Electric field-tunable superconductivity in alternating-twist magic-angle trilayer graphene

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Phenomena

Background:

• Van der Waals (vdW) heterostructures with engineered moiré superlattices enable the study of novel quantum phenomena.
• Twisting layers in vdW heterostructures is a key method for creating tunable electronic properties.

Purpose of the Study:

• To construct and investigate a three-layer graphene vdW heterostructure with specific twist angles.
• To explore the emergence and characteristics of superconductivity in this engineered moiré system.

Main Methods:

• Fabrication of a vdW heterostructure with three graphene layers and alternating twist angles (±θ).
• Experimental observation of superconductivity at a twist angle near the predicted magic angle (θ ≈ 1.56°).
• Tuning of doping levels and displacement fields to study superconducting regimes.

Main Results:

• Observed displacement field-tunable superconductivity with a maximum critical temperature (Tc) of 2.1 Kelvin.
• Superconducting regimes correlated with flavor polarization of moiré bands and bounded by van Hove singularities (vHS).
• Experimental results deviate from weak coupling theories, indicating unconventional superconductivity.

Conclusions:

• The study demonstrates unconventional superconductivity in a three-layer graphene moiré superlattice.
• The findings highlight the role of moiré band structure, flavor polarization, and vHS in unconventional superconductivity.
• This work opens new avenues for exploring exotic quantum states in twisted van der Waals materials.