Controllable 0 - π transition in iron pnictide superconductor junctions with a spacer of strong ferromagnet

摘要

We investigate the control of 0 - π transition in Josephson junctions consisting of a highly spin-polarized ferromagnet coupled to two iron pnictide superconductors (SCs). It is shown that, a 0 - π transition as a function of interband coupling strength is always exhibited, which can be experimentally used to discriminate the s±-wave pairing symmetry in the iron pnictide SCs from the s_(++)-wave one in MgB_2. By tuning the doping level in the s±-wave SCs, one can vary the interband coupling strength so as to obtain the controllable 0 - π transition. This device may be realized with current technologies and has practical use in Cooper pair spintronics and quantum information.