Structural Transition of Wigner Crystal on Liquid Substrate

TL;DR

This paper investigates the phase transition of a Wigner crystal on a liquid substrate, revealing a transition from triangular to square lattice structures driven by surface interactions at low electron densities.

Contribution

It introduces a novel analysis of the electron lattice structure transition influenced by surface-induced forces, expanding understanding of electron solids on liquid surfaces.

Findings

Identification of a parameter regime favoring square lattice over triangular lattice.

Mapping of the first-order transition curve between lattice geometries.

Insight into charge-density wave instability related to multi-electron dimples.

Abstract

The physics of an electron solid, held on a cryogenic liquid surface by a pressing electric field, is examined in a low-density regime that has not been explored before. We consider the effect of the pressing field in distorting the surface at the position of each electron and hence inducing an attractive force between the electrons. The system behavior is described in terms of an interplay between the repulsive Coulomb interaction and the attractive surface-induced interaction between individual electrons. For small densities and large enough pressing fields, we find a parameter regime where a square lattice is more favorable than the usual triangular lattice; we map out the first-order transition curve separating the two lattice geometries at zero temperature. In addition, our description allows an alternate static perspective on the charge-density wave instability of the system, corresponding to the formation of multi-electron dimples.