Layer-polarized ferromagnetism in rhombohedral multilayer graphene

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Phenomena

Background:

• Strongly correlated electron systems exhibit diverse quantum phenomena like superconductivity and magnetism.
• Rhombohedral multilayer graphene possesses topologically protected surface flat bands, but their study is complicated by interactions with high-energy bands.

Purpose of the Study:

• To develop a method for isolating surface flat bands in rhombohedral multilayer graphene.
• To investigate the emergence of correlated surface states and their associated phenomena.
• To explore the potential for controlling magnetic properties in these systems.

Main Methods:

• Fabrication of moiré superlattices on rhombohedral multilayer graphene.
• Utilizing moiré potential modulation to decouple surface and high-energy bands.
• Applying displacement fields to tune electronic properties and induce polarization.
• Measuring the anomalous Hall effect to detect ferromagnetism.

Main Results:

• Moiré superlattices successfully isolated the surface flat bands, confirmed by screening effects indicating electronic decoupling.
• Isolated flat bands promoted correlated surface states away from charge neutrality points.
• Tunable, layer-polarized ferromagnetism was observed, evidenced by a hysteretic anomalous Hall effect.

Conclusions:

• Moiré superlattices provide an effective platform for isolating and studying surface flat bands in rhombohedral multilayer graphene.
• The findings demonstrate the potential for engineering correlated surface states and achieving tunable magnetism.
• This work paves the way for exploring novel quantum phenomena in flat-band systems.