Graphene Josephson Junctions with Narrowly Defined Trenches*

We present new results obtained from encapsulated graphene/boron-nitride heterostructure devices in which narrow trenches have been etched. These trenches are created both through e-beam lithography / reactive ion etching as well as through helium ion milling. We confirm cut widths on the order of tens of nanometers using scanning electron microscopy and atomic force microscopy. We report on several Josephson junction devices made by contacting these mesas with superconducting electrodes and demonstrate supercurrent in the quantum Hall regime. The dependence of this supercurrent on magnetic field is studied and compared to geometrical expectations.