Wigner crystal of a two-dimensional electron gas with a strong spin-orbit interaction

TL;DR

This paper investigates how strong Rashba spin-orbit coupling influences the formation and symmetry properties of a Wigner crystal in a two-dimensional electron gas, revealing spontaneous symmetry breaking and lattice deformation.

Contribution

It demonstrates that strong spin-orbit interaction can induce a new Wigner crystal phase with broken rotational symmetry and a doubled unit cell, a novel effect not previously described.

Findings

Degeneracy of the lower subband leads to symmetry breaking.

The triangular lattice becomes slightly squeezed.

The unit cell contains two electrons due to symmetry breaking.

Abstract

The Wigner-crystal phase of two-dimensional electrons interacting via the Coulomb repulsion and subject to a strong Rashba spin-orbit coupling is investigated. For low enough electronic densities the spin-orbit band splitting can be larger than the zero-point energy of the lattice vibrations. Then the degeneracy of the lower subband results in a spontaneous symmetry breaking of the vibrational ground state. The $60^{\circ}-$rotational symmetry of the triangular (spin-orbit coupling free) structure is lost, and the unit cell of the new lattice contains two electrons. Breaking the rotational symmetry also leads to a (slight) squeezing of the underlying triangular lattice.