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Abstract:
Using videomicroscopy data of a two-dimensional colloidal system the bond-order correlation function G6 is calculated and used to determine both the orientational correlation length ξ6 in the liquid phase and the modulus of orientational stiffness, Frank’s constant FA, in the hexatic phase. The latter is an anisotropic fluid phase between the crystalline and the isotropic liquid phase. FA is found to be finite within the hexatic phase, takes the value 72∕π at the hexatic↔isotropic
liquid phase transition, and diverges at the
hexatic↔crystal transition as predicted by the Kosterlitz-Thouless-Halperin-Nelson-Young theory. This is a quantitative test of the mechanism of breaking the orientational symmetry by disclination unbinding.
