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Multiple-step melting in two-dimensional hexatic liquid-crystal films
1C.-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, Buf.
Science (New York, N.Y.)
|June 5, 1998
Summary
Two-dimensional melting reveals a new intermediate liquid phase in free-standing liquid-crystal films. This discovery challenges existing theories of two-dimensional melting and suggests a revised understanding of phase transitions.
Area of Science:
- Condensed matter physics
- Materials science
- Physical chemistry
Background:
- Two-dimensional (2D) melting theories predict specific phase transitions.
- Previous heat-capacity measurements showed anomalies contradicting these theories.
Purpose of the Study:
- To investigate the melting transitions in 2D free-standing liquid-crystal films.
- To reconcile experimental observations with theoretical predictions of 2D melting.
Main Methods:
- In situ electron-diffraction measurements.
- Optical-reflectivity measurements.
- Analysis of heat-capacity data.
Main Results:
- Observed an unexpected three-stage melting transition in 2D liquid-crystal films.
- Identified two phases between solid and liquid: a hexatic phase and an intermediate liquid phase.
- The intermediate liquid phase exhibits short-range positional correlations but lacks long-range orientational order.
Conclusions:
- The existence of an intermediate isotropic phase may alter the understanding of 2D melting.
- This finding could reconcile discrepancies between current experiments and 2D melting theories.