Insulating state in tetralayers reveals an even-odd interaction effect in multilayer graphene

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Electronics

Background:

• Graphene multilayers exhibit electronic properties sensitive to electron-electron interactions near charge neutrality.
• While bilayers are predicted to become insulating due to these interactions, mono- and trilayers remain conductive.
• Thicker multilayers were expected to show weaker interaction effects, converging towards graphite behavior.

Purpose of the Study:

• To investigate the electronic properties of Bernal-stacked tetralayer graphene.
• To determine if electron-electron interactions induce insulating states in tetralayer graphene.
• To explain the observed phenomenology and its relation to other graphene multilayers.

Main Methods:

• Experimental investigation of Bernal-stacked tetralayer graphene.
• Analysis of electronic properties near charge neutrality.
• Comparison with theoretical predictions and experimental data from other graphene multilayers.

Main Results:

• An insulating state was observed in Bernal-stacked tetralayer graphene near charge neutrality.
• This insulating state is visible at higher temperatures compared to bilayer graphene.
• A systematic even-odd effect of interactions was identified across different Bernal-stacked layer thicknesses.

Conclusions:

• The insulating state in tetralayer graphene is driven by electron-electron interactions, contradicting expectations based on single-particle band structure.
• The findings suggest a generalization of interaction-driven, symmetry-broken states applicable to various Bernal-stacked graphene multilayers.
• The study highlights the complex role of electron-electron interactions in determining the electronic behavior of few-layer graphene systems.