Critical Filling Factor for the Formation of a Quantum Wigner Crystal Screened by a Nearby Layer

TL;DR

This study measures how the presence of a nearby high-density electron layer affects the critical filling factor for the formation of a quantum Wigner crystal in a dilute two-dimensional electron system, revealing a strong dependence on interlayer distance.

Contribution

It demonstrates that screening from a nearby electron layer significantly lowers the critical filling factor for Wigner crystal formation in 2D systems.

Findings

Wigner crystal forms at smaller filling factors with a nearby layer.

Critical filling factor depends strongly on interlayer distance.

Screening effects alter the phase transition conditions.

Abstract

One of the most fascinating ground states of an interacting electron system is the so-called Wigner crystal where the electrons, in order to minimize their repulsive Coulomb energy, form an ordered array. Here we report measurements of the critical filling factor ($\nu_{C}$) below which a magnetic-field-induced, quantum Wigner crystal forms in a dilute, two-dimensional electron layer when a second, high-density electron layer is present in close proximity. The data reveal that the Wigner crystal forms at a significantly smaller $\nu_{C}$ compared to the $\nu_{C}$ ($\simeq 0.20$) in single-layer two-dimensional electron systems. The measured $\nu_{C}$ exhibits a strong dependence on the interlayer distance, reflecting the interaction and screening from the adjacent, high-density layer.