Melting of Coulomb-interacting classical particles in 2D irregular traps

The “melting” of self-formed rigid structures made of a small number of interacting classical particles confined in an irregular two-dimensional space is investigated using Monte Carlo simulations. It is shown that the interplay of long-range Coulomb repulsions between these particles and the irregular confinement yields a solid-like phase at low temperatures that possesses a bond-orientational order, however, the positional order is depleted even at the lowest temperatures. Upon including thermal fluctuations, this solid-like phase smoothly crosses over to a liquid-like phase by destroying the bond-orientational order. The collapse of solidity is shown to be defect mediated, and aided by the proliferation of free disclinations. The behaviour of different physical observables across the crossover region is studied. These results will help us quantifying the melting found in experiments on systems with confined geometries. Copyright EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg 2013