Crystallization of a classical two-dimensional electron system: Positional and orientational orders

TL;DR

This study uses molecular dynamics to analyze crystallization in a 2D classical electron system, revealing quasi-long-range positional order and long-range orientational order, and discussing the hexatic phase.

Contribution

First calculation of positional and orientational correlation functions in a 2D Coulomb system, showing quasi-long-range positional order and long-range orientational order.

Findings

Solid phase exhibits power-law positional order.

Long-range orientational order is present.

Discussion of the hexatic phase between liquid and solid.

Abstract

Crystallization of a classical two-dimensional one-component plasma (electrons interacting with the Coulomb repulsion in a uniform neutralizing positive background) is investigated with a molecular dynamics simulation. The positional and the orientational correlation functions are calculated for the first time. We have found an indication that the solid phase has a quasi-long-range (power-law) positional order along with a long-range orientational order. This indicates that, although the long-range Coulomb interaction is outside the scope of Mermin's theorem, the absence of ordinary crystalline order at finite temperatures applies to the electron system as well. The `hexatic' phase, which is predicted between the liquid and the solid phases by the Kosterlitz-Thouless-Halperin-Nelson-Young theory, is also discussed.