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.

Tailoring the nature and strength of electron–phonon interactions in the SrTiO3(001) 2D electron liquid

Abstract

Surfaces and interfaces offer new possibilities for tailoring the many-body interactions that dominate the electrical and thermal properties of transition metal oxides1,2,3,4. Here, we use the prototypical two-dimensional electron liquid (2DEL) at the SrTiO3(001) surface5,6,7 to reveal a remarkably complex evolution of electron–phonon coupling with the tunable carrier density of this system. At low density, where superconductivity is found in the analogous 2DEL at the LaAlO3/SrTiO3 interface8,9,10,11,12,13, our angle-resolved photoemission data show replica bands separated by 100 meV from the main bands. This is a hallmark of a coherent polaronic liquid and implies long-range coupling to a single longitudinal optical phonon branch. In the overdoped regime the preferential coupling to this branch decreases and the 2DEL undergoes a crossover to a more conventional metallic state with weaker short-range electron–phonon interaction. These results place constraints on the theoretical description of superconductivity and allow a unified understanding of the transport properties in SrTiO3-based 2DELs.

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

Relevant articles

Open Access articles citing this article.

Access options

Buy article

Get time limited or full article access on ReadCube.

$32.00

All prices are NET prices.

Figure 1: A two-dimensional liquid of large polarons in SrTiO3.
Figure 2: Evolution of the 2DEL spectral function with carrier concentration.
Figure 3: Effective mass and quasiparticle residue in the SrTiO3 2DEL.

References

  1. Mannhart, J. & Schlom, D. G. Oxide interfaces—an opportunity for electronics. Science 327, 1607–1611 (2010).

    CAS  Article  Google Scholar 

  2. Lee, J. J. et al. Interfacial mode coupling as the origin of the enhancement of Tc in FeSe films on SrTiO3 . Nature 515, 245–248 (2014).

    CAS  Article  Google Scholar 

  3. Zubko, P., Gariglio, S., Gabay, M., Ghosez, P. & Triscone, J.-M. Interface physics in complex oxide heterostructures. Annu. Rev. Condens. Matter Phys. 2, 141–165 (2011).

    CAS  Article  Google Scholar 

  4. Ohtomo, A. & Hwang, H. Y. A high-mobility electron gas at the LaAlO3/SrTiO3 heterointerface. Nature 427, 423–426 (2004).

    CAS  Article  Google Scholar 

  5. Meevasana, W. et al. Creation and control of a two-dimensional electron liquid at the bare SrTiO3 surface. Nature Mater. 10, 114–118 (2011).

    CAS  Article  Google Scholar 

  6. Santander-Syro, A. F. et al. Two-dimensional electron gas with universal subbands at the surface of SrTiO3 . Nature 469, 189–193 (2011).

    CAS  Article  Google Scholar 

  7. King, P. D. C. et al. Quasiparticle dynamics and spin-orbital texture of the SrTiO3 two-dimensional electron gas. Nature Commun. 5, 3414 (2014).

    CAS  Article  Google Scholar 

  8. Thiel, S., Hammerl, G., Schmehl, A., Schneider, C. W. & Mannhart, J. Tunable quasi-two-dimensional electron gases in oxide heterostructures. Science 313, 1942–1945 (2006).

    CAS  Article  Google Scholar 

  9. Reyren, N. et al. Superconducting interfaces between insulating oxides. Science 317, 1196–1199 (2007).

    CAS  Article  Google Scholar 

  10. Caviglia, A. D. et al. Electric field control of the LaAlO3/SrTiO3 interface ground state. Nature 456, 624–627 (2008).

    CAS  Article  Google Scholar 

  11. Richter, C. et al. Interface superconductor with gap behaviour like a high-temperature superconductor. Nature 502, 528–531 (2008).

    Article  Google Scholar 

  12. Cheng, G. et al. Electron pairing without superconductivity. Nature 521, 196–199 (2015).

    CAS  Article  Google Scholar 

  13. Boschker, H., Richter, C., Fillis-Tsirakis, E., Schneider, C. W. & Mannhart, J. Electron–phonon coupling and the superconducting phase diagram of the LaAlO3-SrTiO3 interface. Sci. Rep. 5, 12309 (2015).

    CAS  Article  Google Scholar 

  14. Plumb, N. C. et al. Mixed dimensionality of confined conducting electrons in the surface region of SrTiO3 . Phys. Rev. Lett. 113, 086801 (2014).

    CAS  Article  Google Scholar 

  15. Wang, Z. et al. Anisotropic two-dimensional electron gas at SrTiO3(110). Proc. Natl Acad. Sci. USA 111, 3933–3937 (2014).

    CAS  Article  Google Scholar 

  16. McKeown Walker, S. et al. Carrier-density control of the SrTiO3 (001) surface 2D electron gas studied by ARPES. Adv. Mater. 27, 3894–3899 (2015).

    Article  Google Scholar 

  17. Gervais, F., Servoin, J.-L., Baratoff, A., Bednorz, J. G. & Binnig, G. Temperature dependence of plasmons in Nb-doped SrTiO3 . Phys. Rev. B 47, 8187–8194 (1993).

    CAS  Article  Google Scholar 

  18. Chang, Y. J., Bostwick, A., Kim, Y. S., Horn, K. & Rotenberg, E. Structure and correlation effects in semiconducting SrTiO3 . Phys. Rev. B 81, 235109 (2010).

    Article  Google Scholar 

  19. Devreese, J. T. & Alexandrov, A. S. Fröhlich polaron and bipolaron: recent developments. Rep. Prog. Phys. 72, 066501 (2009).

    Article  Google Scholar 

  20. Alexandrov, A. S. Theory of Superconductivity: From Weak to Strong Coupling (Series in Condensed Matter Physics, Institute of Physics, 2003).

    Book  Google Scholar 

  21. Moser, S. et al. Tunable polaronic conduction in anatase TiO2 . Phys. Rev. Lett. 110, 196403 (2013).

    CAS  Article  Google Scholar 

  22. Chen, C., Avila, J., Frantzeskakis, E., Levy, A. & Asensio, M. C. Observation of a two-dimensional liquid of Fröhlich polarons at the bare SrTiO3 surface. Nature Commun. 6, 8585 (2015).

    CAS  Article  Google Scholar 

  23. Salluzzo, M. et al. Orbital reconstruction and the two-dimensional electron gas at the LaAlO3/SrTiO3 interface. Phys. Rev. Lett. 102, 166804 (2009).

    CAS  Article  Google Scholar 

  24. Lee, T. D., Low, F. E. & Pines, D. The motion of slow electrons in a polar crystal. Phys. Rev. 90, 297–302 (1953).

    Article  Google Scholar 

  25. Mishchenko, A. S., Prokof’ev, N. V., Sakamoto, A. & Svistunov, B. V. Diagrammatic quantum Monte Carlo study of the Fröhlich polaron. Phys. Rev. B 62, 6317–6336 (2000).

    CAS  Article  Google Scholar 

  26. van Mechelen, J. L. M. et al. Electron–phonon interaction and charge carrier mass enhancement in SrTiO3 . Phys. Rev. Lett. 100, 226403 (2008).

    CAS  Article  Google Scholar 

  27. Devreese, J. T., Klimin, S. N., van Mechelen, J. L. M. & van der Marel, D. Many-body large polaron optical conductivity in SrTi1−xNbxO3 . Phys. Rev. B 81, 125119 (2010).

    Article  Google Scholar 

  28. Mishchenko, A. S., Nagaosa, N. & Prokof’ev, N. Diagrammatic Monte Carlo method for many-polaron problems. Phys. Rev. Lett. 113, 166402 (2014).

    Article  Google Scholar 

  29. Cancellieri, C. et al. Polaronic metal state at the LaAlO3/SrTiO3 interface. Nature Commun. 7, 10386 (2016).

    CAS  Article  Google Scholar 

  30. Mikheev, E. et al. Limitations to the room temperature mobility of two- and three-dimensional electron liquids in SrTiO3 . Appl. Phys. Lett. 106, 062102 (2015).

    Article  Google Scholar 

  31. Lin, X. et al. Critical doping for the onset of a two-band superconducting ground state in SrTiO3−δ . Phys. Rev. Lett. 112, 207002 (2014).

    Article  Google Scholar 

  32. Klimin, S. N., Tempere, J., Devreese, J. T. & van der Marel, D. Interface superconductivity in LaAlO3/SrTiO3 . Phys. Rev. B 89, 184514 (2014).

    Article  Google Scholar 

  33. Gorkov, L. P. Phonon mechanism in the most dilute superconductor: n-type SrTiO3. Preprint at http://arxiv.org/abs/1508.00529 (2015).

  34. Emin, D. Formation, motion, and high-temperature superconductivity of large bipolarons. Phys. Rev. Lett. 62, 1544–1547 (1989).

    CAS  Article  Google Scholar 

  35. Hohenadler, M., Aichhorn, M. & Von Der Linden, W. Single-particle spectral function of the Holstein–Hubbard bipolaron. Phys. Rev. B 71, 014302 (2004).

    Article  Google Scholar 

  36. Wang, Q.-Y. et al. Interface-induced high-temperature superconductivity in single unit-cell FeSe films on SrTiO3 . Chin. Phys. Lett. 29, 037402 (2012).

    Article  Google Scholar 

Download references

Acknowledgements

We thank A. Fête, M. Grilli, L. Patthey, V. Strocov, J.-M. Triscone, D. van der Marel and Z. Zhong for discussions. The ARPES work was supported by the Swiss National Science Foundation (200021-146995). The spectral function calculations were supported at SLAC and Stanford University by the US Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, under Contract No. DE-AC02-76SF00515, and by the Computational Materials and Chemical Sciences Network (CMCSN), under Contract No. DE-SC0007091. A portion of the computational work was performed using the resources of the National Energy Research Scientific Computing Center supported by the US Department of Energy, Office of Science, under Contract No. DE-AC02-05CH11231. M.S. acknowledges financial support by the Sino-Swiss Science and Technology Cooperation (No. IZLCZ2138954), J.S.-B. by the Impuls- und Vernetzungsfonds der Helmholtz Gemeinschaft (Grant No. HRJRG-408), P.D.C.K. by the UK-EPSRC (EP/I031014/1) and the Royal Society, U.D. by the ERC Advanced Grant ‘OxideSurfaces’ and W.M. by the Thailand Research Fund (TRF) under the TRF Senior Research Scholar, Grant No. RTA5680008. We acknowledge Diamond Light Source for time on beamline I05 under proposal SI11741.

Author information

Authors and Affiliations

Authors

Contributions

ARPES measurements were carried out by Z.W., S.M.W., Z.R., F.Y.B., A.d.l.T., S.R., M.R. and F.B. and analysed by Z.W., A.T. and F.B.; N.C.P., M.S., P.H., J.S.-B., A.V., T.K.K. and M.H. were responsible for the synchrotron beam lines used in the experiments; Y.W., B.M. and T.P.D. performed the exact diagonalization calculations. F.B. wrote the manuscript with contributions by Z.W., Y.W. and A.T.; T.P.D., M.R. and F.B. were responsible for project planning, direction and resources. All authors contributed to the scientific discussion of the results.

Corresponding authors

Correspondence to Z. Wang or F. Baumberger.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

Supplementary Information (PDF 2203 kb)

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Wang, Z., McKeown Walker, S., Tamai, A. et al. Tailoring the nature and strength of electron–phonon interactions in the SrTiO3(001) 2D electron liquid. Nature Mater 15, 835–839 (2016). https://doi.org/10.1038/nmat4623

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nmat4623

This article is cited by

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