The Andreev-Ising-Josephson Diode

Transition-metal dichalcogenides featuring Ising spin-orbit coupling in so-called Ising superconductors offer a unique system to study the interplay of superconductivity and magnetism. The presence of spin-triplet correlations, spectral properties such as the mirage gap, and the field-tunable charge and spin currents in Ising-superconductor Josephson junctions are some of the important features. We first study an Ising-superconductor Josephson junction with a perfectly transparent nonmagnetic barrier. The spin-degenerate Andreev bound states are split due to the relative orientation of the in-plane fields within the superconductors of the junction. The current-phase relations display a highly non-sinusoidal behavior. Introducing an additional ferromagnetic barrier with low transmission in each channel creates a Josephson junction with a nonreciprocal current-phase relation, showcasing a diode effect. The diode efficiency is highly tunable with the relative magnetization angle and the conductance ratio between the ferromagnetic and nonmagnetic barriers.

Previous work on the subject:

G. Tang, C. Bruder, and W. Belzig, Magnetic field-induced “mirage” gap in an Ising superconductor, Phys. Rev. Lett. 126, 237001 (2021).

G. Tang, R. L. Klees, C. Bruder, and W. Belzig, Controlling charge and spin transport in an Ising-superconductor Josephson junction, Phys. Rev. B 104, L241413 (2021).

S. Patil, G. Tang, and W. Belzig, Spectral properties of a mixed singlet-triplet Ising superconductor, Front. Electron. Mater. 3, 1254302 (2023).