Novel 0– π transitions in Josephson junctions between noncentrosymmetric superconductors

Abstract

We study the Josephson effect between two noncentrosymmetric superconductors (NCSs) with opposite polarization vectors of Rashba spin-orbit coupling (RSOC). We find a 0-π transition driven by the triplet-singlet ratio of NCSs. Different from conventional 0-π transitions, the Andreev bound states change their energy range instead of phase shift in the 0-π transition found here. This novel property results in a feature that the critical current becomes almost zero at the transition point, not only a minimum. Furthermore, when the directions of RSOC polarization vectors are the same in two NCSs, the similar effect can also be found in the presence of a perpendicular exchange field or a Dresselhause spin-orbit coupling in the interlayer. We find novel oscillations of critical current without 0-π transition. These novel 0-π transitions or oscillations of critical current present new understanding of the Josephson effect and can also serve as a tool to determine the unknown triplet-singlet ratio of NCSs.

The 0– π Phase Transition in Epitaxial NbN/Ni 60 Cu 40 /NbN Josephson Junctions

“…A 𝜋-phase shift has been theoretically predicted in Josephson junctions, involving heavy-fermion superconducting systems, [1] noncentrosymmetric superconductors, [2] and cuprate superconductors. [3] The formation of 𝜋-regions in grain boundary junctions is attributed to the combined effects of the dominant 𝑑 𝑥 2 −𝑦 2 wave order parameter symmetry of the YBa 2 Cu 3 O 7 and the faceted microstructure of the grain boundary.…”