Fizika Nizkikh Temperatur: Volume 46, Number 10 (October 2020), p. 1161-1170 ( to contents , go back )
Melting of different shape 2D electron clusters
V. E. Syvokon
B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine Kharkiv 61103, Ukraine
Received May 12, 2020, published online August 21, 2020
Melting of two-dimensional clusters is studied by molecular dynamics method. The clusters can be created in the electron systems over superfluid helium with holding electrodes of triangular, square, hexagonal, and round shape. The surface electron density ns = 108 cm–2 is fixed. The clusters studied contain from 3 to 406 electrons. The transition to a non-ordered state for the defectfree clusters is shown to occur sharply and the melting temperature Тmelt can be found easily. The Тmelt dependence on cluster size is observed for the clusters containing less than 400 particles (N < 400). The ordering in square clusters with N < 50 is imposed by boundary conditions but at N > 100 one can see the triangular lattice with defects near the edge of the cluster. In the round clusters electrons can move easily in the angular direction even at enough low temperatures, but the temperature of the “radial” melting agrees with the melting temperature of the small square clusters. The transition to a non-ordered state for clusters with defects starts near the defect and spread gradually over the whole cluster. In this case, there is no clear definition of the melting point.
Key words: cluster, Wigner crystal, melting, molecular dynamics.