayer-state-coupling dependent ultrafast charge transfer in MoS2/WS2 bilayers. Adv. Sci. 4, 1700086 (2017).

  48. 48.

    Long, R. & Prezhdo, O. V. Quantum coherence facilitates efficient charge separation at a MoS2/MoSe2 van der Waals junction. Nano Lett. 16, 1996–2003 (2016).

  49. 49.

    Li, L. Q., Long, R. & Prezhdo, O. V. Charge separation and recombination in two-dimensional MoS2/WS2: time-domain ab initio modeling. Chem. Mater. 29, 2466–2473 (2017).

  50. 50.

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

  51. 51.

    Tong, Q. J. et al. Topological mosaics in moiré superlattices of van der Waals heterobilayers. Nat. Phys. 13, 356–362 (2017).

  52. 52.

    Wang, Y., Wang, Z., Yao, W., Liu, G. B. & Yu, H. Y. Interlayer coupling in commensurate and incommensurate bilayer structures of transition-metal dichalcogenides. Phys. Rev. B 95, 115429 (2017).

  53. 53.

    Zheng, Q. J. et al. Phonon-assisted ultrafast charge transfer at van der Waals heterostructure interface. Nano Lett. 17, 6435–6442 (2017).

  54. 54.

    Jin, C. H. et al. On optical dipole moment and radiative recombination lifetime of excitons in WSe2. Adv. Funct. Mater. 27, 1601741 (2017).

  55. 55.

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

  56. 56.

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

  57. 57.

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

  58. 58.

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

  59. 59.

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

  60. 60.

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

  61. 61.

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

  62. 62.

    Mai, C. et al. Many-body effects in valleytronics: direct measurement of valley lifetimes in single-layer MoS2. Nano Lett. 14, 202–206 (2014).

  63. 63.

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

  64. 64.

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

  65. 65.

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

  66. 66.

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

  67. 67.

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

  68. 68.

    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).

  69. 69.

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

  70. 70.

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

  71. 71.

    Hao, K. et al. Trion valley coherence in monolayer semiconductors. 2D Mater. 4, 025105 (2017).

  72. 72.

    Volmer, F. et al. Intervalley dark trion states with spin lifetimes of 150 ns in WSe2. Phys. Rev. B 95, 235408 (2017).

  73. 73.

    Plechinger, G. et al. Trion fine structure and coupled spin–valley dynamics in monolayer tungsten disulfide. Nat. Commun. 7, 12715 (2016).

  74. 74.

    Zhang, X. X. et al. Magnetic brightening and control of dark excitons in monolayer WSe2. Nat. Nanotech. 12, 883–888 (2017).

  75. 75.

    Jiang, C. Y. et al. Microsecond dark-exciton valley polarization memory in two-dimensional heterostructures. Nat. Commun. 9, 753 (2018).

  76. 76.

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

  77. 77.

    Chen, S., Goldstein, T., Taniguchi, T., Watanabe, K. & Yan, J. Coulomb-bound four- and five-particle valleytronic states in an atomically-thin semiconductor. Nat. Commun. 9, 3717 (2018).

  78. 78.

    Dey, P. et al. Gate-controlled spin–valley locking of resident carriers in WSe2 monolayers. Phys. Rev. Lett. 119, 137401 (2017).

  79. 79.

    Song, X. L., Xie, S. E., Kang, K., Park, J. & Sih, V. Long-lived hole spin/valley polarization probed by Kerr rotation in monolayer WSe2. Nano Lett. 16, 5010–5014 (2016).

  80. 80.

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

  81. 81.

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

  82. 82.

    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).

  83. 83.

    Nagler, P. et al. Interlayer exciton dynamics in a dichalcogenide monolayer heterostructure. 2D Mater. 4, 025112 (2017).

  84. 84.

    Rivera, P. et al. Valley-polarized exciton dynamics in a 2D semiconductor heterostructure. Science 351, 688–691 (2016).

  85. 85.

    Hsu, W. T. et al. Negative circular polarization emissions from WSe2/MoSe2 commensurate heterobilayers. Nat. Commun. 9, 1356 (2018).

  86. 86.

    Hanbicki, A. T. et al. Double indirect interlayer exciton in a MoSe2/WSe2 van der Waals heterostructure. ACS Nano 12, 4719 (2018).

  87. 87.

    Ciarrocchi, A. et al. Control of interlayer excitons in two-dimensional van der Waals heterostructures. Preprint at https://arxiv.org/abs/1803.06405 (2018).

  88. 88.

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

  89. 89.

    Yu, H. Y., Liu, B. L. & Yao, W. Brightened spin-triplet interlayer excitons and optical selection rules in van der Waals heterobilayers. 2D Mater. 5, 035021 (2018).

  90. 90.

    Miller, B. et al. Long-lived direct and indirect interlayer excitons in van der Waals heterostructures. Nano Lett. 17, 5229–5237 (2017).

  91. 91.

    Kunstmann, J. et al. Momentum-space indirect interlayer excitons in transition-metal dichalcogenide van der Waals heterostructures. Nat. Phys. 14, 801–805 (2018).

  92. 92.

    Wu, F. C., Lovorn, T. & MacDonald, A. H. Theory of optical absorption by interlayer excitons in transition metal dichalcogenide heterobilayers. Phys. Rev. B 97, 035306 (2018).

  93. 93.

    Yu, H. Y., Liu, G. B., Tang, J. J., Xu, X. D. & Yao, W. Moiré excitons: from programmable quantum emitter arrays to spin–orbit-coupled artificial lattices. Sci. Adv. 3, e1701696 (2017).

  94. 94.

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

  95. 95.

    Jin, C. H. et al. Imaging of pure spin–valley diffusion current in WS2/WSe2 heterostructures. Science 360, 893–896 (2018).

  96. 96.

    Carvalho, B. R. et al. Intervalley scattering by acoustic phonons in two-dimensional MoS2 revealed by double-resonance Raman spectroscopy. Nat. Commun. 8, 14670 (2017).

  97. 97.

    Hill, H. M. et al. Observation of excitonic Rydberg states in monolayer MoS2 and WS2 by photoluminescence excitation spectroscopy. Nano Lett. 15, 2992–2997 (2015).

  98. 98.

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

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Acknowledgements

E.Y.M. acknowledges support from the US Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division, under contract DE-AC02-76SF00515. T.F.H. acknowledges support from the AMOS programme, Chemical Sciences, Geosciences, and Biosciences Division, Basic Energy Sciences, US Department of Energy under contract DE-AC02-76-SF00515 and from the Betty and Gordon Moore Foundation’s EPiQS Initiative through grant no. GBMF4545. O.K. acknowledges the support of the Rothschild Fellowship of Yad Hanadiv Fund, Israel, the Viterbi Fellowship of the Andrew and Erna Viterbi Department of Electrical Engineering, Technion, Israel, and the Betty and Gordon Moore Foundation’s EPiQS Initiative through grant no. GBMF4545. F.W. and E.C.R. acknowledge support from the Director, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division of the US Department of Energy under contract no. DE-AC02-05-CH11231 (van der Waals heterostructures programme, KCWF16). C.J. acknowledges support from the National Science Foundation EFRI programme (EFMA-1542741). E.C.R acknowledges support from the Department of Defense through the National Defense Science & Engineering Graduate (NDSEG) Fellowship programme.

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Correspondence to Feng Wang or Tony F. Heinz.

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Further reading

Fig. 1: Band alignment in vertical vdW heterostructures of TMDCs.
Fig. 2: Experimental studies of ultrafast charge transfer in vertical TMDC heterostructures.
Fig. 3: Theoretical concepts explaining the robust and ultrafast nature of charge transfer in TMDC heterostructures52.
Fig. 4: Dynamics of spin–valley information carriers in TMDC materials.
Fig. 5: Potential origin of intervalley scattering in WSe2/MoS2 heterostructures.
Fig. 6: Spin–valley transport in a vdW heterostructure.