Supercurrent reversal in Zeeman-split Josephson junctions

Abstract

We theoretically study the current-phase relation in a Josephson junction comprising the Zeeman-split superconductors (ZSs) and a normal metal (N). We show that at low temperatures the Josephson current in the∈ ZS/N/ZS junctions exhibits a supercurrent reversal at a certain phase difference ϕc (0, π). By calculating the spectral Josephson

current, we demonstrate that the band splitting due to the Zeeman interaction causes the level crossing in the spectra of the Andreev bound states and the sign reversal of the Josephson current, similar to the known case of an SFIFS junction (F is a ferromagnet, I is an insulator). Additionally, we propose an alternative method to observe the supercurrent reversal. We have demonstrated that ϕ c depends on the Rashba spin-orbit interaction in the normal segment. The spin precession of a quasiparticle due to the spin-orbit interaction modifies the energy spectra of the Andreev levels and ϕc. In experiments, the amplitude of the spin-orbit interaction is tunable by applying the gate voltage. Therefore, by measuring the CPR by tuning the spin-orbit coupling, one would be able to observe the anomalous current reversal.