Wigner Glass, Spin-liquids, and the Metal-Insulator Transition

TL;DR

This paper proposes a new phase diagram for two-dimensional electron gases, introducing the Wigner Glass as the insulating state and describing the metal-insulator transition as its melting, with distinct magnetic phases and non-Fermi liquid behavior on the metallic side.

Contribution

It introduces the concept of Wigner Glass as the insulating phase and describes the transition as melting of this phase, incorporating magnetic states and non-Fermi liquid properties.

Findings

Identification of Wigner Glass as the insulating phase.

Description of the transition as melting of the Wigner Glass.

Prediction of non-Fermi liquid behavior on the metallic side.

Abstract

Recent experiments on the two dimensional electron gas in various semiconductor devices have revealed an unexpected metal-insulator transition and have challenged the previously held assumption that there is no such transition in two dimensions. While the experiments are still at the stage of rapid development, it is becoming evident that they cannot be understood from the conventional perspective of weak interactions. In the present paper, we propose the following. (1) The low-density insulating state is the Wigner Glass, a phase with quasi-long-range translational order and competing ferromagnetic and antiferromagnetic spin-exchange interactions. (2) The transition is the melting of this Wigner Glass, disorder being the agent allowing the transition to be second order. (3) Within the Wigner Glass phase, there are at least two, distinct magnetic ground-states, a ferromagnetic state at very low electron density and a spin-liquid state with a spin pseudo-gap at higher densities. (4) The metallic side of the transition is a non-Fermi liquid. These conclusions are encapsulated in Figure 1 which presents the proposed phase diagram as a function of disorder strength and density; we also suggest experimental signatures of the various phases and transitions.