Spin-ordering and magnon collective modes for two-dimensional electron lattices in strong magnetic fields

TL;DR

This paper investigates the spin ordering and collective magnon excitations in a two-dimensional electron Wigner crystal under strong magnetic fields, revealing a ferromagnetic ground state with low spin-stiffness compared to fluid states.

Contribution

It introduces a detailed analysis of spin order and magnon modes in 2D Wigner crystals using Hartree-Fock methods, highlighting ferromagnetism at zero temperature.

Findings

Ground state is ferromagnetic at T=0.

Magnon spin-stiffness is significantly lower than in fluid states.

Magnetic properties depend on Landau level filling factors.

Abstract

We study the spin-ordering and the magnon collective modes of the two-dimensional Wigner crystal state at strong magnetic fields. Our work is based on the Hartree-Fock approximation for the ground state and the time-dependent Hartree-Fock approximation for the collective modes. We find that the ground state is ferromagnetic, i.e that all spins are aligned at T=0 even when the electronic g-factor is negligibly small. The magnon calculations show that the spin-stiffness is much smaller in the crystal state than in fluid states which occur at nearby Landau level filling factors.