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.

Liquid-hexatic phase transitions in single molecular layers of liquid-crystal films


THEORIES of melting in two dimensions1–3 predict that it may have a very different character from the three-dimensional transition. In particular, Halperin and Nelson2 proposed that an intermediate hexatic phase, with long-range orientational but not positional order, might intervene between the two-dimensional solid and liquid. Hexatic order has since been identified in three-dimensional liquid-crystal phases4. Several liquid-crystal compounds that exhibit a hexatic mesophase can form free-standing films ranging from two to thousands of molecular layers in thick-ness, permitting experimental investigation of theories of melting in two dimensions, free from the effects of a substrate. We have previously studied transitions between liquid, hexatic and crystal-line phases in films of n-heptyl-4'-n-pentyloxybiphenyl-4-carboxylate (75OBC), and for films thicker than four layers we observed separate liquid-hexatic transitions for surface and inner layers5, revealed by heat-capacity measurements. Here we report that improvements to our measurement technique allow us to identify these transitions in individual molecular layers, even in films just three layers thick. We also observe a single liquid-hexatic transition in a two-layer film. These films therefore provide model systems for the study of truly two-dimensional phase transitions.

This is a preview of subscription content

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.


  1. 1

    Kosterlitz, J. M. & Thouless, D. J. J. Phys. C6, 1181 (1973).

    ADS  CAS  Google Scholar 

  2. 2

    Halperin, B. I. & Nelson, D. R. Phys. Rev. Lett. 41, 121 (1978).

    ADS  MathSciNet  CAS  Article  Google Scholar 

  3. 3

    Young, A. P. Phys. Rev. B19, 1855 (1977).

    Article  Google Scholar 

  4. 4

    Pindak, R., Moncton, D. E., Davey, S. D. & Goodby, J. W. Phys. Rev. Lett. 46, 1135 (1981).

    ADS  CAS  Article  Google Scholar 

  5. 5

    Geer, R. et al. Phys. Rev. Lett 66, 1322 (1991).

    ADS  CAS  Article  Google Scholar 

  6. 6

    Geer, R. Stoebe, T., Pitchford, T. & Huang, C. C. Rev. scient. Instrum. 62, 415 (1991).

    ADS  CAS  Article  Google Scholar 

  7. 7

    Young, C. Y., Pindak, R., Clark, N. A. & Meyer, R. B. Phys. Rev. Lett. 40, 773 (1978).

    ADS  CAS  Article  Google Scholar 

  8. 8

    Levelut, A. M. J. Phys. Colloq. 37, C3–51 (1976).

    Article  Google Scholar 

  9. 9

    Pindak, R., Bishop, D. J. & Sprenger, W. O. Phys. Rev. Lett. 44, 1461 (1980).

    ADS  CAS  Article  Google Scholar 

  10. 10

    Heinekamp, S. et al. Phys. Rev. Lett 52, 1017 (1984).

    ADS  CAS  Article  Google Scholar 

  11. 11

    Sirota, E. B., Pershan, P. S., Amador, S. & Sorensen, L. B. Phys. Rev. A35, 2283 (1987).

    ADS  CAS  Article  Google Scholar 

  12. 12

    Berker, A. N. & Nelson, D. R. Phys, Rev. B19, 2488 (1979).

  13. 13

    Cheng, M., Ho, J. T., Hui, S. W. & Pindak, R. Phys. Rev. Lett 61, 550 (1988).

    ADS  CAS  Article  Google Scholar 

  14. 14

    Solla, S. & Riedel, E. K. Phys. Rev. B23, 6008 (1981).

    ADS  CAS  Article  Google Scholar 

Download references

Author information



Rights and permissions

Reprints and Permissions

About this article

Cite this article

Geer, R., Stoebe, T., Huang, C. et al. Liquid-hexatic phase transitions in single molecular layers of liquid-crystal films. Nature 355, 152–154 (1992).

Download citation

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