High Magnetic Field Stability in a Planar Graphene-NbSe₂ SQUID

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Niobium diselenide (NbSe2) exhibits superconductivity even at high in-plane magnetic fields.
• Atomically thin van der Waals heterostructures offer unique electronic properties.
• Superconducting Quantum Interference Devices (SQUIDs) are sensitive magnetic flux detectors.

Purpose of the Study:

• To construct and characterize a novel, atomically thin, all van der Waals SQUID.
• To investigate the behavior of superconductivity in NbSe2 at high magnetic fields.
• To demonstrate sub-nanometer sensitivity in current distribution measurements.

Main Methods:

• Fabrication of an all van der Waals SQUID using NbSe2 contacts and graphene weak links.
• Measurement of critical current interference patterns as a function of in-plane magnetic field up to 4.5 T.
• Analysis of current distribution evolution under high magnetic fields.

Main Results:

• The 2D planar SQUID demonstrated unique stability at high in-plane magnetic fields.
• Critical current interference patterns were traced, revealing the evolution of current distribution.
• Sub-nanometer sensitivity to current flow deviations was achieved, showing a field-driven redistribution of supercurrent into a narrow channel.
• A new application for asymmetric SQUID geometry to probe current density without phase information was proposed.

Conclusions:

• Atomically thin NbSe2-based van der Waals SQUIDs are stable and sensitive probes of superconductivity.
• High magnetic fields induce significant changes in supercurrent distribution in thin NbSe2.
• Asymmetric SQUID geometry offers a novel method for direct current density probing.