2-DIMENSIONAL MICROCLUSTERS OF VORTICES - SHELL STRUCTURE AND MELTING

The melting of two-dimensional microclusters of ''particles'' which re pel one another according to a logarithmic law and are confined by an external quadratic potential is investigated. The model describes Abri kosov vortices in a superconducting island of vortices in a rotating s uperfluid liquid and electrons in a semiconductor nanostructure surrou nded by a low-permittivity medium. The structure of clusters and its d ependence on temperature and melting are investigated. The melting of microclusters of vortices proceeds in two stages: 1. A transition from a frozen phase into a state corresponding to rotational reorientation of crystal shells relative to one another. 2. At a higher temperature , the radial order vanishes. This is connected with the fact that the barrier for rotation of the shells is much lower than the barrier for radial breakup of the shells. (C) 1997 American Institute of Physics.