Promotion of superconductivity in magic-angle graphene multilayers

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• Graphene moiré superlattices exhibit complex correlated insulating, topological, and superconducting phases.
• The origins of correlations and topology are linked to flat bands, but superconductivity remains poorly understood.

Purpose of the Study:

• To investigate superconductivity and flavor polarization in twisted multi- and pentalayer graphene on a transition metal dichalcogenide substrate.
• To explore the influence of layer number and band structure on emergent electronic phases.

Main Methods:

• Fabrication of magic-angle twisted tri-, quadri-, and pentalayer graphene devices on monolayer tungsten diselenide.
• Electrical transport measurements to probe insulating states and superconductivity.
• Analysis of the impact of electric displacement fields and carrier filling factors.

Main Results:

• Demonstrated flavor polarization and superconductivity in twisted graphene multilayers.
• Observed electric-field-induced insulating states in trilayer and quadrilayer graphene.
• Superconductivity emerged over an extended filling-factor range with increasing layer number, notably in pentalayer graphene.

Conclusions:

• The interplay between flat and dispersive bands is crucial for extending superconducting regions in graphene moiré superlattices.
• Layer engineering and substrate interactions offer pathways to tune and enhance superconductivity in moiré systems.