Interstitial-Induced Ferromagnetism in a Two-Dimensional Wigner Crystal

Area of Science:

• Condensed Matter Physics
• Quantum Mechanics
• Materials Science

Background:

• The two-dimensional Wigner crystal (WC) exhibits ferromagnetism in the strongly interacting regime (r_{s}≫1) of the two-dimensional electron gas (2DEG).
• Previous studies reported high-temperature ferromagnetism in AlAs quantum wells, exceeding predicted exchange energies for pure WCs.

Purpose of the Study:

• To analyze the dynamics of an interstitial defect within a WC.
• To investigate the impact of this defect on magnetic properties and energy scales.

Main Methods:

• Analysis of large r_{s} dynamics of an interstitial defect in a WC.
• Identification of dominant hopping processes contributing to magnetism.

Main Results:

• An interstitial defect induces local ferromagnetism with significantly higher energy scales.
• Three dominant hopping processes favor a large, fully polarized ferromagnetic polaron.
• The defect's influence on magnetism is observed at temperatures orders of magnitude higher than predicted for pure WCs.

Conclusions:

• Interstitial defects play a crucial role in the high-temperature ferromagnetism observed in 2DEGs.
• The findings provide a potential explanation for the discrepancy between experimental observations and theoretical predictions for WC magnetism.
• Speculation on the phenomenology of magnetism near the metal-insulator transition of the 2DEG.