Competing correlated states around the zero field Wigner crystallization transition of electrons in two-dimensions

TL;DR

This study investigates the low-temperature phases of a high-mobility two-dimensional electron system, revealing competing metallic and insulating states, including a Wigner crystallization transition at high interaction strength, with detailed experimental analysis aligning with advanced theoretical models.

Contribution

It provides experimental evidence for a Wigner crystallization transition in a 2D electron system at high interaction parameter, matching quantum Monte Carlo predictions and exploring new spin-polarized states.

Findings

Identification of a Wigner crystallization transition at r_s~30.

Discovery of a low temperature partially spin-polarized state.

Agreement with quantum Monte Carlo phase diagram of the ideal jellium model.

Abstract

The competition between kinetic energy and Coulomb interactions in electronic systems can lead to complex many-body ground states with competing superconducting, charge density wave, and magnetic orders. Here we study the low temperature phases of a strongly interacting zinc-oxide-based high mobility two dimensional electron system that displays a tunable metal-insulator transition. Through a comprehensive analysis of the dependence of electronic transport on temperature, carrier density, in-plane and perpendicular magnetic fields, and voltage bias, we provide evidence for the existence of competing correlated metallic and insulating states with varying degrees of spin polarization. Our system features an unprecedented level of agreement with the state-of-the-art Quantum Monte Carlo phase diagram of the ideal jellium model, including a Wigner crystallization transition at a value of the interaction parameter $r_s\sim 30$ and the absence of a pure Stoner transition. In-plane field dependence of transport reveals a new low temperature state with partial spin polarization separating the spin unpolarized metal and the Wigner crystal, which we examine against possible theoretical scenarios such as an anti-ferromagnetic crystal, Coulomb induced micro-emulsions, and disorder driven puddle formation.