Tunable 0–π transition by interband coupling in iron-based superconductor Josephson junctions

Abstract

An extended four-component Bogoliubov–de Gennes equation is applied to study the Josephson effect in ballistic limit between either two iron-based superconductors (SCs) or an iron-based SC and a conventional s -wave SC, separated by a normal metal. A 0– π transition as a function of interband coupling strength α is always exhibited, arising from the tuning of mixing between the two trajectories with opposite phases. The novel property can be experimentally used to discriminate the ${s}_{\pm }$ -wave pairing symmetry in the iron-based SCs from the ${s}_{++}$ -wave one in MgB _2 . The effect of interface transparency on the 0– π transition is also presented. The 0– π transition as a function of α is wholly distinct from that as a function of barrier strength or temperature in recent theories (Linder et al 2009 Phys. Rev. B http://dx.doi.org/10.1103/PhysRevB.80.020503 80 http://dx.doi.org/10.1103/PhysRevB.80.020503 ). The possible experimental probe of the phase-shift effect in iron-based SC Josephson junctions is commented on as well.

Keywords

• tunable 0–π transition
• interband coupling
• iron-based superconductor Josephson junctions
• 74.20.Rp
• 74.50.+r
• 74.70.Xa