Unconventional ferroelectricity in moiré heterostructures.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• Emergent phenomena in quantum materials are key to condensed-matter research.
• Ferroelectricity, characterized by switchable electric dipoles, is typically observed in materials with separated charge centers.

Purpose of the Study:

• To investigate emergent ferroelectricity in graphene-based moiré heterostructures.
• To explore the potential of carbon-based materials for novel electronic applications.

Main Methods:

• Fabrication of Bernal-stacked bilayer graphene encapsulated by hexagonal boron nitride layers.
• Introduction of a moiré superlattice potential.
• Systematic transport measurements as a function of displacement field and electron filling.
• Probing ferroelectric polarization using a non-local monolayer graphene sensor.

Main Results:

• Observation of switchable ferroelectricity in the graphene moiré heterostructure.
• Prominent and robust hysteretic behavior of graphene resistance with an applied out-of-plane displacement field.
• Evidence of unconventional, odd-parity electronic ordering.

Conclusions:

• Graphene-based moiré heterostructures exhibit emergent ferroelectricity.
• This discovery opens possibilities for ultrafast, programmable, and atomically thin carbon-based memory devices.