Anomalous Josephson Coupling and High-Harmonics in Non-Centrosymmetric Superconductors with $S$-wave Spin-Triplet Pairing

TL;DR

This paper investigates how non-centrosymmetric superconductors with spin-triplet $s$-wave pairing exhibit anomalous Josephson effects, including high harmonics and $\

Contribution

It reveals the role of orbital-dependent spin-triplet order parameters and spin-orbit coupling in producing unconventional Josephson behaviors and $\",

Findings

Presence of high harmonics in current-phase relation.

Ground state can switch between 0 and $\\varphi$-phase.

Unconventional temperature and magnetic field dependence of critical current.

Abstract

We study the Josephson effects arising in junctions made of non-centrosymmetric superconductors with spin-triplet pairing having $s$-wave orbital-singlet symmetry. We demonstrate that the orbital dependent character of the spin-triplet order parameter determines its non-trivial texture in the momentum space due to the inversion symmetry breaking and spin-orbit interactions. The emergence of this pattern is responsible for the occurrence of an anomalous Josephson coupling and a dominance of high-harmonics in the current phase relation. Remarkably, due to the spin-orbital couplings, variations in the electronic structure across the heterostructure can generally turn the ground state of the junction from 0- to a generic value of the Josephson phase, thus realizing the so-called $\varphi$-junction. Hallmarks of the resulting Josephson behavior, apart from non-standard current-phase relation, are provided by an unconventional temperature and magnetic field dependence of the critical current. These findings indicate the path for the design of superconducting orbitronics devices and account for several observed anomalies of the supercurrent in oxide interface superconductors.