Tunability of Andreev levels via spin-orbit coupling in Zeeman-split Josephson junctions

TL;DR

This paper investigates how the energy levels in Zeeman-split Josephson junctions can be tuned by manipulating Rashba spin-orbit interaction and magnetic field orientation, revealing controllable band splitting and asymmetric phase relations.

Contribution

It provides a theoretical demonstration of tunable Andreev levels via spin-orbit coupling and magnetic field orientation in Zeeman-split Josephson junctions, highlighting new control mechanisms.

Findings

Andreev levels are tunable by Rashba interaction strength and wire length.

The band splitting magnitude depends on spin precession in the Rashba wire.

The $ ext{I}$-$ ext{V}$ characteristics remain invariant despite changes in Andreev reflection processes.

Abstract

We study Andreev reflection and Andreev levels $\varepsilon$ in Zeeman-split superconductor/Rashba wire/Zeeman-split superconductor junctions by solving the Bogoliubov de-Gennes equation. We theoretically demonstrate that the Andreev levels $\varepsilon$ can be controlled by tuning either the strength of Rashba spin-orbit interaction or the relative direction of the Rashba spin-orbit interaction and the Zeeman field. In particular, it is found that the magnitude of the band splitting is tunable by the strength of the Rashba spin-orbit interaction and the rength of the wire, which can be interpreted by a spin precession in the Rashba wire. We also find that if the Zeeman field in the superconductor has the component parallel to the direction of the junction, the $\varepsilon$-$\phi$ curve becomes asymmetric with respect to the superconducting phase difference $\phi$. Whereas the Andreev reflection processes associated with each pseudospin band are sensitive to the relative orientation of the spin-orbit field and the exchange field, the total electric conductance interestingly remains invariant.