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.

Directional massless Dirac fermions in a layered van der Waals material with one-dimensional long-range order

Abstract

One or a few layers of van der Waals (vdW) materials are promising for applications in nanoscale electronics. Established properties include high mobility in graphene, a large direct gap in monolayer MoS2, the quantum spin Hall effect in monolayer WTe2 and so on. These exciting properties arise from electron quantum confinement in the two-dimensional limit. Here, we use angle-resolved photoemission spectroscopy to reveal directional massless Dirac fermions due to one-dimensional confinement of carriers in the layered vdW material NbSi0.45Te2. The one-dimensional directional massless Dirac fermions are protected by non-symmorphic symmetry, and emerge from a stripe-like structural modulation with long-range translational symmetry only along the stripe direction as we show using scanning tunnelling microscopy. Our work not only provides a playground for investigating further the properties of directional massless Dirac fermions, but also introduces a unique component with one-dimensional long-range order for engineering nano-electronic devices based on heterostructures of vdW materials.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Fig. 1: Crystal structure and core-level spectra of NbSixTe2.
Fig. 2: Surface electronic structure of NbSi0.45Te2.
Fig. 3: 1D Dirac dispersion on the stripe-like surface of NbSi0.45Te2.
Fig. 4: The non-symmorphic symmetry protected 1D Dirac dispersion with fourfold degeneracy.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.

References

  1. 1.

    Novoselov, K. S. et al. Electric field effect in atomically thin carbon films. Science 306, 666–669 (2004).

    CAS  Google Scholar 

  2. 2.

    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 

  3. 3.

    Lu, J. M. et al. Evidence for two-dimensional Ising superconductivity in gated MoS2. Science 350, 1353–1357 (2015).

    CAS  Article  Google Scholar 

  4. 4.

    Xi, X. X. et al. Ising pairing in superconducting NbSe2 atomic layers. Nat. Phys. 12, 139–143 (2016).

    CAS  Article  Google Scholar 

  5. 5.

    Qian, X. F., Liu, J. W., Fu, L. & Li, J. Quantum spin Hall effect in two-dimensional transition metal dichalcogenides. Science 346, 1344–1347 (2014).

    CAS  Article  Google Scholar 

  6. 6.

    Fei, Z. Y. et al. Edge conduction in monolayer WTe2. Nat. Phys. 13, 677–682 (2017).

    CAS  Article  Google Scholar 

  7. 7.

    Tang, S. J. et al. Quantum spin hall state in monolayer 1T’-WTe2. Nat. Phys. 13, 683–687 (2017).

    CAS  Article  Google Scholar 

  8. 8.

    Wu, S. F. et al. Observation of the quantum spin hall effect up to 100 kelvin in a monolayer crystal. Science 359, 76–79 (2018).

    CAS  Article  Google Scholar 

  9. 9.

    Zhu, Z. et al. Quasiparticle interference and nonsymmorphic effect on a floating band surface state of ZrSiSe. Nat. Commum. 9, 4153 (2018).

    Article  Google Scholar 

  10. 10.

    Gong, C. et al. Discovery of intrinsic ferromagnetism in two-dimensional van der Waals crystals. Nature 546, 265–269 (2017).

    CAS  Article  Google Scholar 

  11. 11.

    Huang, B. et al. Layer-dependent ferromagnetism in a van der Waals crystal down to the monolayer limit. Nature 546, 270–273 (2017).

    CAS  Article  Google Scholar 

  12. 12.

    Cao, Y. et al. Unconventional superconductivity in magic-angle graphene superlattices. Nature 556, 43–50 (2018).

    CAS  Article  Google Scholar 

  13. 13.

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

    CAS  Article  Google Scholar 

  14. 14.

    Young, S. M. & Kane, C. L. Dirac semimetals in two dimensions. Phys. Rev. Lett. 115, 126803 (2015).

    Article  Google Scholar 

  15. 15.

    Bzdušek, T., Wu, Q., Rüegg, A., Sigrist, M. & Soluyanov, A. A. Nodal-chain metals. Nature 538, 75–78 (2016).

    Article  Google Scholar 

  16. 16.

    Wang, Z. et al. Dirac semimetal and topological phase transitions in A3Bi (A = Na, K, Rb). Phys. Rev. B 85, 195320 (2012).

    Google Scholar 

  17. 17.

    Li, J., Badding, M. E. & DiSalvo, F. J. New layered ternary niobium tellurides: synthesis, structure, and properties of niobium metal telluride. NbMTe2 (M = iron, cobalt). Inorg. Chem. 31, 1050–1054 (1992).

    CAS  Article  Google Scholar 

  18. 18.

    Huang, B., Shang, B. & Huang, J. Crystal structure of mixed metal cluster Co2Nb2Te4 obtained by solid state reaction. Jiegou Huaxue (J. Struct. Chem.) 7, 133 (1988).

    CAS  Google Scholar 

  19. 19.

    Huang, B., Shang, B. & Huang, J. Crystal structure of mixed metal cluster Ni2Nb2Te4 obtained by solid state reaction. Jiegou Huaxue (J. Struct. Chem.) 7, 214 (1988).

    CAS  Google Scholar 

  20. 20.

    Huang, B., Shang, B. & Huang, J. Synthesis and crystal structure of a new ternary tantalum chalcogenide Ni2Ta2Te4. Jiegou Huaxue (J. Struct. Chem.) 8, 145 (1989).

    CAS  Google Scholar 

  21. 21.

    Li, J., Badding, M. E. & DiSalvo, F. J. Synthesis and structure of Nb3SiTe6, a new layered ternary niobium telluride compound. J. Alloy. Compd. 184, 257–163 (1992).

    CAS  Article  Google Scholar 

  22. 22.

    Hu, J. et al. Enhanced electron coherence in atomically thin Nb3SiTe6. Nat. Phys. 11, 471–476 (2015).

    CAS  Article  Google Scholar 

  23. 23.

    Li, Si et al. Nonsymmorphic-symmetry-protected hourglass dirac loop, nodal line, and dirac point in bulk and monolayer X3SiTe6 (X = Ta, Nb). Phys. Rev. B 97, 045131 (2018).

    CAS  Article  Google Scholar 

  24. 24.

    Boucher, F., Zhukov, V. & Evain, M. MAxTe2 phases (M = Nb, Ta; A = Si, Ge; 1/3 ≤ x ≤ 1/2): an electronic band structure calculation analysis. Chem. 35, 7649–7654 (1996).

    CAS  Google Scholar 

  25. 25.

    Weber, F. et al. Three-dimensional Fermi surface of 2H-NbSe2: implications for the mechanism of charge density waves. Phys. Rev. B 97, 235122 (2018).

    CAS  Article  Google Scholar 

  26. 26.

    Sato, T. et al. Observation of band crossings protected by nonsymmorphic symmetry in the layered ternary telluride Ta3SiTe6. Phys. Rev. B 98, 121111(R) (2018).

    Article  Google Scholar 

  27. 27.

    Riley, J. M. et al. Direct observation of spin-polarized bulk bands in an inversion-symmetric semiconductor. Nat. Phys. 10, 835–839 (2014).

    CAS  Article  Google Scholar 

  28. 28.

    Pescia, D., Law, A. R., Johnson, M. T. & Hughes, H. P. Determination of observable conduction band symmetry in angle-resolved electron spectroscopies: Non-symmorphic space groups. Solid State Commun. 56, 809–812 (1985).

    CAS  Article  Google Scholar 

  29. 29.

    Finteis, Th et al. Occupied and unoccupied electronic band structure of WSe2. Phys. Rev. B 55, 10400 (1997).

    CAS  Article  Google Scholar 

  30. 30.

    Landolt, G. et al. Bulk and surface rashba splitting in single termination BiTeCl. New J. Phys. 15, 085022 (2013).

    Article  Google Scholar 

  31. 31.

    Koller, G. et al. Intra- and intermolecular band dispersion in an organic crystal. Science 317, 351–355 (2007).

    CAS  Article  Google Scholar 

  32. 32.

    Yin, D., Chen, C., Saito, M., Inoue, K. & Ikuhara, Y. Ceramic phases with one-dimensional long-range order. Nat. Mater. 18, 19–23 (2019).

    CAS  Article  Google Scholar 

  33. 33.

    Liu, Z. K. et al. Discovery of a three-dimensional topological dirac semimetal, Na3Bi. Science 343, 864–867 (2014).

    CAS  Article  Google Scholar 

  34. 34.

    Neupane, M. et al. Observation of a three-dimensional topological dirac semimetal phase in high-mobility Cd3As2. Nat. Commun. 5, 3786 (2014).

    CAS  Article  Google Scholar 

  35. 35.

    Borisenko, S. et al. Experimental realization of a three-dimensional dirac semimetal. Phys. Rev. Lett. 113, 027603 (2014).

    Article  Google Scholar 

  36. 36.

    Schoop, L. M. et al. Dirac cone protected by non-symmorphic symmetry and three-dimensional dirac line node in ZrSiS. Nat. Commun. 7, 11696 (2016).

    CAS  Article  Google Scholar 

  37. 37.

    Ekahana, S. A. et al. Observation of nodal line in non-symmorphic topological semimetal InBi. New J. Phys. 19, 065007 (2017).

    Article  Google Scholar 

  38. 38.

    Schoop, L. M. et al. Tunable weyl and dirac states in the nonsymmorphic compound CeSbTe. Sci. Adv. 4, eaar2317 (2018).

    Article  Google Scholar 

  39. 39.

    Nakayama, K. et al. Band splitting and weyl nodes in trigonal tellurium studied by angle-resolved photoemission spectroscopy and density functional theory. Phys. Rev. B 95, 125204 (2017).

    Article  Google Scholar 

  40. 40.

    Weng, H. et al. Topological node-line semimetal in three-dimensional graphene networks. Phys. Rev. B 92, 045108 (2015).

    Article  Google Scholar 

  41. 41.

    Bian, G. et al. Topological nodal-line fermions in spin-orbit metal PbTaSe2. Nat. Commun. 7, 10556 (2016).

    CAS  Article  Google Scholar 

  42. 42.

    Hu, J. et al. Evidence of topological nodal-line fermions in ZrSiSe and ZrSiTe. Phys. Rev. Lett. 117, 016602 (2016).

    Article  Google Scholar 

Download references

Acknowledgements

This work was supported by the National Key R&D Programme of China (grant nos. 2018FYA0305800, 2016YFA0300403 and 2017YFA0302901), the Ministry of Science and Technology of China (grant no. 2018YFA0307000), the National Natural Science Foundation of China (grant nos. 11874047, 11674226, 11790313 and 11774399), the Fundamental Research Funds for the Central Universities (grant no. 2042018kf-0030), Beijing Natural Science Foundation (grant no. Z180008) and the K. C. Wong Education Foundation (grant no. GJTD-2018-01). Z.Q.M. acknowledges the support by the US Department of Energy under grant no. DE-SC0019068. N.X. acknowledges support by Wuhan University startup funding.

Author information

Affiliations

Authors

Contributions

N.X. conceived the experiments. T.Y.Y, Q.W., C.P. and N.X. performed the ARPES measurements with the assistance of Y.B.H. D.Y.Y and Y.G.S. synthesized the NbSi0.45Te2 single crystals. Z.Z, H.Z. and J.-F.J. performed the STM measurements. Z.W.W, R.Y., S.L., S.A.Y. performed the ab initio calculations. J.H. and Z.Q.M synthesized the NbSi1/3Te2 single crystals as reference samples. T.Y.Y, Q.W., H.Z. and N.X. analysed the experimental data. N.X. wrote the manuscript. All authors discussed the results and commented on the manuscript.

Corresponding author

Correspondence to N. Xu.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Figs. 1–6.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Yang, T.Y., Wan, Q., Yan, D.Y. et al. Directional massless Dirac fermions in a layered van der Waals material with one-dimensional long-range order. Nat. Mater. 19, 27–33 (2020). https://doi.org/10.1038/s41563-019-0494-1

Download citation

Further reading

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing