Controllable 0-π Transition in a Superconducting Graphene-Nanoribbon Junction

The supercurrent in a Josephson junction composed of the zigzag edged graphene nanoribbon (ZGNR) lying between two superconducting leads [superconductor-graphene-superconductor (SGS) junction] has been studied by the Green’s function method. It is found that a small transverse electric field applied on the ZGNR can reverse the supercurrent direction, leading to a so-called 0-π phase transition. The 0-π phase transition can happen periodically with a change in the ZGNR’s length, and, more importantly, can be easily and electrically controllable by a gate voltage, which is absent in the conventional superconducting π junction and would make the SGS junction very promising for future application in superconducting electronics, as well as quauntum information and computation.