Planar graphene-NbSe2 Josephson junctions in a parallel magnetic field

Thin transition metal dichalcogenides sustain superconductivity at large in-plane magnetic fields due to Ising spin-orbit protection, which locks their spins in an out-of-plane orientation. Here we use thin NbSe2 as superconducting electrodes laterally coupled to graphene, making a planar, all van der Waals two-dimensional Josephson junction (2DJJ). We map out the behavior of these novel devices with respect to temperature, gate voltage, and both out-of-plane and in-plane magnetic fields. Notably, the 2DJJs sustain supercurrent up to parallel fields as high as 8.5 T, where the Zeeman energy E-Z rivals the Thouless energy E-Th, a regime hitherto inaccessible in graphene. As the parallel magnetic field H-parallel to increases, the 2DJJ's critical current is suppressed and in a few cases undergoes suppression and recovery. We explore the behavior in H-parallel to by considering theoretically two effects: a 0-pi transition induced by tuning of the Zeeman energy and the unique effect of ripples in an atomically thin layer which create a small spatially varying perpendicular component of the field. The 2DJJs have potential utility as flexible probes for two-dimensional superconductivity in a variety of materials and introduce high H-parallel to as a newly accessible experimental knob.

Automated summary

Researchers utilized thin NbSe2 as superconducting electrodes laterally coupled to graphene to form a planar van der Waals two-dimensional Josephson junction. By studying the behavior of these novel devices with respect to temperature, gate voltage, and magnetic fields, they found that the junctions could sustain supercurrent up to high parallel magnetic fields of 8.5 T.