Tunable quantum interferometer for correlated moiré electrons.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Phenomena

Background:

• Magic-angle twisted bilayer graphene exhibits tunable correlated states, including superconductivity.
• Moiré devices allow studying superconductivity's nature and electron coherence.
• Fundamental coherence effects like Little-Parks and Aharonov-Bohm were previously unreported in moiré devices.

Purpose of the Study:

• To investigate fundamental coherence effects in moiré devices.
• To study the Little-Parks and Aharonov-Bohm effects in a single device.
• To probe the nature of superconductivity and electron coherence in magic-angle twisted bilayer graphene.

Main Methods:

• Fabrication of a gate-defined ring device in magic-angle twisted bilayer graphene.
• Embedding superconducting or normally conducting rings within correlated or band insulators.
• Applying magnetic fields and varying carrier density to observe quantum phenomena.

Main Results:

• Observation of the Little-Parks effect in the superconducting phase diagram, confirming an effective charge of 2e.
• Demonstration of the Aharonov-Bohm effect in a normally conducting ring.
• Measurement of coherence length exceeding several microns for conducting moiré electrons at 50 mK.
• Identification of a regime with h/e-periodic oscillations and superconductor-like nonlinear transport.

Conclusions:

• The study successfully observed both Little-Parks and Aharonov-Bohm effects in a single moiré device.
• The findings confirm the Cooper pair charge and reveal exceptionally long coherence lengths in moiré electrons.
• This work opens new avenues for exploring quantum phenomena in moiré superlattices.