Graphene Josephson junctions in high in-plane magnetic field*

In recent years, there is a growing interest in graphene as the main ingredient in Josephson junctions (JJs). The ability to control the concentration and the sign of the charge carriers allows the fabrication of bipolar JJ with critical currents that can be varied in three orders of magnitude in the same device. Also, using clean graphene allows studying the interplay between quantum Hall effect and superconductivity. The study of graphene JJs in high magnetic fields was so far limited by the response of the host superconductor to the application of field. We fabricate JJs using ultra-thin NbSe₂ as the superconductor, allowing us to apply very high in-plane magnetic fields without significantly affecting the superconducting gap. We show that such JJs, NbSe₂- graphene-NbSe₂, are highly transparent, and survive to in-plane fields up-to 8T. Due to the two-dimensional nature of the system, the interaction of the in-plane field with the system occurs only with the spin degree of freedom, imitating S-ferromagnet-S JJs, with effective exchange energy determined by the external field.