Multiple-Step Melting in Two-Dimensional Hexatic Liquid-Crystal Films
Chia-Fu Chou,
*
Anjun J. Jin,
S. W. Hui,
C. C. Huang,
John T. Ho
An unexpected three-stage melting transition has been observed in
two-dimensional (2D) free-standing liquid-crystal films by in situ
electron-diffraction and optical-reflectivity measurements. These data
suggest the existence of two phases between the 2D solid and liquid: a
hexatic phase and, at a higher temperature, an intermediate liquid
phase with hexatic-like positional correlations (~40 angstroms) but
no long-range orientational order. Previous high-resolution
heat-capacity measurements have revealed a divergent-like anomaly at
the hexatic-liquid transition that sharply contradicts the predictions
of 2D melting theories. The observation of an intermediate isotropic
phase may alter our understanding of 2D melting and lead to
reconciliation between current experiments and theories.
C.-F. Chou, Department of Physics, Princeton University,
Princeton, NJ 08544, USA.
A. J. Jin, Applied Materials, 3320 Scott Boulevard, Mailstop 1114, Santa Clara, CA 95054, USA.
S. W. Hui, Department of Biophysics, Roswell Park
Cancer Institute, Buffalo, NY 14263, USA.
C. C. Huang, School of Physics and Astronomy,
University of Minnesota, Minneapolis, MN 55455, USA.
J. T. Ho, Department of Physics, State University of New York at
Buffalo, Buffalo, NY 14260, USA.
*
To whom correspondence should be addressed. E-mail:
cchou{at}princeton.edu
