Ballistic graphene Josephson junctions from the short to the long regime
  We investigate the critical current, $I_C$, of ballistic Josephson junctions made of encapsulated graphene/boron-nitride heterostructures. We observe a crossover from the short to the long junction regimes as the length of the device increases. In long ballistic junctions, $I_S$ is found to scale as $\propto \exp(-k_bT/\delta E)$. The extracted energies $\delta E$ are independent of the carrier density and proportional to the level spacing of the ballistic cavity, as determined from Fabry-Perot oscillations of the junction normal resistance. As $T\rightarrow 0$ the critical current of a long (or short) junction saturates at a level determined by the product of $\delta E$ (or $\Delta$) and the number of the junction's transversal modes. 
I. V. Borzenets, F. Amet, C. T. Ke, A. W. Draelos, M. T. Wei, A.   Seredinski, K. Watanabe, T. Taniguchi, Y. Bomze, M. Yamam...
cond-mat.mes-hall