The Berezinskii–Kosterlitz–Thouless Transition and Melting Scenarios of Two-Dimensional Systems

The paper discusses current theories of melting of two-dimensional systems that are mainly based on the concepts of the Berezinskii–Kosterlitz–Thouless (BKT) theory of phase transitions in two-dimensional systems with continuous symmetry. At present there are three basic scenarios of melting of two-dimensional crystals that as shown by computer simulation are implemented in the two-dimensional system of Hertzian spheres used to describe the behavior of a number of soft matter systems. The system demonstrates complex phase behavior with the presence of all three melting scenarios in the various parts of the phase diagram.