Anisotropic defect-mediated melting of two-dimensional colloidal crystals

Phys Rev Lett. 2004 Sep 3;93(10):105702. doi: 10.1103/PhysRevLett.93.105702. Epub 2004 Sep 3.

Abstract

The melting transition of anisotropic two-dimensional (2D) crystals is studied in a model system of superparamagnetic colloids. The anisotropy of the induced dipole-dipole interaction is varied by tilting the external magnetic field off the normal to the particle plane. By analyzing the time-dependent Lindemann parameter as well as translational and orientational order we observe a 2D smecticlike phase. The Kosterlitz-Thouless-Halperin-Nelson-Young scenario of isotropic melting is modified: dislocation pairs and dislocations appear with different probabilities depending on their orientation with respect to the in-plane field.