Kagome electronic states in gradient-strained untwisted graphene bilayers.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Moiré superlattices in twisted bilayer graphene exhibit exotic electronic states like superconductivity and correlated insulators.
• Fabrication of twisted moiré superlattices often suffers from disorder, impacting reproducibility and control.

Purpose of the Study:

• To propose and investigate gradient strain as an alternative method for constructing moiré superlattices in untwisted bilayer graphene.
• To explore the electronic properties and structural characteristics of gradient strain-induced moiré superlattices (gs-BLG).

Main Methods:

• Utilized force-field and first-principles calculations to model gs-BLG.
• Analyzed interlayer-spacing distributions and electronic band structures.

Main Results:

• gs-BLG exhibits kagome-like interlayer-spacing distributions and strain-tunable kagome electronic bands.
• Three distinct forms of diatomic kagome lattices (subtle, pronounced, distorted) arise from competing strain effects.
• Kagome electronic bands near the Fermi level were identified, with tunable bandwidths and hopping parameters.

Conclusions:

• Gradient strain engineering provides a viable and reproducible alternative to twist engineering for creating moiré superlattices.
• gs-BLG offers a versatile platform for exploring emergent electronic phases and novel quantum phenomena.