Interacting spin-droplets and magnetic properties of a low-density two-dimensional electron gas

TL;DR

This paper proposes that magnetic susceptibility in low-density 2D electron gases arises from localized spin-droplets, which interact ferromagnetically, forming a 2D Heisenberg ferromagnet with S=1, offering a new understanding of magnetic properties in such systems.

Contribution

It introduces a model where spin-droplets explain magnetic susceptibility, and identifies their ferromagnetic interactions and spin state, providing a new perspective on 2D electron gas magnetism.

Findings

Magnetic susceptibility data suggest localized spin-droplets.

Droplets interact ferromagnetically, forming a 2D Heisenberg ferromagnet.

Most likely S=1 with four electrons per droplet.

Abstract

We argue that the magnetic susceptibility data, Refs. 1-3, for the low-density two-dimensional (2D) silicon-based electron gas indicate that magnetically active electrons are localised in spin-droplets. The droplets exist in both the insulating and metallic phases, and interact ferromagnetically, forming an effective 2D Heisenberg ferromagnet. Comparing the data with known analytical and numerical results for a 2D Heisenberg ferromagnet, we determine that JS^2 \approx 0.6K, where S is the spin of the droplet and J is the ferromagnetic exchange constant between droplets. We further argue that most likely S=1 with four electrons occupying each droplet on average. We discuss the dependence of the magnetic susceptibility and the specific heat on the external magnetic field, which follows from the model, and hence we suggest further experimental tests of the model.