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.

  • Letter
  • Published:

Surface-dominated conduction up to 240 K in the Kondo insulator SmB6 under strain

Nature Materials volume 16, pages 708–711 (2017)Cite this article

Subjects

Abstract

SmB6 is a strongly correlated mixed-valence Kondo insulator1,2 with a newly discovered surface state3,4, proposed to be of non-trivial topological origin5,6. However, the surface state dominates electrical conduction only below T∗ ≈ 4 K (ref. 3), limiting its scientific investigation and device application. Here, we report the enhancement of T∗ in SmB6 under the application of tensile strain. With 0.7% tensile strain we report surface-dominated conduction at up to a temperature of 240 K, persisting even after the strain has been removed. This can be explained in the framework of strain-tuned temporal and spatial fluctuations of f-electron configurations, which might be generally applied to other mixed-valence materials. We note that this amount of strain can be induced in epitaxial SmB6 films via substrate in potential device applications.

This is a preview of subscription content, access via your institution

Access options

Buy this article

  • Purchase on Springer Link
  • Instant access to full article PDF
Buy now

Prices may be subject to local taxes which are calculated during checkout

Figure 1: Experimental set-up and gap enhancement with tensile strain in sample A.
Figure 2: Hysteresis and room-temperature surface-dominated conduction.
Figure 3: Temperature–strain phase diagram.

Similar content being viewed by others

References

  1. Fisk, Z. et al. Kondo insulators. Physica B 223, 409–412 (1996).

    Article  Google Scholar 

  2. Riseborough, P. S. Heavy fermion semiconductors. Adv. Phys. 49, 257–320 (2000).

    Article  CAS  Google Scholar 

  3. Kim, D. J. et al. Surface Hall effect and nonlocal transport in SmB6: evidence for surface conduction. Sci. Rep. 3, 3150 (2013).

    Article  CAS  Google Scholar 

  4. Wolgast, S. et al. Low-temperature surface conduction in the Kondo insulator SmB6 . Phys. Rev. B 88, 180405 (2013).

    Article  Google Scholar 

  5. Dzero, M., Sun, K., Coleman, P. & Galitski, V. Theory of topological Kondo insulators. Phys. Rev. B 85, 045130 (2012).

    Article  Google Scholar 

  6. Alexandrov, V., Dzero, M. & Coleman, P. Cubic topological Kondo insulators. Phys. Rev. Lett. 111, 226403 (2013).

    Article  Google Scholar 

  7. Li, G. et al. Two-dimensional Fermi surfaces in Kondo insulator SmB6 . Science 346, 1208–1212 (2014).

    Article  CAS  Google Scholar 

  8. Dzero, M., Sun, K., Galitski, V. & Coleman, P. Topological Kondo insulators. Phys. Rev. Lett. 104, 106408 (2010).

    Article  Google Scholar 

  9. Stern, A., Efimkin, D. K., Galitski, V., Fisk, Z. & Xia, J. Radio frequency tunable oscillator device based on a SmB6 microcrystal. Phys. Rev. Lett. 116, 166603 (2016).

    Article  Google Scholar 

  10. Choi, K. et al. Enhancement of ferroelectricity in strained BaTiO3 thin films. Science 306, 1005–1009 (2004).

    Article  CAS  Google Scholar 

  11. Cooley, J. C., Aronson, M. C., Fisk, Z. & Canfield, P. C. SmB6: Kondo insulator or exotic metal? Phys. Rev. Lett. 74, 1629–1632 (1995).

    Article  CAS  Google Scholar 

  12. Derr, J. et al. From unconventional insulating behavior towards conventional magnetism in the intermediate-valence compound SmB6 . Phys. Rev. B 77, 193107 (2008).

    Article  Google Scholar 

  13. Hicks, C. W., Barber, M. E., Edkins, S. D., Brodsky, D. O. & Mackenzie, A. P. Piezoelectric-based apparatus for strain tuning. Rev. Sci. Instrum. 85, 065003 (2014).

    Article  Google Scholar 

  14. Hicks, C. W. et al. Strong increase of Tc of Sr2RuO4 under both tensile and compressive strain. Science 344, 283–285 (2014).

    Article  CAS  Google Scholar 

  15. Goldstein, R. V., Gorodtsov, V. A. & Lisovenko, D. S. Relation of Poisson’s ratio on average with Young’s modulus. Auxetics on average. Dokl. Phys. 57, 174–178 (2012).

    Article  CAS  Google Scholar 

  16. Tamaki, T. et al. Elastic properties of SmB6 and Sm3Se4 . J. Magn. Magn. Mater. 47, 469–471 (1985).

    Article  Google Scholar 

  17. Beille, J., Maple, M. B., Wittig, J., Fisk, Z. & DeLong, L. E. Suppression of the energy gap in SmB6 under pressure. Phys. Rev. B 28, 7397–7400 (1983).

    Article  CAS  Google Scholar 

  18. Moshchalkov, V. V. et al. SmB6 at high pressures: the transition from insulating to the metallic Kondo lattice. J. Magn. Magn. Mater. 47, 289–291 (1985).

    Article  Google Scholar 

  19. Ren, Z., Taskin, A. A., Sasaki, S., Segawa, K. & Ando, Y. Large bulk resistivity and surface quantum oscillations in the topological insulator Bi2Te2Se. Phys. Rev. B 82, 241306 (2010).

    Article  Google Scholar 

  20. He, L. et al. Surface-dominated conduction in a 6 nm thick Bi2Se3 thin film. Nano Lett. 12, 1486–1490 (2012).

    Article  CAS  Google Scholar 

  21. Mizumaki, M., Tsutsui, S. & Iga, F. Temperature dependence of Sm valence in SmB6 studied by X-ray absorption spectroscopy. J. Phys. Conf. Ser. 176, 012034 (2009).

    Article  Google Scholar 

  22. Butch, N. P. et al. Pressure-resistant intermediate valence in the Kondo insulator SmB6 . Phys. Rev. Lett. 116, 156401 (2016).

    Article  Google Scholar 

  23. Varma, C. M. Mixed-valence compounds. Rev. Mod. Phys. 48, 219–238 (1976).

    Article  CAS  Google Scholar 

  24. Lawrence, J. M., Riseborough, P. S. & Parks, R. D. Valence fluctuation phenomena. Rep. Prog. Phys. 44, 1–84 (1981).

    Article  Google Scholar 

Download references

Acknowledgements

This work was supported by NSF grant DMR-1350122. V.M.G. acknowledges the support from DOEBES (DESC0001911) and Simons Foundation. M.D. acknowledges the support from NSF (DMR-1506547). We thank S. Thomas, B. Casas and D. Trinh for technical assistance.

Author information

Authors and Affiliations

  1. Department of Physics and Astronomy, University of California, Irvine, California 92697, USA

    A. Stern, Z. Fisk & J. Xia

  2. Department of Physics, Kent State University, Kent, Ohio 44242, USA

    M. Dzero

  3. Department of Physics, Joint Quantum Institute, University of Maryland, College Park, Maryland 20742, USA

    V. M. Galitski

Authors
  1. A. Stern
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. M. Dzero
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. V. M. Galitski
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Z. Fisk
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. J. Xia
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

A.S. performed the measurements. M.D. and V.M.G. developed the theory. Z.F. fabricated the samples. J.X. designed the project. All authors discussed the result, and contributed to the writing of the manuscript.

Corresponding author

Correspondence to J. Xia.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

Supplementary Information (PDF 569 kb)

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Stern, A., Dzero, M., Galitski, V. et al. Surface-dominated conduction up to 240 K in the Kondo insulator SmB6 under strain. Nature Mater 16, 708–711 (2017). https://doi.org/10.1038/nmat4888

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nmat4888

This article is cited by

Search

Advanced 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