Quasi-Φ₀-Periodic Supercurrent at Quantum Hall Transitions

Area of Science:

• Condensed Matter Physics
• Quantum Materials
• Topological Quantum Computation

Background:

• The synergy between superconductivity and the quantum Hall (QH) effect is crucial for advancing topological quantum computation.
• Previous studies indicated QH edge states could mediate supercurrents in graphene weak links.

Purpose of the Study:

• To report the observation of a supercurrent linked to transitions between adjacent QH plateaus in graphene.
• To investigate the transport regime of percolative supercurrents in van der Waals devices.

Main Methods:

• Fabrication of a back-gated graphene Josephson junction using high-mobility CVD-grown graphene encapsulated in hexagonal Boron Nitride (hBN).
• Contacting the graphene with Nb leads to form the Josephson junction.
• Employing quantum interference studies and magnetic field sweeps to observe supercurrents.

Main Results:

• Observation of a supercurrent associated with transitions between adjacent QH plateaus, with transport paths in the compressible bulk.
• Detection of superconducting pockets persisting up to 2.4 T, near the Nb contacts' critical field.
• Observation of an approximate Φ₀ = h/2e periodicity of the QH-supercurrent with magnetic field, indicating interference in a proximitized percolative phase.

Conclusions:

• The study demonstrates a novel experimental platform for investigating percolative supercurrents in graphene.
• The findings contribute to the understanding of hybrid superconducting-topological states for quantum technologies.
• The flexibility of van der Waals devices offers new avenues for exploring exotic quantum phenomena.