Signature of Anomalous Andreev bound states in magnetic Josephson junction of noncentrosymmetric superconductor on a topological insulator

TL;DR

This paper investigates the Josephson effect in a noncentrosymmetric superconductor/half-metal junction on a topological insulator, revealing signatures of anomalous Andreev bound states, band splitting, and controllable Majorana modes influenced by magnetic and structural parameters.

Contribution

It introduces the study of anomalous Andreev bound states and Majorana modes in a topological insulator-based Josephson junction with noncentrosymmetric superconductors, highlighting the effects of magnetic misalignment and spin-orbit coupling.

Findings

Detection of 4π periodic ABS with parallel magnetic moments.

Observation of 2π periodic ABS with anti-parallel misalignment.

Critical current varies with singlet-triplet mixing and barrier transparency.

Abstract

We study the Josephson effect in a clean noncentrosymmetric superconductor/half-metal/noncentrosymmetric superconductor junction, which is grown on the surface of a three-dimensional Topological Insulator (TI) in the ballistic limit. We find the signature of anomalous Andreev Bound States (ABS) and band splitting for a spin-active barrier whose barrier magnetic moment is misaligned with the bulk moment. The chiral Majorana mode and 4$\pi$ periodic ABS are found to exist on the surface of TI for parallel orientation of the moments in the normal incidence condition. But for anti-parallel misalignment, we observe the 2$\pi$ periodic ABS. There exist a gap in ABS for oblique incidence. We find the splitting of Andreev levels in the presence of RSOC and also for unequal mixing of singlet-triplet correlations present in NCSC. The Majorana mode, ABS and Josephson supercurrent can be controlled by the ratio of barrier magnetic and non-magnetic moments. The critical current is found to be maximum for singlet or triplet dominated NCSC, while it is minimum in the equal mixing condition. The ABS is found to be barrier thickness dependent and is suppressed for an opaque barrier. We observe a monotonic decay in critical current with a finite length of the junction for all the singlet-triplet mixings and magnetic moments. The current-phase relation is found to be sinusoidal with no phase shift in the half-metallic limit, however, for different orientations of the bulk moment, an anomalous characteristic is also observed.