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 EZ rivals the Thouless energy ETh, a regime hitherto inaccessible in graphene. As the parallel magnetic field H increases, the 2DJJ's critical current is suppressed and in a few cases undergoes suppression and recovery. We explore the behavior in H by considering theoretically two effects: a 0-π 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 as a newly accessible experimental knob.
Bibliographical noteFunding Information:
The authors wish to thank M. Aprili, Y. Oreg, A. Stern, F. Pientka, and A. Di Bernardo for illuminating discussions. This work was funded by a European Research Council Starting Grant (Grant No. 637298, TUNNEL), Israeli Science Foundation Grant No. 861/19, and BSF Grant No. 2016320. T.D. and A.Z. are grateful to the Azrieli Foundation for Azrieli Fellowships. K.W. and T.T. acknowledge support from the Elemental Strategy Initiative conducted by the MEXT, Japan, Grant No. JPMXP0112101001, JSPS KAKENHI Grant No. JP20H00354 and the CREST (Grant No. JPMJCR15F3), JST.
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