Graphene Junctions Sustain Josephson Effect Up To 6 Tesla

Researchers led by A. D’iez-Carlón have demonstrated sustained phase-coherent Josephson interference in graphene junctions at a magnetic field strength of 6 Tesla, a level exceeding the range expected for conventional ballistic graphene junctions. The team achieved this high-field superconductivity by engineering ballistic graphene/hBN junctions, effectively reshaping how electrons behave under strong magnetic fields. Their work reveals that this specific spectral pattern transforms Landau levels, creating dispersive magnetic Bloch bands with finite quasiparticle group velocity that support extended electron-hole trajectories. According to the researchers, these junctions demonstrate phase-coherent Andreev transport not only across the primary Dirac cone but also within the reconstructed moiré minibands, establishing a new platform for high-field superconducting interferometry.

This achievement hinges on the utilization of moiré-engineered graphene, where the structure appears to counteract the field-suppressing effects typically observed in Josephson transport. The authors state that their results show Hofstadter minibands can stabilize phase-coherent superconductivity deep into the parameter domain conventionally associated with the quantum Hall regime, suggesting a new avenue for high-field superconducting interferometry. This stabilization opens possibilities for more sensitive and robust superconducting devices operating in challenging magnetic environments.

Researchers are now demonstrating phase-coherent Josephson interference in graphene-based junctions at magnetic field strengths previously considered insurmountable, pushing the boundaries of superconducting interferometry. Utilizing ballistic graphene/hBN junctions, the team, led by A. D’iez-Carlón, found that this transformation allows for Andreev transport and Fraunhofer interference to persist even as magnetic fields increase. This new platform promises to advance the field by enabling measurements in conditions where coherence would normally be lost, according to the published findings.