Josephson coupled Ising pairing induced in suspended MoS2 bilayers by double-side ionic gating

Article metrics

Abstract

Superconductivity in monolayer transition metal dichalcogenides is characterized by Ising-type pairing induced via a strong Zeeman-type spin–orbit coupling. When two transition metal dichalcogenides layers are coupled, more exotic superconducting phases emerge, which depend on the ratio of Ising-type protection and interlayer coupling strength. Here, we induce superconductivity in suspended MoS2 bilayers and unveil a coupled superconducting state with strong Ising-type spin–orbit coupling. Gating the bilayer symmetrically from both sides by ionic liquid gating varies the interlayer interaction and accesses electronic states with broken local inversion symmetry while maintaining the global inversion symmetry. We observe a strong suppression of the Ising protection that evidences a coupled superconducting state. The symmetric gating scheme not only induces superconductivity in both atomic sheets but also controls the Josephson coupling between the layers, which gives rise to a dimensional crossover in the bilayer.

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 and device structure of suspended MoS2 bilayer.
Fig. 2: Superconducting phase diagram.
Fig. 3: Upper critical field measurements for single- and double-side gating on a bilayer MoS2.
Fig. 4: The IV mapping of the double-side gated bilayer MoS2.
Fig. 5: The interplay between SOC and interlayer interaction in superconductors with large in-plane Bc2.

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.

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

  2. 2.

    Xi, X. et al. Ising pairing in superconducting NbSe2 atomic layers. Nat. Phys. 12, 139–143 (2015).

  3. 3.

    Saito, Y. et al. Superconductivity protected by spin–valley locking in ion-gated MoS2. Nat. Phys. 12, 144–149 (2015).

  4. 4.

    Lu, J. et al. Full superconducting dome of strong Ising protection in gated monolayer WS2. Proc. Natl Acad. Sci. USA 115, 3551–3556 (2018).

  5. 5.

    de la Barrera, S. C. et al. Tuning Ising superconductivity with layer and spin–orbit coupling in two-dimensional transition-metal dichalcogenides. Nat. Commun. 9, 1427 (2018).

  6. 6.

    Nakosai, S., Tanaka, Y. & Nagaosa, N. Topological superconductivity in bilayer Rashba system. Phys. Rev. Lett. 108, 147003 (2012).

  7. 7.

    Liu, C.-X. Unconventional superconductivity in bilayer transition metal dichalcogenides. Phys. Rev. Lett. 118, 087001 (2017).

  8. 8.

    Nakamura, Y. & Yanase, Y. Odd-parity superconductivity in bilayer transition metal dichalcogenides. Phys. Rev. B. 96, 054501 (2017).

  9. 9.

    Mizukami, Y. et al. Extremely strong-coupling superconductivity in artificial two-dimensional Kondo lattices. Nat. Phys. 7, 849–853 (2011).

  10. 10.

    Liu, Y. et al. Interface-induced zeeman-protected superconductivity in ultrathin crystalline lead films. Phys. Rev. X 8, 021002 (2018).

  11. 11.

    Zhang, X., Liu, Q., Luo, J.-W., Freeman, A. J. & Zunger, A. Hidden spin polarization in inversion-symmetric bulk crystals. Nat. Phys. 10, 387–393 (2014).

  12. 12.

    Tombros, N. et al. Large yield production of high mobility freely suspended graphene electronic devices on a polydimethylglutarimide based organic polymer. J. Appl. Phys. 109, 093702 (2011).

  13. 13.

    Wang, F. et al. Ionic liquid gating of suspended MoS2 field-effect transistor devices. Nano Lett. 15, 5284–5288 (2015).

  14. 14.

    Ye, J. T. et al. Superconducting dome in a gate-tuned band insulator. Science 338, 1193–1196 (2012).

  15. 15.

    Eknapakul, T. et al. Electronic structure of a Quasi-freestanding MoS2 monolayer. Nano Lett. 14, 1312–1316 (2014).

  16. 16.

    Kim, B. S., Rhim, J.-W., Kim, B., Kim, C. & Park, S. R. Determination of the band parameters of bulk 2H-MX2 (M = Mo, W; X = S, Se) by angle-resolved photoemission spectroscopy. Sci. Rep. 6, 36389 (2016).

  17. 17.

    Brumme, T., Calandra, M. & Mauri, F. First-principles theory of field-effect doping in transition-metal dichalcogenides: Structural properties, electronic structure, Hall coefficient, and electrical conductivity. Phys. Rev. B. 91, 155436 (2015).

  18. 18.

    Ovchinnikov, D. et al. Disorder engineering and conductivity dome in ReS2 with electrolyte gating. Nat. Commun. 7, 12391 (2016).

  19. 19.

    Coleman, R. V., Eiserman, G. K., Hillenius, S. J., Mitchell, A. T. & Vicent, J. L. Dimensional crossover in the superconducting intercalated layer compound 2H-TaS2. Phys. Rev. B. 27, 125–139 (1983).

  20. 20.

    Yang, Y. et al. Enhanced superconductivity upon weakening of charge density wave transport in 2H-TaS2 in the two-dimensional limit. Phys. Rev. B. 98, 035203 (2018).

  21. 21.

    Klemm, R. A., Luther, A. & Beasley, M. R. Theory of the upper critical field in layered superconductors. Phys. Rev. B. 12, 877–891 (1975).

  22. 22.

    Klemm, R. A. Layered Superconductors Volume 1 International Series of Monographs on Physics, Vol. 153 (Oxford Univ. Press, 2011).

  23. 23.

    Xia, Y., Xie, W., Ruden, P. P. & Frisbie, C. D. Carrier localization on surfaces of organic semiconductors gated with electrolytes. Phys. Rev. Lett. 105, 036802 (2010).

  24. 24.

    Talantsev, E. F. et al. On the origin of critical temperature enhancement in atomically thin superconductors. 2D Mater. 4, 025072 (2017).

  25. 25.

    Inosov, D. S. et al. Crossover from weak to strong pairing in unconventional superconductors. Phys. Rev. B. 83, 214520 (2011).

  26. 26.

    Devarakonda, A. et al. Evidence for clean 2D superconductivity and field-induced finite-momentum pairing in a bulk vdW superlattice. Preprint at https://arxiv.org/abs/1906.02065 (2019).

  27. 27.

    Ma, Y. et al. Unusual evolution of B c2 and T c with inclined fields in restacked TaS2 nanosheets. NPJ Quantum Mater. 3, 34 (2018).

  28. 28.

    Goh, S. K. et al. Anomalous upper critical field in CeCoIn5/YbCoIn5 superlattices with a Rashba-type heavy Fermion interface. Phys. Rev. Lett. 109, 157006 (2012).

  29. 29.

    Sekihara, T., Masutomi, R. & Okamoto, T. Two-dimensional superconducting state of monolayer Pb films grown on GaAs(110) in a strong parallel magnetic field. Phys. Rev. Lett. 111, 057005 (2013).

  30. 30.

    Woollam, J. A. & Somoano, R. B. Superconducting critical fields of alkali and alkaline-earth intercalates of MoS2. Phys. Rev. B. 13, 3843–3853 (1976).

Download references

Acknowledgements

J.T.Y. acknowledges funding from the European Research Council (consolidator grant no. 648855, Ig-QPD). We acknowledge D.-H. Xu for a fruitful discussion on the KLB model.

Author information

O.Z., J.M.L. and J.T.Y. designed the experiment. O.Z. and J.M.L. fabricated the device and performed the measurements. O.Z., J.M.L., Q.H.C., A.A.E.Y., S.G. and J.T.Y analysed and discussed the data. O.Z. and J.T.Y. wrote the manuscript.

Correspondence to J. T. Ye.

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, Tables 1–4 and refs. 1–11.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Zheliuk, O., Lu, J.M., Chen, Q.H. et al. Josephson coupled Ising pairing induced in suspended MoS2 bilayers by double-side ionic gating. Nat. Nanotechnol. 14, 1123–1128 (2019) doi:10.1038/s41565-019-0564-1

Download citation