Skip to main content

Thank you for visiting 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.

Polarons and confinement of electronic motion to two dimensions in a layered manganite


A remarkable feature of layered transition-metal oxides—most famously, the high-temperature superconductors—is that they can display hugely anisotropic electrical and optical properties (for example, seeming to be insulating perpendicular to the layers and metallic within them), even when prepared as bulk three-dimensional single crystals. This is the phenomenon of ‘confinement’, a concept at odds with the conventional theory of solids, and recognized1 as due to magnetic and electron–lattice interactions within the layers that must be overcome at a substantial energy cost if electrons are to be transferred between layers. The associated energy gap, or ‘pseudogap’, is particularly obvious in experiments where charge is moved perpendicular to the planes, most notably scanning tunnelling microscopy2 and polarized infrared spectroscopy3. Here, using the same experimental tools, we show that there is a second family of transition-metal oxides—the layered manganites La2-2xSr1+2xMn2O7—with even more extreme confinement and pseudogap effects. The data demonstrate quantitatively that because the charge carriers are attached to polarons (lattice- and spin-textures within the planes), it is as difficult to remove them from the planes through vacuum-tunnelling into a conventional metallic tip, as it is for them to move between Mn-rich layers within the material itself.

Your institute does not have access to this article

Relevant articles

Open Access articles citing this article.

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Structure and bulk transport properties of La1.4Sr1.6Mn2O7.
Figure 2: Unprocessed STM micrographs of La1.4Sr1.6Mn2O7.
Figure 3: Temperature-dependent STM spectroscopy of La1.4Sr1.6Mn2O7.
Figure 4: Optical conductivity deduced from near-normal-incidence reflectivity measured on single crystal samples (sharp peaks at 20–80 meV are due to phonons)19.


  1. Anderson, P. W. The resonating valence bond state in La2CuO4 and superconductivity. Science 235, 1196–1198 (1987)

    ADS  CAS  Article  Google Scholar 

  2. Renner, Ch., Revaz, B., Genoud, J. Y., Kadowaki, K. & Fischer, Ø. Pseudogap precursor of the superconducting gap in under- and overdoped Bi2Sr2CaCu2O8+δ . Phys. Rev. Lett. 80, 149–152 (1998)

    ADS  CAS  Article  Google Scholar 

  3. Uchida, S., Tamasaku, K. & Tajima, S. c-axis optical spectra and charge dynamics in La2-xSrxCuO4 . Phys. Rev. B 53, 14558–14574 (1996)

    ADS  CAS  Article  Google Scholar 

  4. von Helmolt, R., Wecker, J., Holzapfel, B., Schultz, L. & Samwer, K. Giant negative magnetoresistance in perovskitelike La2/3Ba1/3MnOx ferromagnetic films. Phys. Rev. Lett. 71, 2331–2333 (1993)

    ADS  CAS  Article  Google Scholar 

  5. Jin, S. et al. Thousandfold change in resistivity in magnetoresistive La-Ca-Mn-O films. Science 264, 413–415 (1994)

    ADS  CAS  Article  Google Scholar 

  6. Millis, A. J. Lattice effects in magnetoresistive manganese perovskites. Nature 392, 147–150 (1998)

    ADS  CAS  Article  Google Scholar 

  7. Ramirez, A. P. et al. Thermodynamic and electron diffraction signatures of charge and spin ordering in La1-xCaxMnO3 . Phys. Rev. Lett. 76, 3188–3191 (1996)

    ADS  CAS  Article  Google Scholar 

  8. Mori, S., Chen, C. H. & Cheong, S.-W. Pairing of charge-ordered stripes in (La,Ca)MnO3 . Nature 392, 473–476 (1998)

    ADS  CAS  Article  Google Scholar 

  9. Tokura, Y. & Nagaosa, N. Orbital physics in transition-metal oxides. Science 288, 462–468 (2000)

    ADS  CAS  Article  Google Scholar 

  10. Perring, T. G., Aeppli, G., Kimura, T., Tokura, Y. & Adams, M. A. Ordered stack of spin valves in a layered magnetoresistive perovskite. Phys. Rev. B 58, R14693–R14696 (1998)

    ADS  CAS  Article  Google Scholar 

  11. Dagotto, E. in Nanoscale Phase Separation and Colossal Magnetoresistance (eds Cardona, M. et al.) (Springer Series in Solid State Sciences Vol. 136, Springer, New York, 2003)

    Book  Google Scholar 

  12. Kimura, T. & Tokura, Y. Layered magnetic manganites. Annu. Rev. Mater. Sci. 30, 451–474 (2000)

    ADS  CAS  Article  Google Scholar 

  13. Abrikosov, A. A. Quantum interference effects in quasi-two-dimensional metals. Phys. Rev. B 61, 7770–7774 (2000)

    ADS  CAS  Article  Google Scholar 

  14. Moritomo, Y., Asamitsu, A., Kuwahara, H. & Tokura, Y. Giant magnetoresistance of manganese oxides with a layered perovskite structure. Nature 380, 141–144 (1996)

    ADS  CAS  Article  Google Scholar 

  15. Becker, T. et al. Intrinsic inhomogeneities in manganite thin films investigated with scanning tunneling spectroscopy. Phys. Rev. Lett. 89, 237203 (2002)

    ADS  CAS  Article  Google Scholar 

  16. Fäth, M. et al. Spatially inhomogeneous metal-insulator transition in doped manganites. Science 285, 1540–1542 (1999)

    Article  Google Scholar 

  17. Kimura, T. et al. Interplane tunneling magnetoresistance in a layered manganite crystal. Science 274, 1698–1701 (1996)

    ADS  CAS  Article  Google Scholar 

  18. Kittel, C. Introduction to Solid State Physics (Wiley and Sons, Inc., New York, 1976)

    MATH  Google Scholar 

  19. Ishikawa, T., Tobe, K., Kimura, T., Katsufuji, T. & Tokura, Y. Optical study on the doping and temperature dependence of the anisotropic electronic structure in bilayered manganites: La2-2xSr1+2xMn2O7 (0.3 ≤ x ≤ 0.5). Phys. Rev. B 62, 12354–12362 (2000)

    ADS  CAS  Article  Google Scholar 

  20. Freeland, J. W. et al. Full bulk spin polarization and intrinsic tunnel barriers at the surface of layered manganites. Nature Mater. 4, 62–67 (2005)

    ADS  CAS  Article  Google Scholar 

  21. Konoto, M. et al. Direct imaging of temperature-dependent layered antiferromagnetism of a magnetic oxide. Phys. Rev. Lett. 93, 107201 (2004)

    ADS  CAS  Article  Google Scholar 

  22. Blanco, J. M. et al. First-principles simulations of STM images: From tunneling to the contact regime. Phys. Rev. B 70, 085405 (2004)

    ADS  MathSciNet  Article  Google Scholar 

  23. Perring, T. G., Aeppli, G., Moritomo, Y. & Tokura, Y. Antiferromagnetic short-range order in a two dimensional manganite exhibiting giant magnetoresistance. Phys. Rev. Lett. 78, 3197–3200 (1997)

    ADS  CAS  Article  Google Scholar 

  24. Campbell, B. J. et al. Structure of nanoscale polaron correlations in La1.2Sr1.8Mn2O7 . Phys. Rev. B 65, 014427 (2001)

    ADS  Article  Google Scholar 

  25. Dessau, D. S. et al. k-dependent electronic structure, a large “ghost” Fermi surface, and a pseudogap in a layered magnetoresistive oxide. Phys. Rev. Lett. 81, 192–195 (1998)

    ADS  CAS  Article  Google Scholar 

  26. Wei, J. Y. T., Yeh, N. C. & Vasquez, R. P. Tunneling evidence of half-metallic ferromagnetism in La0.7Ca0.3MnO3 . Phys. Rev. Lett. 79, 5150–5153 (1997)

    ADS  CAS  Article  Google Scholar 

  27. Mannella, N. et al. Nodal quasiparticle in pseudogapped colossal magnetoresistive manganites. Nature 438, 474–478 (2005)

    ADS  CAS  Article  Google Scholar 

  28. Renner, Ch., Aeppli, G., Kim, B. G., Soh, Y. A. & Cheong, S.-W. Atomic-scale images of charge ordering in a mixed-valence manganite. Nature 416, 518–521 (2002)

    ADS  CAS  Article  Google Scholar 

  29. Crommie, M. F., Lutz, C. P. & Eigler, D. M. Imaging standing waves in a two-dimensional electron gas. Nature 363, 524–527 (1993)

    ADS  CAS  Article  Google Scholar 

  30. Hoffman, J. E. et al. Imaging quasiparticle interference in Bi2Sr2CaCu2O8+δ . Science 297, 1148–1151 (2002)

    ADS  CAS  Article  Google Scholar 

  31. Yazdani, A., Howald, C. M., Lutz, C. P., Kapitulnik, A. & Eigler, D. M. Impurity-induced bound excitations on the surface of Bi2Sr2CaCu2O8 . Phys. Rev. Lett. 83, 176–179 (1999)

    ADS  CAS  Article  Google Scholar 

Download references


We thank T. Ishikawa for providing the optical conductivity data shown in Fig. 4, D. McPhail and R. Chater for the static SIMS measurements, and A. Fisher and J. Mesot for discussions. We acknowledge support from a Wolfson–Royal Society Research Merit Award, the NEC corporation, and the European Commission through a FW6 STREP programme. H.M.R. thanks T. F. Rosenbaum for support through an NSF Materials Research Science and Engineering Centers grant.

Author information

Authors and Affiliations


Corresponding author

Correspondence to Ch. Renner.

Ethics declarations

Competing interests

Reprints and permissions information is available at The authors declare no competing financial interests.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Rønnow, H., Renner, C., Aeppli, G. et al. Polarons and confinement of electronic motion to two dimensions in a layered manganite. Nature 440, 1025–1028 (2006).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


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