中文摘要：

文章作者利用实空间格林函数方法研究了超导体-zigzag边纳米石墨带-超导体（SGS）约瑟夫森结中的超导输运行为．结果发现：（1）通过一个外加横向电场可以使该超导结的超流方向发生翻转，即发生超导O-π相变；（2）通过改变纳米石墨带的长度或者其上的门电压，同样也可以使它发生O-π相变．由于可以用外电场方便地控制该超导结O-π相变的发生，使得它有可能在未来的量子计算以及超导电子学中发挥巨大的作用．

英文摘要：

The supercurrent in a Josephson junction composed of a 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 applying a small transverse electric field can reverse the supercurrent direction, leading to a so - called O-π phase transition. This transition can also happen periodically with a given change in the ZGNR＇s length, and, more importantly, can be easily and electrically controllable by a gate voltage, which is not possible in conventional superconducting π junctions and makes the SGS junction very promising for future application in superconducting electronics, as well as in quantum information and computation.