Advertisement

Nano Research

, Volume 11, Issue 12, pp 6252–6259 | Cite as

Probing magnetic-proximity-effect enlarged valley splitting in monolayer WSe2 by photoluminescence

  • Chenji Zou
  • Chunxiao CongEmail author
  • Jingzhi Shang
  • Chuan Zhao
  • Mustafa Eginligil
  • Lishu Wu
  • Yu Chen
  • Hongbo Zhang
  • Shun Feng
  • Jing Zhang
  • Hao ZengEmail author
  • Wei HuangEmail author
  • Ting YuEmail author
Research Article
  • 131 Downloads

Abstract

Possessing a valley degree of freedom and potential in information processing by manipulating valley features (such as valley splitting), group-VI monolayer transition metal dichalcogenides have attracted enormous interest. This valley splitting can be measured based on the difference between the peak energies of σ+ and σ polarized emissions for excitons or trions in direct band gap monolayer transition metal dichalcogenides under perpendicular magnetic fields. In this work, a well-prepared heterostructure is formed by transferring exfoliated WSe2 onto a EuS substrate. Circular-polarization-resolved photoluminescence spectroscopy, one of the most facile and intuitive methods, is used to probe the difference of the gap energy in two valleys under an applied out-of-plane external magnetic field. Our results indicate that valley splitting can be enhanced when using a EuS substrate, as compared to a SiO2/Si substrate. The enhanced valley splitting of the WSe2/EuS heterostructure can be understood as a result of an interfacial magnetic exchange field originating from the magnetic proximity effect. The value of this magnetic exchange field, based on our estimation, is approximately 9 T. Our findings will stimulate further studies on the magnetic exchange field at the interface of similar heterostructures.

Keywords

valley splitting transition metal dichalcogenides magnetic proximity effect heterostructure magnetic exchange field 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

Notes

Acknowledgements

This work is supported by the National Natural Science Foundation of China (No. 61774040), the National Young 1000 Talent Plan of China, the Shanghai Municipal Natural Science Foundation (No. 16ZR1402500), the Opening project of State Key Laboratory of Functional Materials for Informatics (Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences), Singapore Ministry of Education (MOE) Tier 1 RG199/17, NTU Start-up grant M4080513, US NSF MRI-1229208 and UB RENEW Institute. M. E. acknowledges support by Jiangsu 100 Talent and Six Categories of Talent.

References

  1. [1]
    Radisavljevic, B.; Radenovic, A.; Brivio, J.; Giacometti, V.; Kis, A. Single-layer MoS2 transistors. Nat. Nanotechnol. 2011, 6, 147–150.CrossRefGoogle Scholar
  2. [2]
    Jariwala, D.; Sangwan, V. K.; Lauhon, L. J.; Marks, T. J.; Hersam, M. C. Emerging device applications for semiconducting two-dimensional transition metal dichalcogenides. ACS Nano 2014, 8, 1102–1120.CrossRefGoogle Scholar
  3. [3]
    Wang, Q. H.; Kalantar-Zadeh, K.; Kis, A.; Coleman, J. N.; Strano, M. S. Electronics and optoelectronics of twodimensional transition metal dichalcogenides. Nat. Nanotechnol. 2012, 7, 699–712.CrossRefGoogle Scholar
  4. [4]
    Lopez-Sanchez, O.; Lembke, D.; Kayci, M.; Radenovic, A.; Kis, A. Ultrasensitive photodetectors based on monolayer MoS2. Nat. Nanotechnol. 2013, 8, 497–501.CrossRefGoogle Scholar
  5. [5]
    Xu, X. D.; Yao, W.; Xiao, D.; Heinz, T. F. Spin and pseudospins in layered transition metal dichalcogenides. Nat. Phys. 2014, 10, 343–350.CrossRefGoogle Scholar
  6. [6]
    Peimyoo, N.; Shang, J. Z.; Cong, C. X.; Shen, X. N.; Wu, X. Y.; Yeow, E. K. L.; Yu, T. Nonblinking, intense twodimensional light emitter: Monolayer WS2 triangles. ACS Nano 2013, 7, 10985–10994.CrossRefGoogle Scholar
  7. [7]
    Young, A. F.; Sanchez-Yamagishi, J. D.; Hunt, B.; Choi, S. H.; Watanabe, K.; Taniguchi, T.; Ashoori, R. C.; Jarillo-Herrero, P. Tunable symmetry breaking and helical edge transport in a graphene quantum spin Hall state. Nature 2014, 505, 528–532.CrossRefGoogle Scholar
  8. [8]
    Cai, T. Y.; Yang, S. A.; Li, X.; Zhang, F.; Shi, J. R.; Yao, W.; Niu, Q. Magnetic control of the valley degree of freedom of massive Dirac fermions with application to transition metal dichalcogenides. Phys. Rev. B 2013, 88, 115140.CrossRefGoogle Scholar
  9. [9]
    Wu, S. F.; Ross, J. S.; Liu, G. B.; Aivazian, G.; Jones, A.; Fei, Z. Y.; Zhu, W. G.; Xiao, D.; Yao, W.; Cobden, D. et al. Electrical tuning of valley magnetic moment through symmetry control in bilayer MoS2. Nat. Phys. 2013, 9, 149–153.CrossRefGoogle Scholar
  10. [10]
    Sun, L. F.; Yan, J. X.; Zhan, D.; Liu, L.; Hu, H. L.; Li, H.; Tay, B. K.; Kuo, J. L.; Huang, C. C.; Hewak, D. W. et al. Spin-orbit splitting in single-layer MoS2 revealed by triply resonant Raman scattering. Phys. Rev. Lett. 2013, 111, 126801.CrossRefGoogle Scholar
  11. [11]
    Zeng, H. L.; Dai, J. F.; Yao, W.; Xiao, D.; Cui, X. D. Valley polarization in MoS2 monolayers by optical pumping. Nat. Nanotechnol. 2012, 7, 490–493.CrossRefGoogle Scholar
  12. [12]
    Sie, E. J.; McIver, J.; Lee, Y. H.; Fu, L.; Kong, J.; Gedik, N. Valley-selective optical Stark effect in monolayer WS2. Nat. Mater. 2015, 14, 290–294.CrossRefGoogle Scholar
  13. [13]
    Zeng, H. L.; Cui, X. D. An optical spectroscopic study on two-dimensional group-VI transition metal dichalcogenides. Chem. Soc. Rev. 2015, 44, 2629–2642.CrossRefGoogle Scholar
  14. [14]
    Mak, K. F.; He, K. L.; Shan, J.; Heinz, T. F. Control of valley polarization in monolayer MoS2 by optical helicity. Nat. Nanotechnol. 2012, 7, 494–498.CrossRefGoogle Scholar
  15. [15]
    Yao, W.; Xiao, D.; Niu, Q. Valley-dependent optoelectronics from inversion symmetry breaking. Phys. Rev. B 2008, 77, 235406.CrossRefGoogle Scholar
  16. [16]
    Aivazian, G.; Gong, Z. R.; Jones, A. M.; Chu, R. L.; Yan, J.; Mandrus, D. G.; Zhang, C. W.; Cobden, D.; Yao, W.; Xu, X. Magnetic control of valley pseudospin in monolayer WSe2. Nat. Phys. 2015, 11, 148–152.CrossRefGoogle Scholar
  17. [17]
    MacNeill, D.; Heikes, C.; Mak, K. F.; Anderson, Z.; Kormányos, A.; Zólyomi, V.; Park, J.; Ralph, D. C. Breaking of valley degeneracy by magnetic field in monolayer MoSe2. Phys. Rev. Lett. 2015, 114, 037401.CrossRefGoogle Scholar
  18. [18]
    Li, Y. L.; Ludwig, J.; Low, T.; Chernikov, A.; Cui, X.; Arefe, G.; Kim, Y. D.; van der Zande, A. M.; Rigosi, A.; Hill, H. M. et al. Valley splitting and polarization by the Zeeman effect in monolayer MoSe2. Phys. Rev. Lett. 2014, 113, 266804.CrossRefGoogle Scholar
  19. [19]
    Arora, A.; Schmidt, R.; Schneider, R.; Molas, M. R.; Breslavetz, I.; Potemski, M.; Bratschitsch, R. Valley Zeeman splitting and valley polarization of neutral and charged excitons in monolayer MoTe2 at high magnetic fields. Nano Lett. 2016, 16, 3624–3629.CrossRefGoogle Scholar
  20. [20]
    Mitioglu, A. A.; Plochocka, P.; Granados del Aguila, A.; Christianen, P. C. M.; Deligeorgis, G.; Anghel, S.; Kulyuk, L.; Maude, D. K. Optical investigation of monolayer and bulk tungsten diselenide (WSe2) in high magnetic fields. Nano Lett. 2015, 15, 4387–4392.CrossRefGoogle Scholar
  21. [21]
    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. 2016, 7, 10643.CrossRefGoogle Scholar
  22. [22]
    Wei, P.; Lee, S.; Lemaitre, F.; Pinel, L.; Cutaia, D.; Cha, W.; Katmis, F.; Zhu, Y.; Heiman, D.; Hone, J. et al. Strong interfacial exchange field in the graphene/EuS heterostructure. Nat. Mater. 2016, 15, 711–716.CrossRefGoogle Scholar
  23. [23]
    Zhao, C.; Norden, T.; Zhang, P. Y.; Zhao, P. Q.; Cheng, Y. C.; Sun, F.; Parry, J. P.; Taheri, P.; Wang, J. Q.; Yang, Y. H. et al. Enhanced valley splitting in monolayer WSe2 due to magnetic exchange field. Nat. Nanotechnol. 2017, 12, 757–762.CrossRefGoogle Scholar
  24. [24]
    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. 2012, 108, 196802.CrossRefGoogle Scholar
  25. [25]
    Wang, G.; Bouet, L.; Glazov, M. M.; Amand, T.; Ivchenko, E. L.; Palleau, E.; Marie, X.; Urbaszek, B. Magneto-optics in transition metal diselenide monolayers. 2D Mater. 2015, 2, 034002.CrossRefGoogle Scholar
  26. [26]
    Li, H.; Lu, G.; Wang, Y. L.; Yin, Z. Y.; Cong, C. X.; He, Q. Y.; Wang, L.; Ding, F.; Yu, T.; Zhang, H. Mechanical exfoliation and characterization of single- and few-layer nanosheets of WSe2, TaS2, and TaSe2. Small 2013, 9, 1974–1981.CrossRefGoogle Scholar
  27. [27]
    Sahin, H.; Tongay, S.; Horzum, S.; Fan, W.; Zhou, J.; Li, J.; Wu, J.; Peeters, F. M. Anomalous Raman spectra and thickness-dependent electronic properties of WSe2. Phys. Rev. B 2013, 87, 165409.CrossRefGoogle Scholar
  28. [28]
    Rice, C.; Young, R. J.; Zan, R.; Bangert, U.; Wolverson, D.; Georgiou, T.; Jalil, R.; Novoselov, K. S. Raman-scattering measurements and first-principles calculations of straininduced phonon shifts in monolayer MoS2. Phys. Rev. B 2013, 87, 081307.CrossRefGoogle Scholar
  29. [29]
    Wang, Y. L.; Cong, C. X.; Yang, W. H.; Shang, J. Z.; Peimyoo, N.; Chen, Y.; Kang, J. Y.; Wang, J. P.; Huang, W.; Yu, T. Strain-induced direct–indirect bandgap transition and phonon modulation in monolayer WS2. Nano Res. 2015, 8, 2562–2572.CrossRefGoogle Scholar
  30. [30]
    Liu, Q.; Peng, F. Elasticity and thermodynamic properties of EuS related to phase transition. Chin. J. Chem. Phys. 2014, 27, 387–393.CrossRefGoogle Scholar
  31. [31]
    Morell, N.; Reserbat-Plantey, A.; Tsioutsios, I.; Schadler, K. G.; Dubin, F.; Koppens, F. H.; Bachtold, A. High quality factor mechanical resonators based on WSe2 monolayers. Nano Lett. 2016, 16, 5102–5108.CrossRefGoogle Scholar
  32. [32]
    Tada, H.; Kumpel, A. E.; Lathrop, R. E.; Slanina, J. B.; Nieva, P.; Zavracky, P.; Miaoulis, I. N.; Wong, P. Y. Thermal expansion coefficient of polycrystalline silicon and silicon dioxide thin films at high temperatures. J. Appl. Phys. 2000, 87, 4189–4193.CrossRefGoogle Scholar
  33. [33]
    Chakraborty, B.; Bera, A.; Muthu, D. V. S.; Bhowmick, S.; Waghmare, U. V.; Sood, A. K. Symmetry-dependent phonon renormalization in monolayer MoS2 transistor. Phys. Rev. B 2012, 85, 161403.CrossRefGoogle Scholar
  34. [34]
    Müller, N.; Eckstein, W.; Heiland, W.; Zinn, W. Electron spin polarization in field emission from EuS-coated tungsten tips. Phys. Rev. Lett. 1972, 29, 1651–1654.CrossRefGoogle Scholar
  35. [35]
    Britnell, L.; Ribeiro, R. M.; Eckmann, A.; Jalil, R.; Belle, B. D.; Mishchenko, A.; Kim, Y. J.; Gorbachev, R. V.; Georgiou, T.; Morozov, S. V. et al. Strong light-matter interactions in heterostructures of atomically thin films. Science 2013, 340, 1311–1314.CrossRefGoogle Scholar
  36. [36]
    Tosun, M.; Chuang, S.; Fang, H.; Sachid, A. B.; Hettick, M.; Lin, Y. J.; Zeng, Y. P.; Javey, A. High-gain inverters based on WSe2 complementary field-effect transistors. ACS Nano 2014, 8, 4948–4953.CrossRefGoogle Scholar
  37. [37]
    Srivastava, A.; Sidler, M.; Allain, A. V.; Lembke, D. S.; Kis, A.; Imamoğlu, A. Valley Zeeman effect in elementary optical excitations of monolayer WSe2. Nat. Phys. 2015, 11, 141–147.CrossRefGoogle Scholar
  38. [38]
    Jones, A. M.; Yu, H. Y.; Ghimire, N. J.; Wu, S. F.; Aivazian, G.; Ross, J. S.; Zhao, B.; Yan, J. Q.; Mandrus, D. G.; Xiao, D. et al. Optical generation of excitonic valley coherence in monolayer WSe2. Nat. Nanotechnol. 2013, 8, 634–638.CrossRefGoogle Scholar
  39. [39]
    Huang, J.; Hoang, T. B.; Mikkelsen, M. H. Probing the origin of excitonic states in monolayer WSe2. Sci. Rep. 2016, 6, 22414.CrossRefGoogle Scholar
  40. [40]
    You, Y. M.; Zhang, X.-X.; Berkelbach, T. C.; Hybertsen, M. S.; Reichman, D. R.; Heinz, T. F. Observation of biexcitons in monolayer WSe2. Nat. Phys. 2015, 11, 477–481.CrossRefGoogle Scholar
  41. [41]
    Desai, S. B.; Seol, G.; Kang, J. S.; Fang, H.; Battaglia, C.; Kapadia, R.; Ager, J. W.; Guo, J.; Javey, A. Strain-induced indirect to direct bandgap transition in multilayer WSe2. Nano Lett. 2014, 14, 4592–4597.CrossRefGoogle Scholar
  42. [42]
    Yun, W. S.; Han, S. W.; Hong, S. C.; Kim, I. G.; Lee, J. D. Thickness and strain effects on electronic structures of transition metal dichalcogenides: 2H-MX2 semiconductors (M = Mo, W; X = S, Se, Te). Phys. Rev. B 2012, 85, 033305.CrossRefGoogle Scholar

Copyright information

© Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Shaanxi Institute of Flexible Electronics (SIFE)Northwestern Polytechnical University (NPU)Xi’anChina
  2. 2.Division of Physics and Applied Physics, School of Physical and Mathematical SciencesNanyang Technological UniversitySingaporeSingapore
  3. 3.State Key Laboratory of ASIC & System, School of Information Science and TechnologyFudan UniversityShanghaiChina
  4. 4.Department of PhysicsUniversity at Buffalo, State University of New YorkBuffaloUSA
  5. 5.Key Laboratory of Flexible Electronics (KLOFE) & Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Centre for Advanced Materials (SICAM)Nanjing Tech University (NanjingTech)NanjingChina

Personalised recommendations