Josephson junctions of Weyl and multi-Weyl semimetals

We study a Josephson junction involving a Weyl and a multi-Weyl semimetal separated by a barrier region of width d created by putting a gate voltage U-0 over the Weyl semimetal. The topological winding number of such a junction changes across the barrier. We show that IcRN for such junctions, where I-c is the critical current and R-N the normal-state resistance, in the thin-barrier limit, has a universal value independent of the barrier potential. We provide an analytical expression of the Andreev bound states and use it to demonstrate that the universal value of IcRN is a consequence of change in topological winding number across the junction. We also study the AC Josephson effect in such a junction in the presence of an external microwave radiation, chart out its current-voltage characteristics, and show that the change in the winding number across the junction shapes the properties of its Shapiro steps. We discuss the effect of increasing barrier thickness d on the above-mentioned properties and chart-out experiments which may test our theory.